West Nile Virus Outbreak: Lessons for Public Health Preparedness (Letter
Report, 09/11/2000, GAO/HEHS-00-180).
Pursuant to a congressional request, GAO provided information on the
West Nile virus outbreak, focusing on: (1) establishing a thorough
chronological account of the significant events and communications that
occurred, from doctors and others who first saw the symptoms and from
the officials mounting a response; and (2) identifying lessons learned
for public health and bioterrorism preparedness.
GAO noted that: (1) the analysis of the West Nile virus outbreak began
as two separate investigations--one of sick people, the other of dying
birds; (2) on the human side, the investigation began quickly after a
physician at a local hospital reported the first cases, and the original
diagnosis, while incorrect, led to prompt mosquito control actions by
New York City officials; (3) the ongoing investigation involved the
combined efforts of many people in public health agencies and research
laboratories at all levels of government; (4) a consensus that the bird
and human outbreaks were linked, which was a key to identifying the
correct source, took time to develop and was initially dismissed by many
involved in the investigation; (5) when the bird and human
investigations converged several weeks after initial diagnosis, and
after laboratory research was launched independently by several of the
participants to explore other possible causes, the link was made and the
virus was correctly identified; (6) there are several key lessons that
emerged from the investigation and response to this outbreak; (7) the
local disease surveillance and response system is critical; (8) in this
outbreak, many aspects of the local surveillance system worked well, in
that the outbreak was quickly spotted and immediately investigated; (9)
assessments of the infrastructure for responding to outbreaks suggest
that surveillance networks in many other locations may not be as well
prepared; (10) better communication is needed among public health
agencies; (11) as the investigation grew, lines of communication and
decision-making were often unclear, and efforts to keep everyone
informed were awkward; (12) links between public and animal health
agencies are becoming more important; (13) the length of time it took to
connect the bird and human outbreaks of the West Nile virus signals a
need for better coordination among public and animal health agencies;
(14) ensuring adequate laboratory capabilities is essential; (15) even
though this was a relatively small outbreak, it strained resources for
several months; (16) because a bioterrorist event could look like a
natural outbreak, bioterrorism preparedness rests in large part on
public health preparedness; and (17) the ensuing investigation and
post-outbreak assessments illustrate the challenges in identifying the
source of an outbreak, supporting public health officials' views that
public health preparedness is a key element of bioterrorism
preparedness.
--------------------------- Indexing Terms -----------------------------
REPORTNUM: HEHS-00-180
TITLE: West Nile Virus Outbreak: Lessons for Public Health
Preparedness
DATE: 09/11/2000
SUBJECT: Public health research
Disease detection or diagnosis
Federal/state relations
Animal diseases
Interagency relations
Infectious diseases
Emergency preparedness
IDENTIFIER: West Nile Virus
New York (NY)
St. Louis (MO)
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GAO/HEHS-00-180
Appendix I: Methodology
38
Appendix II: Timeline of Key Dates and Events in the West Nile Virus
Outbreak, 1999
40
Appendix III: Related Publications
59
Appendix IV: Comments From the Centers for Disease Control and Prevention
63
Appendix V: Comments From the New York City Department
of Health
65
Table 1: Examples of Surveillance and Laboratory Workload
Experienced by Selected Involved Agencies During and
Since the West Nile Outbreak 13
Table 2: Detailed Chronology of Events in the West Nile Virus
Outbreak, 1999 40
Figure 1: Transmission of St. Louis and West Nile Viruses 6
Figure 2: Timeline of 1999 West Nile Virus Outbreak 9
Figure 3: Examples of Migratory Patterns of Three Bird Species Susceptible
to West Nile 16
APHIS Animal and Plant Health Inspection Service
CDC Centers for Disease Control and Prevention
DNA deoxyribonucleic acid
ELISA enzyme-linked immunoabsorbent assay
E. coli Escherichia coli
FBI Federal Bureau of Investigation
HHS Department of Health and Human Services
NYC New York City
NYS New York State
PCR polymerase chain reaction
ProMED Program for Monitoring Emerging Diseases
RNA ribonucleic acid
USDA U.S. Department of Agriculture
USGS U.S. Geological Survey
Health, Education,
and Human Services Division
B-285899
September 11, 2000
The Honorable Daniel Patrick Moynihan
The Honorable Charles E. Schumer
United States Senate
The Honorable Gary L. Ackerman
The Honorable Joseph Crowley
The Honorable Eliot L. Engel
The Honorable Vito J. Fossella, Jr.
The Honorable Carolyn B. Maloney
The Honorable Jerrold L. Nadler
The Honorable Major R. Owens
The Honorable Charles B. Rangel
The Honorable Jose E. Serrano
The Honorable Edolphus Towns
The Honorable Anthony D. Weiner
House of Representatives
In the fall of 1999 the mosquito-borne West Nile virus--a virus never before
seen in this hemisphere--killed seven people in the New York City area and
made dozens more very sick. It was initially misidentified as a different,
related mosquito-borne virus often found in the United States. The incorrect
diagnosis did not significantly affect the appropriateness of spraying and
other mosquito control steps quickly begun in response. Even so, the
outbreak can serve as a source of lessons about how public health officials
can be better prepared in responding to potential crises involving uncertain
causes. And although the outbreak is considered to have been a natural
occurrence--possibly introduced by international travelers, migrating birds,
or mosquitoes accidentally brought from abroad--it can also provide lessons
about detecting and responding to an act of biological terrorism.
You asked us to review this outbreak and the response to it. We focused our
efforts on the following:
� establishing a thorough chronological account of the significant events
and communications that occurred, from doctors and others who first saw the
symptoms and from the officials mounting a response, and
� identifying lessons learned for public health and bioterrorism
preparedness.
We interviewed key officials, reviewed existing studies and reports,
assembled a detailed chronology of what occurred, and discussed the
implications of our findings with a wide range of agency and area officials.
We asked officials to provide documentation to the extent possible for key
decisions or events; however, to some extent the chronology of events is
based on officials' recollections of the dates that particular events
occurred. Appendix I describes our methodology in more detail. We conducted
our work from May through August 2000 in accordance with generally accepted
government auditing standards.
The analysis of the West Nile virus outbreak began--and for several weeks
continued--as two separate investigations: one of sick people, the other of
dying birds. On the human side, the investigation began quickly after a
physician at a local hospital reported the first cases, and the original
diagnosis, while incorrect, led to prompt mosquito control actions by New
York City officials. The ongoing investigation involved the combined efforts
of many people in public health agencies and research laboratories at all
levels of government. A consensus that the bird and human outbreaks were
linked, which was a key to identifying the correct source, took time to
develop and was initially dismissed by many involved in the investigation.
When the bird and human investigations converged several weeks after the
initial diagnosis, and after laboratory research was launched independently
by several of the participants to explore other possible causes, the link
was made and the virus was correctly identified.
Key lessons that emerge from the investigation and response to this outbreak
are as follows:
� The local disease surveillance and response system is critical. In public
health, surveillance is the ongoing collection, analysis, and interpretation
of health-related data. In this outbreak, many aspects of the local
surveillance system worked well, in that the outbreak was quickly spotted
and immediately investigated. Assessments of the infrastructure for
responding to outbreaks suggest that surveillance networks in many other
locations may not be as well prepared.
� Better communication is needed among public health agencies. As the
investigation grew, lines of communication and decision-making were often
unclear, and efforts to keep everyone informed were awkward (such as
conference calls that lasted for hours and involved dozens of people). Many
officials reported problems in this area.
� Links between public and animal health agencies are becoming more
important. Many emerging diseases, including West Nile, affect both animals
and humans. So do many viruses or other disease-causing agents that might be
used in bioterrorist attacks. The length of time it took to connect the bird
and human outbreaks of the West Nile virus signals a need for better
coordination among public and animal health agencies.
� Ensuring adequate laboratory capabilities is essential. Even though this
was a relatively small outbreak, it strained resources for several months.
Officials said there is a need for broadening laboratory capabilities,
ensuring adequate staffing and expertise, and improving the ability to deal
with surges in testing needs. These concerns point out the importance of
ensuring adequate networks between public health and other types of
laboratories, and of completing assessments of what laboratory capacity is
needed and what capacity is available.
� Because a bioterrorist event could look like a natural outbreak,
bioterrorism preparedness rests in large part on public health preparedness.
While the West Nile virus outbreak is considered by the Centers for Disease
Control and Prevention (CDC) and others to have been a naturally occurring
event, at one point there was speculation that it might have had an
unnatural (bioterrorist) origin. The ensuing investigation and post-outbreak
assessments illustrate the challenges in identifying the source of an
outbreak, supporting public health officials' views that public health
preparedness is a key element of bioterrorism preparedness.
Identified in 1937 and named after the Ugandan province where its discovery
took place, West Nile virus has a widespread distribution in Africa, West
Asia, and the Middle East, occasionally causing epidemics also in Europe.
Many people infected with the virus do not become ill or show symptoms, and
even when they do, symptoms may be limited to a headache, sore throat,
backache, or fatigue. Because no effective antiviral drugs have been
discovered, treatment for those who do become seriously ill can only attempt
to address symptoms such as swelling of the brain (encephalitis) and other
complications such as bacterial pneumonia. Fatality rates--the percentage of
people with confirmed infections who have died--have ranged from 3 to 15
percent for West Nile and are highest in the elderly.
The virus that was originally misidentified as the cause of the New York
outbreak is called St. Louis virus. Both West Nile and St. Louis
encephalitis viruses are in a group called "flaviviruses," and can be spread
when mosquitoes bite birds (often a natural host for the virus), acquire the
virus, and then pass it on to humans (see fig. 1). St. Louis encephalitis is
found in nature through much of the lower 48 states and is the most common
mosquito-borne virus causing outbreaks of human disease in the United
States. About 30 confirmed cases occur on average each year during
non-outbreak years. St. Louis encephalitis is also similar to West Nile in
that most people infected with it show no symptoms, but for those who become
seriously ill, no effective antiviral drugs are available. St. Louis
encephalitis has a slightly higher fatality rate than West Nile, ranging
from 3 to 30 percent of confirmed cases.
Rapid and accurate diagnosis of disease outbreaks is essential for many
reasons. It can help contain an outbreak quickly by allowing health
officials to implement appropriate control or prevention measures and
provide the most effective treatment for those who are affected. Rapid and
accurate diagnosis is essential not only for the public at large, but also
for health care workers and others who work with patients and laboratory
samples. Accurate diagnosis is also important in providing information that
could help determine whether the outbreak could have been deliberate--an act
of bioterrorism. Public health officials use the term "surveillance" to
denote the ongoing effort to collect, analyze, and interpret health-related
data so that public health actions can be planned, implemented, and
evaluated.
Local health personnel are likely to be the front line of response. Local
and state health departments might be the first to recognize unusual
patterns of illnesses. For example, an epidemiologist (a health official
trained to investigate diseases of unknown origin) in a city health
department might receive phone calls from nurses, doctors, or emergency room
personnel about increasing numbers of patients with similar symptoms. If the
problem is thought to be widespread or suspicious in origin, the local
health department is likely to involve the state health department, which is
responsible for statewide surveillance and investigations involving multiple
locations. The local and state response may also involve emergency
management personnel. Current protocols recommend that law enforcement
officials be notified if a case or series of cases have a suspicious origin.
Local, state, and federal laboratories also play a vital role. Initially,
this role may be to determine whether the unusual cases have the same
pathogen (the specific causative agent for the disease), and if so, to
identify it. Once an outbreak is established, laboratories may be called
upon to test samples such as blood or spinal fluid from persons with similar
symptoms, to determine who has the illness and the extent of the problem.
At the federal level, CDC, an agency of the Department of Health and Human
Services (HHS), is available upon request to help state and local officials
investigate the nature and origin of disease outbreaks. For example, CDC
maintains several laboratories that identify unusual or exotic viruses and
other pathogens when other laboratories are unable to do so. One such
laboratory, at the Division of Vector-Borne Infectious Diseases in Fort
Collins, Colorado, deals with viral and bacterial diseases transmitted by
vectors such as mosquitoes and ticks. It is part of CDC's National Center
for Infectious Diseases. Besides providing laboratory services, this
division also develops ways to diagnose vector-borne pathogens more quickly
and helps develop and evaluate approaches to preventing and controlling
outbreaks.
CDC is also the lead agency in HHS for bioterrorism preparedness. In recent
years, the President and Congress have been increasingly concerned about the
threat of terrorists using weapons of mass destruction, including biological
agents.1 Part of CDC's National Center for Infectious Diseases, the
Bioterrorism Preparedness and Response Program is responsible for public
health preparedness for potential acts of bioterrorism. In fiscal year 2000,
HHS received $278 million of the $10.2 billion in counterterrorism monies
allocated to federal agencies. Of the HHS funding, CDC received
approximately $155 million for bioterrorism preparedness programs in fiscal
year 2000, approximately $40 million of which is to be awarded to state and
local health departments for surveillance, epidemiology, laboratory, and
communications.
During the first recognized outbreak of West Nile virus in the United
States, infection of animals preceded the first human cases by at least 1 to
2 months. Large numbers of dying birds and an unusual cluster of human cases
were at first viewed as separate events. Gradually, as an increasing number
of laboratories became involved to conduct further testing on human, animal,
and mosquito samples, the linkages became clear, resulting in the
identification of the West Nile virus (see fig. 2). The scale of these
efforts was substantial, involving participants around the country. Since
the end of the outbreak, various local, state, and federal agencies have
taken actions to address the potential ongoing consequences of the virus's
introduction into North America.
The identification of a newly emerging infectious disease2 within a few
months was due to the combined, considerable efforts of scores of
individuals and several agencies in the animal and the human public health
fields and in academia. Here is an overview of the key events that occurred.
Appendix II contains a more detailed chronology.
The Animal Outbreak
No one is sure exactly when or how birds became infected. By late June a
veterinarian at an animal health clinic in the New York City borough of
Queens had examined and treated several birds that appeared to have nervous
system disorders, releasing those that survived. Reports of dead birds
increased through July and into August. By mid-August, dead birds were being
sent to the wildlife pathologist at the New York State Department of
Environmental Conservation. The wildlife pathologist was able to determine
that the birds were not dying from any of several common problems, but he
could not identify a clear cause. By late August, veterinarians at the Bronx
and Queens zoos had joined the effort to identify the disease, after several
wild and caged birds died on zoo property.
The Human Outbreak
Meanwhile, near the end of August, a specialist in infectious diseases in a
community hospital in Queens noticed that the hospital had an abnormally
large number of suspected cases of encephalitis or meningitis (diseases
involving inflammation of the brain or spinal cord) and that several of the
patients had developed an unusual pattern of muscle weakness. When the
hospital's doctors were unable to find a clear cause or an effective
treatment, the specialist called the Bureau of Communicable Disease within
the New York City Department of Health.3 After a quick but careful
investigation, city health officials contacted the state health department
and CDC for additional help. Blood and spinal fluid specimens from hospital
patients were rapidly tested at state and CDC laboratories. On September 3,
CDC announced that the test results were positive for St. Louis
encephalitis, a virus known in the United States but never before known to
occur in New York City. That same day, the city, assisted by the state and
CDC, launched a massive campaign to prevent people from being bitten by
mosquitoes and to determine the extent of the St. Louis encephalitis
outbreak.
Within the next week, however, the State Department of Health obtained what
appeared to be conflicting test results for St. Louis encephalitis, raising
doubts among some health officials about whether the exact cause of the
outbreak in humans had been determined. In addition, CDC officials were
questioned by city and state health workers and the public as to whether the
deaths of large numbers of birds and the human encephalitis cases might be
connected. Because St. Louis encephalitis had not been known to kill its
bird hosts, CDC officials said they considered the two outbreaks to be
unrelated. The cause of the outbreak in birds remained unidentified, and, to
help identify it, the zoo veterinarians and the state wildlife pathologist
enlisted the help of federal veterinary laboratories at the U.S. Department
of Agriculture (USDA) and the U.S. Geological Survey (USGS). By
mid-September, both laboratories concluded that the bird disease was caused
by a virus, that it did not appear to be any strain of St. Louis
encephalitis or other avian virus they had previously tested, and that they
had insufficient laboratory capabilities to identify it more specifically.
The USDA veterinary laboratory sent its virus samples to the CDC laboratory
for further analysis.
The Two Responses Converge and More Laboratories Become Involved
The test results in birds, along with repeated negative test results in
human samples in the state health department laboratory, increased the
doubts of some state health officials about whether the human disease agent
had been correctly identified as St. Louis encephalitis. On September 15,
they invited a visiting academic researcher from California to try out some
new testing methods on tissue specimens from human patients. The following
week, a Connecticut agricultural laboratory involved in that state's routine
mosquito surveillance reported isolating St. Louis encephalitis virus from
both a dead bird and mosquitoes collected near the outbreak area. This
finding was significant in implying that, if the virus was St. Louis
encephalitis, it was killing birds and possibly could be connected to the
human outbreak.
At about the same time, CDC had begun testing and retesting mosquito, bird,
and human specimens against a wider variety of flaviviruses in order to rule
out the possibility of another closely related virus. Independently, the
head pathologist at the Bronx Zoo gained agreement from the U.S. Army
Medical Research Institute of Infectious Diseases to attempt to identify the
virus in birds.
Beginning on September 23, the academic researcher and CDC came to the same
general conclusion: the virus causing the outbreak was not St. Louis
encephalitis but, rather, a virus that had never before appeared in the
United States. By the week of September 27, CDC had confirmed that a "West
Nile-like" virus was responsible for both the animal and the human
outbreaks.
The effort involved in addressing these outbreaks and identifying the cause
was concentrated and considerable. Hundreds of reported potential human
cases were investigated to determine whether West Nile was the infecting
virus. By the end of the investigation, health officials confirmed 62 cases
of West Nile virus, including 7 people who died. Thousands of bird deaths
were similarly investigated by several state and federal laboratories and
agencies, to determine how far the virus had spread. In addition to the
laboratory investigations, state and local emergency management teams were
mobilized to respond to public health concerns. They managed the
coordination of conference calls and other communications, the establishment
of hotlines to address the general public's concerns, and the procurement,
distribution, and application of pesticides. The New York City and State
Departments of Health also developed fact sheets for the public on each of
the pesticides in 1999, and in 2000 they implemented a surveillance system
for health effects from pesticides.4 Table 1 shows some specific examples of
the case surveillance and laboratory workload experienced by some of the
involved agencies during and since the outbreak. Not all of the agencies
involved have developed cost estimates for their efforts. As one indication
of the cost, however, New York State officials estimated that the state,
city, and four counties in the area spent more than $14 million on
protective measures such as mosquito control from late August through
October.
Agency Time frame Example of workload experienced
during and since the outbreak
Human case surveillance: The
city health department
investigated 622 suspect
hospitalized cases and 88
suspect outpatient cases that
were reported. Case
investigation included
contacting physicians and
hospitals, interviewing
patients, and coordinating
New York City Department of August to specimen collection and
Health, New York City December 1999 transport.
Animal and mosquito
surveillance: The city set up
and maintained mosquito traps,
established a hotline to
receive dead bird reports, and
triaged the collection of
specimens and submission for
testing to appropriate
laboratories.
Human case surveillance: The
state and local health
departments (outside of NYC)
investigated 229 suspect cases,
of which 196 were hospitalized.
Human sample testing workload:
Polymerase chain reaction (PCR)
tests for 13 viruses were
performed on 198 specimens from
190 patients.a Serology tests
were performed on almost 600
specimens. A laboratory
official indicated that before
New York State Health the outbreak, the average
Department (including number of requests for
counties outside of New York August to arbovirus tests was 40 to 50
City and New York State December 1999 per year.
Department of Agriculture
and Markets) Animal and mosquito
surveillanceb: As many as
17,000 dead birds were reported
by local health departments to
the state (one-third were
crows). The state health
department coordinated
submissions for testing, with
130 dead birds confirmed
positive (at federal
laboratories). Twenty-five
horse cases were reported. Over
25,000 mosquitoes (in more than
1,500 pools) were collected,
with 15 pools testing positive
(at CDC).
Avian sample preparation and
pathology investigations: The
department received,
New York Department of catalogued, and performed
Environmental Conservation, 1999 to necropsies (postmortem
Albany, N.Y. June 2000c examinations) on 880 dead birds
submitted from various parties
across the state; prepared and
mailed samples to various
laboratories for testing.
Human sample testing workload:
In 1999, CDC-Fort Collins
received over 1,200 samples
from New York alone for
testing, representing more than
CDC's Division of 700 patients. In past years,
Vector-Borne Infectious CDC has received 10 to 20
Diseases, 1999 specimens per year from the
state.
Fort Collins, Colo.
Avian sample testing workload:
CDC tested approximately 1,000
avian tissue samples and 3,000
serum samples from all
locations.
Avian sample testing workload:
The Center received almost
1,200 specimens from 22 states
and local jurisdictions,
including nearly 500 animal
carcasses for necropsy and
testing and 699 tissues for
testing for West Nile virus
from states such as New York
U.S. Geological Survey, and New Jersey.
National Wildlife Health Fall 1999 to
Center, Madison, Wisc. June 2000 Live bird surveillance: The
Center received almost 1,500
serum samples for West Nile
testing from collaborative
surveillance activities with
USDA in 10 states and from zoos
and endangered species in
captivity. Collected over 1,000
blood samples from wild birds
in New York City in October
1999 for expanded surveillance.
USDA National Veterinary Animal sample testing workload:
Services Laboratories, Ames, Fall 1999 to The laboratory performed almost
Iowa July 2000 120 virus isolation attempts
and 640 serum sample tests.
Note: Several other state and private agencies experienced significant
workloads. These examples represent New York City and State as well as
federal government activities.
aPCR is a laboratory process in which a particular ribonucleic acid (RNA) or
deoxyribonucleic acid (DNA) segment is rapidly replicated, producing a
large, readily analyzed sample of a piece of RNA or DNA.
bIn addition to laboratory testing, a large number of staff are involved for
surveillance and control and to respond to public inquiries, set up mosquito
traps, collect birds and mosquitoes for shipment, collect blood samples from
horses, establish computerized databases, complete specimen and summary
reports, prepare public information and maps, organize prevention and
response programs, and so forth.
cSpecimens from almost 20 crows stored in 1998 were sent for West Nile
testing in the fall of 1999.
Initial Outbreak
While the first frost of the season signaled the end to the initial outbreak
in 1999, activities at the national, state, and local levels have continued.
In the first week of October 1999 the New York City Department of Health and
CDC conducted a random survey of Queens residents to assess the overall
infection rate associated with the outbreak. The results of this serosurvey
(in which a blood test for West Nile antibodies is performed) revealed that
between 1.2 and 4.1 percent of the population in the area surveyed had been
infected with West Nile virus.
The change in diagnosis from St. Louis encephalitis to West Nile also caused
public health agencies to evaluate whether aspects of their intervention
response should be changed. While the West Nile and St. Louis encephalitis
viruses are closely related and mosquito-borne, the change in diagnosis had
some implications for the intervention approach. For example, past research
had shown that different types of mosquitoes might carry the viruses. Both
West Nile and St. Louis encephalitis are carried by a certain species of
mosquito, Culex pipiens. However, West Nile is also carried by other
species, including Aedes vexans and Anopheles. Some of these species have
different habitat and activity patterns. For example, Culex pipiens breeds
in polluted water and is active at night, while A. vexans has been found in
natural areas and is active during the day.5 Once the distinction between
the viruses was made, the public health interventions were changed
accordingly to reflect the other types of mosquitoes potentially carrying
the West Nile. For example, local public health notices stated that the
public should also avoid contact with mosquitoes active during the day.
While these differences are not considered significant since the public
health recommendations for mosquito control are appropriate in either case,
they illustrate the potential significance of an accurate diagnosis in that
even closely related viruses might require different responses.
Some of the activity since the initial outbreak has involved learning more
about where the virus came from and when it arrived. Research into the
origins of the virus found that it is most closely related to a strain
isolated in a goose found in Israel in 1998. Testing of previously stored
bird tissue samples at the Bronx Zoo was negative for West Nile virus,
suggesting the virus was introduced in 1999.
Much of the ongoing effort has been applied to determining whether West Nile
will be an ongoing threat to animal and human health. The West Nile outbreak
represents a potential problem stretching well beyond New York City, because
the virus can spread through bird migrations. In fiscal year 2000, HHS and
CDC will provide approximately $10 million for West Nile virus activities.
This amount includes grants totaling $4.5 million available to 19 state and
local health departments6 along the Atlantic flyway of migratory birds for
West Nile virus surveillance in humans, mosquitoes, and birds. An additional
$2.7 million of the $10 million has been made available to 31 other state
health departments to expand surveillance capabilities. As of August 2000,
communities in at least seven eastern states7 had undertaken active mosquito
control programs, such as spraying, as well as public education campaigns
and surveillance activities.
Surveillance activities have already produced evidence that West Nile has
spread to other areas. In October 1999 a dead crow carrying the virus was
found in Baltimore, Maryland. In 2000, as of August, West Nile virus had
been detected in birds in nearly all New York counties as well as in
Massachusetts, Connecticut, Rhode Island, and New Jersey and in mosquito
pools in several states. If West Nile is carried further south along bird
migratory routes (see fig. 3 for examples), it could become permanently
established in the Western Hemisphere.
West Nile
Source: New Scientist, http://www.newscientist.com/nl/0708/birds.html.
The spread of the virus by birds and mosquitoes has significant implications
for animal health as well. Animal health officials are concerned about the
potential effects on wildlife and other animals, particularly those birds
that are susceptible to fatal illness from the virus. The USGS, which
conducts surveillance of wildlife health, has helped develop and maintain
national maps showing the current wildlife surveillance data now submitted
by states.8 Economic concerns also have been raised. While wild birds were
the primary carrier of West Nile in last year's outbreak, the disease was
also detected in domestic livestock. Twenty-five cases were identified in
horses on Long Island, nine of which died or were euthanized. Although there
is no evidence that the virus can spread from infected horses to uninfected
horses or other animals, countries from Argentina to the United Arab
Emirates placed import restrictions on horses from affected areas.9 In
addition, the role of commercial poultry in maintaining or transmitting the
virus is not thoroughly understood. CDC research has found that chickens can
develop a short-lived infection without clinical signs.10
Several organizations, including CDC, USDA, the Wildlife Conservation
Society, and Flushing Hospital, have organized conferences and workshops to
review the West Nile virus outbreak. In December 1999, CDC issued guidelines
for West Nile virus surveillance, prevention, and control. In the spring of
2000, HHS and USDA appointed West Nile coordinators to oversee efforts
against the virus. See appendix III for a list of some key publications
about or related to the virus outbreak.
While many officials and experts we contacted believe aspects of the
outbreak investigation went quickly and well, nearly all of them also
believe there were lessons to be learned. These lessons may be especially
relevant for acts of bioterrorism, where the outbreak of cases may be much
more rapid and law enforcement agencies may need to be involved to prevent
terrorists from releasing additional biological agents. The time available
for decision-making and response may be compressed from days or weeks to a
matter of hours. The lessons we identified related primarily to addressing
possible needs in five areas:
� local surveillance and response capabilities,
� communication among public health agencies,
� coordination between public health and animal health efforts,
� capabilities of laboratories, and
� efforts to distinguish between natural and unnatural events.
The West Nile outbreak provided a number of lessons about surveillance. We
learned that many aspects of the surveillance network worked well, speeding
the response to the outbreak. These positive lessons can serve as models for
other communities that may have less substantial surveillance networks.
However, while several of the lessons are positive, the outbreak also
exposed some weaknesses.
Many Aspects of Surveillance and Response Worked Quickly and Well
The human outbreak of West Nile began with a few unusual cases. The
potential that one or two persons' medical conditions could be an indication
of some larger concern, such as an emerging infectious disease, may not be
readily apparent to the health professionals involved. In many cases, such
events might not be noticed until a number of physicians have reported the
cases and the local health department identifies a cluster, or a number of
victims seek care for similar conditions at the same location. Alert
responses by the doctors and nurses who first see such victims are
particularly crucial in alerting the public health community to the
possibility of a wider problem.
In the West Nile outbreak, several actions were particularly important in
providing this early alert, as well as in providing valuable evidence for
the investigation. Among these actions are the following:
� The physician who encountered the first human cases at the local hospital
in Queens reported the unusual cluster of illnesses to local public health
officials. Such occurrences could easily go unreported, if, for example, the
physician does not consider the circumstances to be unusual enough to report
or does not recognize a rare disease.
� Epidemiologists and staff at the New York City Department of Health took a
number of actions that were essential to containing the outbreak. They
quickly investigated and recognized the potential significance of the
initial case reports. Their interviews with patients and families identified
common features in how the patients were exposed out of doors, suggesting
that a mosquito-borne disease might be involved. They canvassed all New York
City area hospitals to identify potential cases, and throughout their
investigation, they remained in daily touch with the many local, state, and
federal officials who had quickly become involved. These staff members said
previous planning for bioterrorism response in place at the city health
department was key to the success of the Department's response.11
� Autopsies were performed on the victims. The New York City Department of
Health and Office of Chief Medical Examiner worked together to ensure that
autopsies were performed on any fatal case of encephalitis. Autopsies were
performed on over 25 fatal cases who were initially suspected as having
viral encephalitis, including all 4 fatal cases of West Nile encephalitis
that occurred among city residents. According to one assessment of the
response, information obtained from the autopsies pointed to a flavivirus as
the cause and helped guide subsequent laboratory testing.12 Autopsy rates
nationally have been decreasing, at a time when public health officials
believe they should increase to help detect infectious diseases. The decline
has been influenced by such factors as costs and jurisdictional and
authorization uncertainties.
While the West Nile outbreak was identified more quickly than otherwise
might have been expected because an astute physician reported two unusual
cases, it still provides evidence that the reporting system could be
improved. The virus might have been identified earlier--perhaps by a week
according to an involved official--if case reporting had been better and if
good baseline data showing past trends of encephalitis and related diseases
had been available. Similarly, a physician we interviewed who had treated
West Nile patients said clinicians often do not know whom to call when a
cluster of patients with a disease of unknown origin is noticed. Wildlife
and zoo officials also indicated that within their fields there is a need
for better information and guidance about whom to contact in the public
health community when an outbreak is suspected.
These problems have been noted in other instances besides the West Nile
outbreak. For example, a November 1998 workshop on public health systems and
emerging infections sponsored by the Institute of Medicine--an organization
chartered by the National Academy of Sciences to examine public health
policy matters--reported that physicians are not sure when or where to
report suspicious cases of infection. The workshop also reported that
physicians are unaware of the need to collect and forward clinical specimens
for laboratory analysis and may not be educated regarding the criteria used
to launch a public health investigation. Unlike the case in New York City,
where the health department had been actively communicating with physicians,
the workshop found that there is often a lack of communication between
public health agencies and community physicians.13
A 1999 assessment by the Institute found that disease surveillance systems
in place at local, state, and federal levels rely on systems of disease
reporting from health providers that are notorious for their poor
sensitivity, lack of timeliness, and minimal coverage.14 Because an
effective medical response to a bioterrorist event would depend in part on
the ability of individual clinicians to identify, accurately diagnose, and
effectively treat diseases (including many that may be uncommon), the
Institute reported that education about the threat posed by bioterrorism and
about the diagnosis and treatment of various agents deserves priority.
Some Inadequacies in Resources for Surveillance Were Exposed
Although this outbreak was relatively small in terms of the number of human
cases, it taxed the resources of one of the nation's largest local health
departments. The strain on resources is particularly noteworthy because
local health departments in the United States have initiated nearly all the
investigations that led to the recognition of infectious disease outbreaks.
At the time of the West Nile outbreak, the New York City Department of
Health had a unit of about eight people responsible for surveillance and
case investigations related to over 50 reportable infectious diseases.
Officials told us that having even this small number of trained staff
available was critical to the quick response to the initial outbreak. Once
the outbreak was identified, these and other staff assigned to help from
other agencies and departments worked long hours, seven days a week.
We reported in 1999 that surveillance for important emerging infectious
diseases is not comprehensive in all states, leaving gaps in the nation's
surveillance network.15 Many state epidemiologists reported inadequate
staffing for generating and using laboratory data--often considered more
reliable for case investigation purposes than physician-reported data--for
performing infectious disease surveillance. The Institute of Medicine
workshop reported that, in general, epidemiological investigations and
surveillance efforts are challenged by a variety of factors. These include
changes in the health care system and the continuing use of paper-based
disease-reporting systems in many locations, where surveillance is
consequently sporadic and inadequate.16
Experts consider rapid and reliable communication among public health
agencies to be essential to bioterrorism preparedness and coordination.
Timely dissemination of information allows public health officials to make
decisions with the most current information available. During the West Nile
outbreak, however, officials indicated that the lack of leadership in the
initial stages of the outbreak and the lack of sufficient and secure
channels for communication among the large number of agencies involved
prevented them from sharing information efficiently.
Many officials interviewed pointed to the lack of clear reporting guidelines
as one source of confusion. Knowing who was in charge or could act as an
agency spokesperson, and which agency was responsible for what, would have
allowed each agency to operate more effectively. Some officials suggested
that each agency should have one "point person" overseeing operations and
the flow of information.
During the outbreak, local, state, and federal officials held daily
conference calls coordinated by the City or State Department of Health, or
CDC. During these calls, officials received up-to-date information on such
topics as the human and animal surveillance systems, test results from each
laboratory, and schedules for mosquito spraying. While these calls were
considered necessary to ensure that all parties heard the same information,
they sometimes involved over 100 people and lasted 2 hours or more.17 As a
result, key officials had less time to investigate the outbreak in the
laboratory and in the field. Additionally, veterinary health officials were
concerned because they were not always included in these calls.
While a secure electronic communication network was in place at the time of
the initial outbreak, not all involved agencies and officials were using it
at the time. For example, because CDC's laboratory was not linked to the New
York State network, the New York State Department of Health had to act as an
intermediary in sharing CDC's laboratory test results with local health
departments. CDC and the New York State Department of Health laboratory
databases were not linked to the database in New York City, and laboratory
results consequently had to be manually entered there. Physicians, local
health departments, and laboratory officials indicated that during the
outbreak, it was sometimes difficult to determine the status of patients'
samples and of the laboratory results. During and since the outbreak,
however, officials indicated that the use and utility of the network have
improved for West Nile surveillance and information sharing. Using the
network, the state has put together an interactive surveillance system for
mosquito, bird, and human disease reports. Since the fall of 1999, access to
the network has been provided to more health officials, including animal
health agencies, for tracking West Nile in animals and humans. The
communication limitations during the outbreak, the resulting changes to the
electronic network capabilities, and the increased reliance on the network
for sharing information have increased awareness of the need for established
electronic data-sharing mechanisms.
New York State officials told us that the state has invested heavily in its
communication infrastructure and has created an advanced information system,
but at a national level some local health departments still do not have
access to modern communication technologies. A 1999 survey by the National
Association of County and City Health Officials found that one-third of
health departments serving fewer than 25,000 people did not have access to
the Internet or electronic mail. Similarly, more than half the agencies
surveyed had neither continuous, high-speed access to the Internet nor
broadcast facsimile transmission capabilities.
Important
The West Nile events illustrate the value of communication between public
and animal health communities, the latter including those dealing with
domestic animals, wildlife, and other animals such as zoo animals. Many
infectious diseases, including West Nile, are zoonotic, that is, capable of
infecting both animals and people. According to recent research,
approximately three of every four emerging infectious diseases reach humans
through animals.18 Of over 1,700 known pathogens affecting humans, including
viruses and bacteria, 49 percent are zoonotic. Of the 156 pathogens
associated with emerging diseases, 73 percent are zoonotic. Many of the
viruses or other pathogens considered most likely by CDC to be used in a
bioterrorist incident are zoonotic, such as anthrax, plague, brucellosis,
tularemia, and the equine encephalitic viruses. An official of the USGS
National Wildlife Center noted that many zoonotic pathogens become
established in wildlife before they are transmitted to humans and domestic
animals. The November 1998 Institute of Medicine workshop reported that,
because of their familiarity with a number of these biological agents, the
veterinary medicine community should not be overlooked in surveillance
efforts.19 Moreover, veterinarians and veterinary laboratory workers are
likely to have been vaccinated against many zoonotic diseases and are used
to working with zoonotic pathogens.
The West Nile outbreak shows how domestic, wild, and zoo animals can be
considered "sentinels," providing an early warning device for diseases that
can harm people. Even for a deliberate biological attack, animals may be the
first victims, unintentionally or as part of an effort to avoid discovery,
according to the Institute of Medicine and National Research Council.20 In
the case of the West Nile outbreak, USDA and USGS National Wildlife Center
laboratories were involved in early or mid-September in testing bird samples
prior to the identification of the West Nile virus. However, because these
laboratories lacked reagents21 for the virus, they were unable at the time
to specifically identify it.
Experience with the West Nile outbreak also illustrates how links between
the animal and public health communities were missing. For example,
� Some key public health officials, such as the city health department's
Director of the Bureau of Communicable Disease, indicated that they were not
aware of the similarities in the clinical symptoms occurring in the birds
and humans until many days or weeks after the human outbreak began.
Officials said they believe that communication was hindered even further
because, even within the animal health community, there is fragmentation at
the state and federal level in what agencies are responsible for different
types of animals. For example, domestic animals, such as cats and dogs, are
usually the responsibility of state and local health departments. Livestock,
such as cattle and swine, are often the responsibility of state agricultural
agencies. Wildlife, such as birds, are under the state environmental or
wildlife agencies.
� When wildlife health officials approached the state public health
laboratory to test the bird samples, they were told their samples should be
tested at another laboratory, because the state laboratory did not have the
reagents to perform animal (bird) testing. According to a New York State
animal health official, not having adequate capacity within the state
laboratory to test animal samples can create administrative and cost
barriers to getting samples tested. For example, many veterinary
laboratories will test samples only on a fee basis and not for public health
purposes. In some areas of the country, such as the Southwest, where
zoonotic diseases such as hantavirus are endemic in the animal population,
integration of the animal and public health communities is considered to be
better.
� Several persons involved in the outbreak commented that the zoo community
is currently left out of the animal and public health paradigm, even though
zoo animals may be useful sentinels. Zoo animals generally receive close
attention from veterinarians, and in some cases pathologists track health
care and disease causes, creating detailed health records and storing tissue
samples for future analysis. Officials indicated that because zoo animals
are not considered to be wildlife or domestic animals, they do not fall
within the jurisdiction of animal health agencies such as the USGS, which
tracks wildlife issues, or the USDA, which tracks concerns related to
domestic animals. The Bronx Zoo pathologist tried many different channels in
order to find laboratories willing to prioritize performing additional tests
on the bird samples and to provide advice on needed safety precautions for
zoo laboratory personnel working with the bird samples.22
Many officials provided other examples of where communication between public
and animal health communities had not worked well and indicated that the
West Nile events pointed to a need for better partnership between these
communities. This opinion was voiced even by those who at first disregarded
animal health officials' views and questions about the potential links
between the animal and the human outbreaks. For example, in its own internal
assessment of the West Nile events, CDC concluded that the relationships
between public health agencies at the federal, state, and local levels and
their counterparts in public and private agencies that monitor veterinary
health should be strengthened. There are indications that some of this
greater collaboration has begun. Since the outbreak, archived blood samples
from zoo animals drawn in past years have been analyzed as part
of the ongoing investigation to determine when and how West Nile was
introduced.23
Laboratories Are Needed
Another frequently cited lesson was the need for improved laboratory
infrastructure and technologies for responding to outbreaks and newly
emerging viruses. While the concerns were wide-ranging, three common themes
emerged: broadening laboratory capabilities, ensuring adequate staffing and
expertise, and improving ability to deal with work surges in testing needs.
Since the extent to which public health and other laboratories across the
country are capable of safely testing dangerous pathogens is unknown, a
first step in addressing these concerns may be to complete assessments of
inventory and core capacity needs. At the same time, lessons from the West
Nile outbreak point to the need to improve current linkages among
laboratories.
Broadening Laboratory Capabilities
The need for enhanced laboratory capabilities was frequently mentioned by
officials involved in the West Nile outbreak, as well as in various
assessments. Officials pointed out the need for more laboratory capacity for
identifying and handling infectious agents of high concern to human health,
particularly emerging or exotic ones. For example, they said that at the
time of the outbreak, only two or three laboratories in the country had the
reagents necessary to identify the West Nile virus. One of these was CDC's
laboratory in Fort Collins, which did not initially use this reagent since
the first test it had performed was consistent with the related St. Louis
encephalitis virus.24 Because New York State's laboratory was considered
less equipped to perform the diagnostic testing on the human samples once
the outbreak was identified, CDC performed the bulk of these tests. In this
regard, the need to "expect the unexpected," a phrase frequently quoted in
outbreak assessments, expresses the importance of developing a broader
awareness within the laboratories of the potential for new agents to appear
and, concurrent with such awareness, developing broader testing capacity.
One federal laboratory official suggested, for example, that federal policy
should consider a broader dissemination of methods for identifying more
exotic pathogens--perhaps those pathogens that are more likely to be
introduced to the country through international travel or otherwise.
Some bioterrorism and public health officials noted that, while expansion of
laboratory capacity is vital to preparedness, efforts to identify more
exotic agents may be beyond the scope of all but the largest health
departments and therefore should be a regional or state-based activity.
Consequently, some experts have suggested research into determining the
utility of developing a network of regional laboratories capable of rapid
diagnostic testing.25 Determining current capacity will be a key first step
in assessing the need for a regional network. Currently, the number of
public health and other laboratories that can handle those viruses
considered most harmful (those classified as requiring Biosafety Level-3 or
Biosafety Level-4 equipment, trained staff, and safety procedures in place)
is unknown.26 CDC information indicates that most states lack the public
health laboratory capacity to handle many of those viruses that CDC has
classified as dangerous and identified as high priority because of risk to
national security and public health. Specifically, in fiscal year 1999, less
than half of the over 40 states and localities receiving funding for
laboratory capacity through CDC's bioterrorism preparedness grant program
reported having advanced capacity for rapid testing for at least four
critical biologic agents.27 Within the veterinary community, a USDA official
told us that probably fewer than 20 veterinary laboratories across the
country have the capacity to test for Biosafety Level-3 pathogens, and no
veterinary laboratories have Biosafety Level-4 capacity.28
Ensuring Adequate Staffing and Expertise
Several officials commented on the declining capacity and expertise within
the federal and state public health laboratory infrastructure, particularly
as it relates to zoonotic and vector-borne diseases. At the time of the
outbreak the Fort Collins laboratory capacity was considered to be low, and
many needed specialist positions had been eliminated or left vacant as
experienced staff had left. Similarly, CDC reported that only a few states
and even fewer local health departments have trained personnel or the
resources to adequately address vector-borne diseases. According to CDC and
other officials, the infrastructure of laboratories with the capacity to
handle such diseases has deteriorated in recent decades. The number of
laboratories and extent of capacity have dropped, and the staffing, physical
plant, and financial support of many remaining laboratories have also been
affected.
New York State, prior to the outbreak, lacked the capacity to address
vector-borne diseases. A New York State laboratory official indicated that
at one time the state had 5 or 6 staff to perform mosquito surveillance to
track viruses. In recent years the laboratory's staff had been cut back as
funding was diverted to other public health priorities. By contrast,
Connecticut officials indicated that they had--after a similar encounter
with eastern equine encephalitis, another mosquito-borne virus--instituted
mosquito surveillance in 1997, at a cost of about $200,000.29 Because of its
ongoing surveillance program, the state was able to quickly respond to the
outbreak, placing mosquito-monitoring devices in potentially infected areas
and identifying the appropriate places to spray. According to a program
official, having baseline data--for example, data on where most mosquitoes
of concern resided in previous years--allowed the state to make informed
decisions about where to spray.
Improving Ability to Deal With Surges in Testing Needs
Testing for West Nile taxed those parts of the laboratory system that were
dealing with the outbreak--and in some ways, affected what some of these
laboratories were normally expected to do. The New York laboratory that was
testing samples for St. Louis encephalitis was also dealing with an outbreak
of Escherichia coli O157:H7 at the same time.30 Both the New York State and
CDC Division of Vector-Borne Infectious Disease laboratories were quickly
inundated with requests for tests, and because of the limited capacity at
the New York laboratories, the CDC laboratory handled the bulk of the
testing. CDC officials reported that nearly all the Fort Collins Arbovirus
Disease Branch laboratory staff at one point was working on the response to
the virus. Normally, the CDC laboratory functions as a reference laboratory
for arboviruses, maintaining the technology and capability to accurately
diagnose viruses of this type.31 In this case, it was acting largely as a
diagnostic laboratory, testing patient samples to determine who had the
virus and who did not. Officials indicated that the CDC laboratory would
have been unable to respond to another outbreak, had one occurred at the
same time. Some officials also described what were considered to be
unfortunate aspects of CDC's taking on the role of the diagnostic
laboratory. Typically, the CDC laboratory's role would be to confirm test
results rather than to perform diagnostic testing. In this case, in
assisting the state in performing the diagnostic testing, CDC focused on
determining whether individual patients had St. Louis encephalitis (and then
West Nile) rather than identifying other possible causes of illness. This
was considered by some to be unfortunate from the standpoint of the
individual patients, whose diagnoses could therefore be delayed. Testing at
the state laboratory from 95 patients with suspect viral infections found
16, or about 17 percent, of the patients positive for viruses other than
West Nile.
Improving the laboratory network is key to improving the laboratory capacity
to respond to surges in workload and to provide the new technologies, staff,
and expertise to respond to outbreaks. Networks or linkages among federal,
state, academic, and possibly private sector laboratories may also be
needed, in part to clarify responsibilities for involved laboratories for
providing surge capacity, diagnostic testing, and other critical roles in
emergency situations. CDC's internal investigation concluded that the agency
should enlist help from academic laboratories. The California researcher who
conducted some of the diagnostic laboratory work on the West Nile outbreak
was brought in by officials at New York State's Department of Health because
they learned of the innovative research his laboratory was developing to
quickly and accurately identify the viral causes of unexplained deaths from
encephalitis.32 Some involved officials indicated that the California
laboratory's involvement was fortuitous in allowing a laboratory not
consumed with diagnostic testing for the outbreak to focus on performing the
types of tests required to eventually identify the virus. On the other hand,
some officials also indicated that this laboratory's unplanned involvement
contributed to confusion about which laboratories were performing tests and
the types of tests being performed.
Those involved in responding to the West Nile outbreak have concluded that
with a more formal network and clearer roles,
� necessary tests to accurately identify the virus could have been started
sooner, and
� the resulting confusion about which federal and other laboratories were
involved in the process and the tests each laboratory was performing could
have been avoided or minimized.
However, while many agree that more should be done to develop the laboratory
network, the plans for such a network are still being developed. CDC's
planned laboratory response network for bioterrorism--linking public health
laboratories at the local, state, and federal levels--is still under
development.33 Private, veterinary, and USDA laboratories are not yet part
of the network.
Assessment of the public health infrastructure by public health experts, and
CDC's strategic plan for preventing emerging infectious diseases, also point
out the need for defining and building the laboratory network. The Institute
of Medicine workshop that assessed the capabilities of the public and
private sectors for identifying emerging infections reported that surge
capacity in response to an outbreak is an area in which the public health
laboratory should define its core capability and standards, including the
unique and complementary roles of the public and private sector
laboratories.34 CDC's strategic plan has a goal to strengthen the public
health infrastructure in part by strengthening CDC's capacity to serve as
the national and international reference laboratory for the diagnosis of
infectious diseases.35
Show Common Elements of Preparedness
Finally, the outbreak and surrounding events illustrate the challenges
inherent in recognizing a bioterrorist event versus a natural outbreak. In
October 1999 a media report suggested that the outbreak could have had an
unnatural origin.36 The Central Intelligence Agency examined the allegations
and concluded that there was no evidence indicating that the outbreak was
caused intentionally.
The report of the possibility of a bioterrorist event, and the difficulties
in correctly identifying the virus and its source, highlight how hard it can
be to determine whether an outbreak has an unnatural origin. While the
actual response to the West Nile virus outbreak might not have been
significantly different had it been considered a potential bioterrorist act,
such an event would require the involvement of additional organizations to
carry out a criminal investigation. CDC's current recommended protocols are
to notify the Federal Bureau of Investigation and law enforcement officials,
who would also seek to determine whether terrorists had targeted additional
locations for release of the pathogen. The need to involve these agencies
may not be evident at the start. An HHS Office of Emergency Preparedness
official indicated that an investigation of a real bioterrorism attack may
start as an emerging infectious disease outbreak investigation that finds
that the cause was terrorism. It is difficult to establish specific criteria
for reporting an outbreak as suspicious, but officials indicated that
improved reporting criteria may be needed.
The West Nile investigation is not the only incident that has illustrated
the difficulties of determining whether an outbreak was intentionally
caused. According to the Federal Bureau of Investigation, there has been
only one act of terrorism in the United States in which a biological agent
was used, and in this case the deliberate cause was not known until long
after the outbreak had passed. The event occurred in September 1984, when
751 persons in Oregon became ill with gastroenteritis, an inflammation of
the stomach and intestines. The local health department, with assistance
from CDC, discovered that food at salad bars had been contaminated with
Salmonella typhimurium. More than a year later, the Federal Bureau of
Investigation learned through a former member of a religious cult that the
cult had used the Salmonella to contaminate the food.37
The West Nile outbreak may also illustrate the importance of improving our
understanding of the causes of unexplained deaths of previously healthy
people. Currently, much is unknown about the specific pathogens that cause
the deaths of Americans from suspected infectious diseases. Most of the
specific causes of encephalitis are undiagnosed. From the point of view of
improving surveillance for acts of bioterrorism, a key may be in improving
the ability to identify the causative agent in any case where the disease is
serious and unusual. One effort toward this end is CDC's unexplained death
project. The project--the focus of the Albany conference at which the
academic laboratory at the University of California at Irvine was asked to
use innovative techniques to test the human samples--aims to improve CDC's
capacity to rapidly identify the cause of unexplained deaths or critical
illness, and to improve understanding of the causes of specific infectious
disease syndromes for which a cause is often not found.38
Finally, the outbreak and surrounding events support public health
officials' views that bioterrorism preparedness rests in large part on the
soundness and preparedness of the public health infrastructure for detecting
any disease and the causes of disease outbreaks. An important public health
responsibility in any disease outbreak is to identify the agent and source
of the disease as part of the process to determine how to prevent it from
spreading further. From the public health standpoint, whether an outbreak is
natural or artificial may be of little significance, although the political
or legal ramifications may be large.39 Bioterrorism preparedness officials
aware of the West Nile outbreak and investigation indicated that because the
local public health officials were taking appropriate steps to identify the
spread and source of the disease, the proper steps were under way for
determining whether the source or origin should be considered suspicious.
Appendix III contains a bibliography of selected assessments and reports
that relate to the public health infrastructure and bioterrorism
preparedness.
The sudden appearance of West Nile virus in this hemisphere is a clear
illustration of the often-repeated need to "expect the unexpected." Much of
the initial response was based on typical steps for identifying and
responding to diseases that occasionally break out in the United States.
From that standpoint, the correct public health agencies were involved and
the response was timely and appropriate. But in this case, critical
information and clues pointing to a newly emerging virus were discounted
early on, but reemerged later. Persistence, coupled with the significant
contributions of additional laboratories, investigators, and researchers,
produced the additional evidence leading to the final identification of West
Nile as the cause of the outbreak. However, as more agencies became
involved, coordination with those already involved in the investigation was
not always effective, and communication became more difficult.
How can this incident be translated into increasing the likelihood that the
public health network can detect similar threats and then identify and
contain them more effectively in the future? The public health community is
doing a great deal to respond--both to this particular outbreak, which
continues to unfold, and to the larger set of concerns it raised. The
lessons we identified are, to some extent, already part of that ongoing
effort.
These lessons support the view of many that "an outbreak is an outbreak is
an outbreak"--that is, whether an outbreak is intentional or natural, the
public health response of determining the causes and containing its spread
will be the same. Thus, policies and actions that improve the capabilities
of the public health infrastructure--including those that improve the animal
health infrastructure--do more than help the nation better prepare for a
potential bioterrorist event. These same improvements will also increase our
ability to detect and contain the more likely sort of outbreak that starts
with a global traveler, a wayward mosquito, or a migrating bird.
We provided a copy of the draft report to CDC, USDA, and New York City and
State Department of Health officials for comment. CDC and the New York City
Department of Health provided written comments, which are provided in
Appendices IV and V. USDA and the New York State Department of Health also
provided comments, which are summarized below.
Generally, officials agreed with the lessons and conclusions drawn from
experience that are presented in the report. The commenting agencies also
offered several observations on various aspects of the report draft. CDC
said that its strategic plans for emerging infectious diseases and
bioterrorism should be mentioned in the report, and we have done so. CDC
expressed a concern with the emphasis in the draft on those aspects that did
not go as well as others. Because this report was designed to analyze the
events of the fall of 1999 and identify lessons learned for the nation's
preparedness, it necessarily focused on those things that were perceived as
problems at that time. CDC also expressed a concern that the report
overemphasized the role of the convergence of the human and animal
investigations, because laboratory tests conducted by the California
researcher and others on the human side were also showing that the virus was
not the one initially identified as the cause at the same time as the animal
tests. We agree that these contributions were significant, and we made
clarifications to the text to recognize them. Nonetheless, we continue to
believe that the information from the animal investigations was critical to
the timing of the final accurate diagnosis.
New York City Department of Health officials highlighted as important the
points in the draft discussing the importance of effective disease
surveillance, the need for better communication among public health
agencies, and particularly the need for better communication within and
among public and animal health communities.
USDA officials indicated that increased emphasis is warranted on the
importance not only of public health preparedness, but also of animal health
preparedness. Several New York State Department of Health officials and all
of the agencies mentioned above provided technical comments, which were
incorporated where appropriate.
We also provided relevant excerpts of the draft report to officials from the
Bronx Zoo, State of Connecticut, New York State Department of Environmental
Conservation, USGS, and University of California at Irvine for technical
review, and their comments were incorporated in the draft where appropriate.
We are sending copies of this letter to Donna E. Shalala, Secretary of
Health and Human Services; Daniel R. Glickman, Secretary of Agriculture;
Jeffrey Koplan, M.D., Director of CDC; and other interested officials.
This work was performed under the direction of Marcia Crosse, Assistant
Director. Other major contributors are Rob Ball, Katherine Iritani, Anita
Kay, Deborah Miller, and Stan Stenerson. Please contact me at (202) 512-7119
if you or your staff have any questions.
Sincerely yours,
Janet Heinrich
Associate Director, Health Financing
and Public Health Issues
Methodology
We interviewed officials in the public and private sectors at the national,
state, and local levels, and, to the extent it was made available to us, we
obtained relevant documentation from them. With this information, we
developed a chronology and compiled a list of lessons learned from the West
Nile virus outbreak. To some extent, the chronology was based on officials'
recollections of the specific events occurring on particular dates. When
information provided by agencies or officials was inconsistent, we assessed
its relevance to our reporting objectives, sought any needed corroboration
from other involved officials, and incorporated the information accordingly.
Officials and agencies contacted included the following:
� U.S. Department of Health and Human Services, Office of Emergency
Preparedness
� Centers for Disease Control and Prevention, National Center for Infectious
Diseases, Division of Vector-Borne Infectious Diseases, Division of Viral
and Rickettsial Diseases, Division of Bacterial and Mycotic Diseases
� Central Intelligence Agency
� U.S. Department of Agriculture, Animal and Plant Health Inspection Service
� U.S. Geological Survey, National Wildlife Health Center
� U.S. Army Medical Research Institute of Infectious Diseases
� New York State Department of Health
� New York State Department of Environmental Conservation
� New York City Department of Health
� New York City Commissioner's Office of Emergency Management
� Wildlife Conservation Society/Bronx Zoo
� Flushing Hospital Medical Center
� Connecticut Agricultural Experiment Station
� University of California at Irvine
� Association of Public Health Laboratories
� National Association of County and City Health Officials
� a ProMED moderator active during the initial outbreak
To gather background information and relevant literature on the West Nile
outbreak, West Nile virus, and surveillance activities put in place since
the outbreak, we searched academic journals and news media and performed an
extensive review of publications related to the virus. We performed a
similar review to identify reports and literature related to the
preparedness of the public health infrastructure for a bioterrorist event.
We also reviewed assessments of the response to the West Nile outbreak
prepared by various agencies. These assessments both describe the views of
these agencies on lessons learned and outline the steps they have taken and
policies they have implemented since the initial outbreak.
Timeline of Key Dates and Events in the West Nile Virus Outbreak, 1999
Time is of the essence in responding to an outbreak of an infectious
disease. When the cause of an outbreak is unknown, it is much more difficult
to respond quickly and effectively. As can be seen in the following
chronological table of events, the key to rapidly identifying and responding
to the West Nile virus outbreak lay in merging efforts and information from
separate investigations of outbreaks in animals and humans. At the same
time, as the number of participants increased, so did the complexity and
difficulty of communication and coordination. Looking back on the outbreak
of the fall of 1999 provides an opportunity not only to review the
significant investigative and laboratory work of a myriad of participants
and the contributions of each toward the final diagnosis of the virus, but
also to analyze the communications and actions of the responding government
agencies in order to improve the nation's preparedness for future outbreaks,
including ones not due to natural causes. Table 2 provides a detailed
chronology of significant actions and events.
Date Phase 1: Animal Outbreak Phase 2: Human Outbreak
(Approx. date) Connecticut
Tuesday, Agricultural Experiment
6/1/99 Station begins annual
mosquito surveillance.
(Approx. dates)
Veterinarian at Bayside
Mid-June to veterinary clinic finds
late July crows with signs of nervous
1999 system disorders, treats
birds, and releases those
that survive.
(Approx. date) New York
State (NYS) Department of
Environmental Conservation
investigates bird
poisonings in New York City
(NYC) parks, obtains many
reports and samples of dead
birds, especially crows.
Tuesday, 8/2/99: Earliest case of human
(Approx. date) Veterinarian infection with West Nile virus
8/1/99 to at Wildlife Conservation identified in retrospective
Center, Queens, treats study. Case was unreported and
Friday, several sick wild birds and unknown until after
8/13/99 releases those that identification of West Nile
survive; sends specimens to virus in late September.
NYS Department of
Environmental Conservation.
(Approx. date) Zookeeper at
Bronx Zoo tells zoo
veterinarians he has heard
reports about dead crows.
Queens branch of Wildlife
Conservation Society
reports dead wild birds to
the Bronx Zoo branch.
Flushing Hospital in Queens
admits an elderly patient who,
Thursday, after a few days, develops
8/12/99 Bronx Zoo branch of serious neurologic symptoms,
Wildlife Conservation including unusual pattern of
Society sends dead bird muscle weakness.
samples to wildlife
pathologist at NYS
Department of Environmental
Conservation.
(Approx. date) Nassau Flushing Hospital admits an
Sunday, County, N.Y., highway crew elderly patient with heart
8/15/99 brings in a bag of dead failure; after a few days he
crows to NYS Department of develops neurologic symptoms,
Environmental Conservation. including muscle weakness.
ProMED (Internet bulletin
board posting news of
infectious disease
Monday, outbreaks) posts news about
8/16/99 bird poisonings in NYC,
says NYS Department of
Environmental Conservation
is investigating.
(Approx. date) Wildlife
pathologist at NYS
Department of Environmental
Conservation performs
Tuesday, necropsies (postmortem
8/17/99 examinations, or autopsies)
of dead birds, examines for
aspergillosis (fungal
infection), poison,
bacteria.
Flushing Hospital admits another
Wednesday, elderly patient with symptoms
8/18/99 similar to those of the 8/12/99
admission.
Article in local Queens
newspaper quotes NYS
Department of Environmental
Conservation wildlife
pathologist as saying he
has received many dead bird
reports from NYC and
Buffalo; reports are being
investigated intensively.
Thursday,
8/19/99 Veterinary assistant from
Bronx Zoo phones NYS
Department of Environmental
Conservation requesting
laboratory results on zoo
samples; informed that NYS
Department of Environmental
Conservation wildlife
pathologist is finding
several causes but "no
common thread."
Flushing Hospital admits a
fourth elderly patient with
possible viral symptoms, who,
after a few days, develops
neurologic symptoms.
Flushing Hospital's chief of
Friday, infectious diseases recognizes
8/20/99 that in the past 1 to 2 weeks,
an unusually large number of
spinal fluid samples have been
drawn to test for meningitis or
encephalitis (usually only two
or three per year). Patients'
advanced age and pattern of
muscle weakness also do not fit
disease profile commonly seen at
the hospital.
Chief of infectious disease at
Flushing Hospital phones
director of Bureau of
Communicable Disease, NYC
(Approx. date) NYS Department of Health. Requests
agricultural veterinarian assistance in identifying
informs state public health disease causing encephalitis in
veterinarian that dead elderly patients, discusses
birds are being reported in possible need to rule out
the state. They discuss botulism. Health bureau director
need for diagnostic does not think described
Monday, laboratory testing and symptoms fit botulism. She sends
8/23/99 agree samples should be an epidemiologist to Flushing
sent to the National Hospital to review patient
Veterinary Services records and advises the chief of
Laboratories in Ames, Iowa, infectious disease to send
operated by Animal and cerebrospinal fluid samples to
Plant Health Inspection the virology laboratory at NYS
Service (APHIS) of U.S. Department of Health.
Department of Agriculture
(USDA).
Flushing Hospital admits a fifth
patient with neurological and
possible viral symptoms.
Several birds in outdoor
Wednesday, cage at Bronx Zoo die;
8/25/99 necropsies performed in
Bronx Zoo pathology
laboratory.
Chief of infectious disease,
Flushing Hospital, again phones
director of NYC Department of
Health, Bureau of Communicable
Disease, discusses whether to
try botulism antitoxin because
patients are not responding to
any other treatments. Flushing
Hospital is having problems
preparing and sending samples to
NYS Department of Health;
specimens need to be sent on dry
ice, which hospital does not
have. Flushing Hospital
neurologist reports seeing
another similar case during a
visit to NYC
Hospital−Queens.
Friday, To address the Flushing
8/27/99 physicians' concerns about
botulism, the director of the
city bureau of communicable
disease contacts Centers for
Disease Control and Prevention
(CDC) Foodborne and Diarrheal
Disease Program in Atlanta
(oversees botulism
surveillance). CDC experts agree
that botulism is unlikely but
that Flushing patients are
unusual. Director of the city
Bureau of Communicable Disease
decides to visit Flushing
Hospital the next day to gather
more information.
Sixth patient, elderly, admitted
at Flushing Hospital with viral
and possible encephalitis
symptoms.
Director and epidemiologist from
Bureau of Communicable Disease,
NYC Department of Health, visit
Saturday, Flushing Hospital to review
8/28/99 patients and patient records;
they learn another patient with
neurologic symptoms has just
been admitted.
Epidemiologists from NYC
Department of Health continue
interviewing patients and
families. They call hospitals in
Queens and nearby Brooklyn and
find three more suspected cases
of encephalitis, in addition to
five patients at Flushing
Hospital and NYC Hospital,
Queens.
Sunday,
8/29/99 Director of city Bureau of
Communicable Disease begins
contacting health officials
within CDC's Arboviral,
Enteroviral, and Viral Special
Pathogens Branches to request
assistance with investigating a
possible outbreak of unknown
infectious disease in NYC. Also
sends e-mail to NYS Department
of Health, Connecticut
Department of Health, and
departments of health in
surrounding counties.
Conference call between NYC
Department of Health, NYS
Department of Health, and
individuals in CDC's Division of
Vector-Borne Infectious
Diseases, Bioterrorism
Preparedness and Response
Project, and Division of Viral
and Rickettsial Disease.
Decision is made to send patient
specimens to NYS Department of
Wildlife pathologist at NYS Health for testing. State health
Department of Environmental department issues official
Conservation contacts chief invitation for CDC to assist
of virology laboratory for with outbreak investigation. CDC
NYS Department of Health, Epidemic Intelligence Service
requests testing of bird officer already assigned to New
samples. State laboratory York joins epidemiological
Monday, does not have reagents to investigation.
8/30/99 test for bird viruses.
(approx.) Laboratory chief suggests
sending to Cornell
University veterinary NYC Department of Health begins
laboratory, who refers the active surveillance for patients
wildlife pathologist to with encephalitis at hospitals
USDA/APHIS National throughout the NYC area.
Veterinary Services Broadcast fax also is sent to
Laboratories. alert NYC physicians about the
Queens disease cluster and to
ask that patients with similar
symptoms be reported
immediately.
One of the elderly patients with
serious neurologic symptoms dies
at Flushing Hospital; autopsy is
performed.
Another elderly patient dies at
Flushing Hospital of
encephalitis; autopsy is
performed. A seventh patient
(young adult) is admitted with
viral symptoms, rash, muscle
weakness.
(Approx. date) Human samples
from Flushing Hospital are
received by NYS Department of
Tuesday, Health virology laboratory by
8/31/99 way of NYC Department of Health.
CDC Epidemic Intelligence
Service officer from Atlanta
joins epidemiological
investigation in NYC. Evidence
from the environmental field
investigation suggests
mosquito-borne disease as
possible cause after numerous
mosquito-breeding sites and
mosquito larvae are found in
patients' backyards and
neighborhood.
State health department
laboratory reports positive test
results for flavivirus, further
evidence of mosquito-borne
disease agent.
Head of pathology, Bronx NYS Department of Health ships
Zoo, phones wildlife blood and spinal fluid samples
pathologist at NYS from patients at Flushing
Department of Environmental Hospital to CDC Division of
Vector-Borne Infectious
Wednesday, Conservation, who says he Diseases, and informs CDC
9/1/99 has examined about 400 dead laboratory by e-mail of negative
birds in August and is
sending samples to the results for St. Louis
laboratory at USGS National encephalitis by polymerase chain
Wildlife Health Center in reaction (PCR, or molecular
Wisconsin. biological) testing on the
previous day.
CDC Infectious Disease Pathology
Activity laboratory (Atlanta)
receives human brain tissue
sample from autopsy of a
Flushing patient.
State health department
laboratory reports to NYC health
department that it has a strong
reaction for St. Louis
encephalitis in human specimens,
using serological tests known to
cross-react with similar
viruses. NYC has never before
had a documented, locally
acquired human case of St. Louis
encephalitis.
NYC Department of Health has
received reports of 30 to 40
suspected human cases in
response to its health alerts
NYS Department of and contacting infectious
Environmental Conservation disease and neurology
wildlife pathologist departments in local hospitals.
contacts the USGS National
Wildlife Health Center
laboratory in Wisconsin to
Thursday, request help in testing CDC Division of Vector-Borne
9/2/99 bird samples. Instructed to Infectious Diseases receives
wait until Tuesday, 9/7, to samples of Flushing Hospital
avoid having samples in patients from NYS Department of
transit over the long Health.
holiday weekend.
Director of NYC Office of
Emergency Management receives a
call in late afternoon from head
of NYC Department of Health,
requesting assistance with
cleanup of suspected
mosquito-breeding site in Queens
area and preparation for rapid
implementation of mosquito
control if CDC confirms
mosquito-borne disease outbreak.
Flushing Hospital admits eighth
patient with possible viral
symptoms, muscle weakness, rash.
CDC Division of Vector-Borne
Infectious Diseases announces it
has positive results for St.
Louis encephalitis in human
samples by enzyme-linked
immunoabsorbent assay testing
(ELISA, a rapid test for virus
antibodies), and it has ruled
out several other viruses.
NYC publishes news releases
reporting that CDC has announced
an outbreak of St. Louis
encephalitis in New York City.
CDC Division of Vector-Borne
Infectious Diseases sends a
third Epidemic Intelligence
Service officer to NYC to
assist.
City Office of Emergency
Management and NYC health
department initiate mosquito
Friday, control activities and start a
9/3/99 public information hotline.
Health department disseminates
public information materials and
sends sanitarians to assist with
mosquito control and cleanup in
Queens area. Office of Emergency
Management provides interagency
coordination and arranges
emergency contracts for mosquito
control.
NYC Office of Emergency
Management and city health
department begin spraying for
mosquitoes in non-residential
areas.
Commissioner of NYC Office of
Emergency Management touches
base with Federal Bureau of
Investigation (FBI) about
outbreak of unusual infectious
disease in NYC so it can
possibly evaluate for criminal
(bioterrorist) involvement. City
health officials also in contact
with FBI.
Epidemiologist at NYC health
department finds out about large
numbers of dead birds from calls
to public hotline and public
comments at a news conference,
considers possible connection
between bird deaths and human
outbreak of St. Louis
encephalitis. She informs
officials of the Office of
Emergency Management, NYS health
Over Labor Day weekend: department, and CDC.
Animal health officials
become aware of human
outbreak of St. Louis
encephalitis through news Director of NYS arthropod-borne
releases, begin considering disease program joins outbreak
the possibility that team in NYC.
outbreak of unknown
infectious disease in birds
might be linked.
Saturday, At a mobile command unit, a
9/4/99 member of the public brings in a
dead bird. Director of NYS
Connecticut Agricultural arthropod-borne disease program
Experiment Station advises sending the bird to the
continues to trap wildlife pathologist at NYS
mosquitoes and responds to Department of Environmental
announcement of St. Louis Conservation.
encephalitis in NYC by
moving mosquito traps to
areas near the NYC outbreak
area. Researchers at CDC Infectious
Disease Pathology Activity
laboratory in Atlanta examine
human specimens from NYC,
observe evidence of viral
encephalitis, obtain positive
results for flavivirus in human
brain sample by
immunohistochemical testing
(testing for chemical evidence
of infection and immune system
response).
(Labor Day weekend) Response to
large outbreak of Escherichia
coli O157:H7 at Washington
County fair places large demand
on NYS Department of Health
resources.
Sunday,
9/5/99 City health department begins
daily alerts to area health
officials.
ProMED electronic mailing list
posts announcement of outbreak
of St. Louis encephalitis in
NYC.
NYC Office of Emergency
Management and health department
do aerial survey, identifying
Monday, Over Labor Day weekend, stagnant water in swimming pools
9/6/99 several more birds die at as possible mosquito-breeding
Bronx Zoo.
sites. They begin door-to-door
and call-in response to get
pools drained.
Wildlife pathologist at NYS
Department of Environmental
Conservation sends bird
samples to USGS National
Wildlife Health Center
laboratory. In cover letter
requesting bird testing, he
indicates NYC is
experiencing the highly
unusual event of a human
outbreak of St. Louis
encephalitis. City and state departments of
health, NYC Office of Emergency
Management, and CDC continue
outbreak response, including
telephone surveillance of
Tuesday, (Approx. date) NYS public hospitals for meningitis and
9/7/99 health veterinarian e-mails encephalitis cases, weekly fax
colleagues in other areas
where St. Louis alerts to New York City medical
encephalitis has occurred community, daily public
to see if bird die-offs communication and response
have been involved. All activities, and mosquito
responses indicate bird control.
die-offs have not been
involved. NYS public health
veterinarian reviews
information on Rocio virus,
known to cause bird
die-offs along with human
encephalitis outbreak in
South America, but it does
not seem a likely cause of
the New York outbreak.
Wildlife pathologist at NYS
Department of Environmental
Conservation sends bird
samples to USDA/APHIS
National Veterinary
Services Laboratories.
Indicates there is an
outbreak of St. Louis
encephalitis in humans in Entomologist from CDC Division
the same area where crows of Vector-Borne Infectious
are dying. Diseases arrives in NYC. Begins
mosquito collection in Queens
area to study extent of
outbreak.
Bronx Zoo head pathologist
receives and examines Health officials confirm first
slides from zoo birds that positive human case in Brooklyn
died in late August, (outside of Queens area). Based
compares to samples from on this case and increasing
birds that died over the reports of suspected cases
holiday weekend, finds they throughout the city, the city
Wednesday, have similar lesions health department and Office of
9/8/99 indicating possible Emergency Management begin
encephalitis. citywide mosquito control.
The National Wildlife Laboratory at CDC Division of
Health Center laboratory in Vector-Borne Infectious Diseases
Wisconsin receives birds begins testing serum samples
from NYS Department of from New York patients using
Environmental Conservation. virus-specific neutralization
assays (tests used to detect
parts of a specific virus) for
St. Louis encephalitis.
ProMED posts news that
Connecticut Agricultural
Experiment Station is
testing mosquitoes trapped
near NYC area for both St.
Louis encephalitis and
eastern equine
encephalitis, and it will
be 5 or 6 days before test
results are available.
Wildlife pathologist at NYS
Department of Environmental
Conservation sends more
crow samples to USGS
National Wildlife Health
Center laboratory in
Wisconsin, indicates he has
observed "gliosis" in brain
tissue (evidence of
degenerative lesion,
possible encephalitis).
USDA National Veterinary
Services Laboratories in
Iowa receives samples sent
on 9/8/99 by NYS Department
of Environmental
Conservation.
Bronx Zoo head pathologist
starts doing necropsies on
all birds that have died,
preserving samples. She
calls CDC in Atlanta;
referred to CDC Division of
Vector-Borne Infectious
Diseases in Fort Collins,
Colo.
Bronx Zoo head pathologist
phones chief of the
epidemiology and ecology
section at Division of
Vector-Borne Infectious
Diseases, who says the
division's laboratory is
not the appropriate one to
test exotic bird specimens.
Suggests specimens be sent
to USDA/APHIS National
Veterinary Services
Laboratories for testing.
They also discuss possible
human exposure at the Bronx
Zoo (needle-stick injury of
veterinary assistant). Third patient dies from viral
Thursday, Bronx Zoo head pathologist encephalitis.
9/9/99 makes a second phone call
to Division of Vector-Borne
Infectious Diseases, speaks
to the secretary and
requests forms for
submitting samples.
Secretary sends e-mail to
chief of epidemiology and
ecology section and to
section medical officer
regarding contact from the
Bronx Zoo and asking
whether approval is given
for sending samples.
Medical officer forwards
the e-mail to vertebrate
ecologist, who responds he
is willing to look at the
bird samples.
Bronx Zoo head pathologist
prepares and ships bird
tissue samples to National
Veterinary Services
Laboratories; in a cover
letter, she indicates
possible connection with
St. Louis encephalitis
outbreak in humans and her
concern about needle-stick
injuries among laboratory
workers. She also sends a
serum specimen from a Bronx
Zoo employee who suffered a
needle-stick injury and a
plasma specimen from a
flamingo to CDC Division of
Vector-Borne Infectious
Diseases.
Meeting held at Bronx Zoo,
update on bird deaths and
possible diseases. Zoo
officials decide to get an
outside consultant to help
with mosquito control.
Medical officer, CDC
Division of Vector-Borne
Infectious Diseases,
responds to vertebrate
ecologist by e-mail that he
talked to the head
pathologist at Bronx Zoo
this morning, learned that
the chief of epidemiology
and ecology section had
already told her that the
Division of Vector-Borne Assistant to NYC health
Infectious Diseases was not department epidemiologists sends
the right place to send an e-mail to the team of
bird specimens. The medical epidemiologists investigating
officer advised the the outbreak. E-mail indicates
vertebrate ecologist to receiving a call from the head
talk with the section chief veterinarian at the Bronx Zoo
before proceeding further. saying that many birds are dying
and they have not been able to
determine the cause. NYC health
department also has been
National Veterinary contacted by Bayside Historical
Services Laboratories in Society in Queens about dead
Iowa receives Guanay birds. Assistant suggests
cormorant, bald eagle, passing the information on to
flamingo, and tragopan the CDC Epidemic Intelligence
(pheasant) samples from Service veterinarian, who should
Bronx Zoo. let the CDC vertebrate ecologist
Friday, know when he arrives, because he
9/10/99 "may want to contact the zoo for
samples and perform a battery of
Head pathologist at Bronx tests for alphaviruses, and
Zoo is still concerned perhaps even St. Louis
about human safety in the encephalitis, on these birds."
laboratory while performing
bird necropsies. Contacts
the NYS agricultural
veterinarian to get NYC Department of Health
permission to send samples epidemiologists ask CDC
to National Veterinary vertebrate ecologist if bird
Services Laboratories. deaths and human disease could
Calls Cornell veterinary be related. He responds that
college; they suggest bird die-offs can be caused by
National Veterinary many things and the two
Services Laboratories. outbreaks probably are
Calls head veterinary coincidental.
medical officer, National
Veterinary Services
Laboratories, asks if he
would look at samples sent
directly from the Bronx
Zoo. Head veterinary
medical officer says he has
ruled out Newcastle disease
in samples already received
through NYS Department of
Environmental Conservation;
preparing to test for avian
influenza.
Head veterinary medical
officer for National
Veterinary Services Vertebrate ecologist from CDC
Laboratories phones Bronx Division of Vector-Borne
Saturday, Zoo head pathologist. Infectious Diseases arrives in
9/11/99 Results of serology testing NYC to conduct the bird
are negative for eastern, serosurvey (taking and testing
western, and Venezuelan samples of blood from live
equine encephalitis. Now birds).
waiting for virus
isolation.
NYC Department of Health e-mails
message about Bronx Zoo's
request to look at bird die-offs
to CDC vertebrate ecologist. He
responds that he hopes to meet
with head veterinarian of the
Bronx Zoo the next day.
Sunday,
9/12/99
(Approx. date) In the past 1 to
2 weeks, NYS Department of
Health's virology laboratory has
conducted numerous tests for St.
Louis encephalitis using PCR,
all with negative results.
CDC vertebrate ecologist visits
head veterinarian, Bronx Zoo,
and asks to gather blood samples
from live birds in the zoo.
Bronx Zoo head veterinarian
refuses because birds have been
dying in the zoo and they do not
want to expose them to
additional stress or infection.
Asks if the CDC vertebrate
ecologist would like to test
samples from dead birds and he
Connecticut Agricultural responds that he is unable to
Experiment Station obtains because he is currently doing
Monday, an encephalitic dead crow live-bird testing in
9/13/99 from Westport area (near investigating the human
NYC outbreak area), will outbreak.
attempt to isolate virus
from its brain tissue.
In Albany, NYS Department of
Health and CDC are hosting a
meeting of a work group on
encephalitis cases of unknown
etiology, associated with CDC's
unexplained deaths project.
Includes researchers from CDC
Atlanta, NYS health department,
and academic researchers,
including one from University of
California at Irvine.
National Veterinary
Services Laboratories
isolates a virus from bird
samples from Bronx Zoo and
NYS Department of
Environmental Conservation
and begins attempting to
identify it.
Bronx Zoo head pathologist
attempts to phone CDC
Division of Vector-Borne
Infectious Diseases to ask
about results on specimens NYS Department of Health/CDC
she has sent directly to conference continues on
Tuesday, them. encephalitis cases of unknown
9/14/99 etiology.
(Approx. date) National
Wildlife Health Center
laboratory in Wisconsin
isolates virus from bird
samples, obtains negative
results in testing for St.
Louis encephalitis and
eastern equine encephalitis
using reagents they have on
hand. National Wildlife
Health Center virologists
discuss the possibility of
a new strain of St. Louis
encephalitis or an exotic
disease.
National Veterinary
Services Laboratories
observes, by electron
microscopy, a
"flavi/toga-like virus, 40
nanometers in diameter." NYS Department of Health's E.
Serum-based tests indicated coli outbreak response is
negative results for gearing down.
eastern, western, or
Venezuelan equine
encephalitis viruses, or
St. Louis encephalitis Participants in the conference
virus. Researchers consider on encephalitis cases (including
possibility of a new strain officials from CDC Atlanta) hear
or virus. that USDA National Veterinary
Services Laboratories isolated a
virus it is unable to identify,
from dead birds from New York.
National Veterinary Conference participants suggest
Wednesday, Services Laboratories sending human tissue samples to
9/15/99 informs head pathologist at the University of California
Bronx Zoo about latest test researcher's laboratory so he
results. Bronx Zoo head can attempt to identify virus
pathologist sends paired with rapid PCR testing methods.
plasma samples (well and State health officials decide to
sick) from birds to do so both to test the
National Veterinary California researcher's testing
Services Laboratories. methods and also because,
although CDC is reporting
positive serologies on human
samples, the NYS Department of
(Approx. date) Director of Health has failed to obtain
National Wildlife Health positive results for St. Louis
Center talks with CDC encephalitis by PCR testing
Division of Vector-Borne after many attempts.
Infectious Diseases, branch
chief of arbovirus
diseases. They discuss what
virus could be killing
birds in New York.
CDC Division of
Vector-Borne Infectious
Diseases medical officer
calls back Bronx Zoo head
pathologist, suggests
discontinuing bird
necropsies until human
safety factors are
determined. Suggests
sending existing samples to
NYS Department of Health's
laboratory for faster
testing than Division of
Vector-Borne Infectious
Diseases would do at this
time on animal samples.
USDA National Veterinary Staff of virology laboratory,
Services Laboratories NYS Department of Health, sends
Thursday, contacts the CDC liaison human brain tissue samples from
9/16/99 officer at Veterinary several patients to researcher
Services at USDA/APHIS at University of California at
because of unusual Irvine.
properties of the virus it
has isolated and its lack
of reagents to identify
whether the virus could be
a human pathogen. Liaison
officer contacts CDC. CDC
contacts head veterinary
medical officer at National
Veterinary Services
Laboratories and asks for
virus isolate to be sent to
the Division of
Vector-Borne Infectious
Diseases in Fort Collins.
CDC recommends waiting
until Monday, 9/20/99, to
ship the isolate to avoid
having it in transit over
the weekend.
Bronx Zoo head pathologist
phones NYS Department of
Environmental Conservation
wildlife pathologist, who
reports having sent bird
samples to USGS National
Wildlife Health Center
laboratory.
Bronx Zoo head pathologist University of California
leaves message for and researcher receives brain
receives message from samples sent the previous day by
acting section chief of NYS Department of Health. He
Diagnostic and Reference, contacts officials at CDC's
CDC Division of Division of Viral and
Vector-Borne Infectious Rickettsial Disease in Atlanta,
Diseases. He expects Bronx informs them he has been invited
Zoo samples from National by NYS health department to
Veterinary Services assist in testing human samples.
Laboratories to arrive on He obtains information from
Friday, 9/21/99. chief of the CDC Infectious
9/17/99 Disease Pathology Activity
laboratory about his previous
findings from
Bronx Zoo head pathologist immunohistochemical testing of
attempts to establish brain tissue from NY patient.
contact with the U.S. Army
Medical Research Institute
of Infectious Diseases.
At CDC Division of Vector-Borne
Infectious Diseases, results of
testing for St. Louis
Bronx Zoo head pathologist encephalitis in human serum
calls chief of the virology specimens are inconclusive.
laboratory for the NYS
Department of Health. The
laboratory chief requests
samples of virus isolates
from National Veterinary
Services Laboratories and
advises on use of
laboratory hoods for
increasing human safety in
the zoo pathology
laboratory.
CDC entomologist returns to CDC
Saturday, Division of Vector-Borne
9/18/99 Infectious Diseases from NYC,
begins assembling data from
mosquito survey.
Bronx Zoo head pathologist
contacts National
Veterinary Services
Laboratories, provides
address for the virology
laboratory at the NYS
Department of Health,
requests that virus isolate
samples of Bronx Zoo birds
be sent there.
University of California
Monday, researcher's laboratory purifies
9/20/99 RNA from human brain samples and
National Veterinary synthesizes reagents in
Services Laboratories ships preparation for PCR testing.
virus isolates to the
Division of Vector-Borne
Infectious Diseases. Virus
isolates shipped were made
from tissues of birds
originally submitted by NYS
Department of Environmental
Conservation and the Bronx
Zoo.
Date Phase 3: Convergence
Connecticut Agricultural Experiment Station
reports isolating virus from brain tissue of a
dead crow and from mosquitoes; they appear to be
the same virus. Possible implication: If the
virus is St. Louis encephalitis, it can kill and
is killing birds; human and bird outbreaks may be
related.
Chief of arbovirus diseases branch at CDC
Division of Vector-Borne Infectious Diseases
contacts Connecticut Agricultural Experiment
Station, determines testing protocols were not
specific for St. Louis encephalitis. CDC requests
that Connecticut Agricultural Experiment Station
send virus isolates to the laboratory at CDC
Division of Vector-Borne Infectious Diseases for
confirmation.
Tuesday, 9/21/99 Vertebrate ecologist, CDC Division of
Vector-Borne Infectious Diseases, returns to Fort
Collins laboratory from NYC.
CDC Division of Vector-Borne Infectious Diseases
receives virus isolates from head veterinary
medical officer at National Veterinary Services
Laboratories and begins testing for several
related viruses.
Veterinary pathologists at U.S. Army Medical
Research Institute of Infectious Diseases respond
to contact from the head pathologist at the Bronx
Zoo, agree to test bird samples.
University of California researcher initiates
genomic sequence studies on human brain samples.
Director of Bureau of Communicable Disease, NYC
Department of Health, hears for the first time
that the wildlife pathologist at NYS Department
of Environmental Conservation had been finding
encephalitis in dead birds. Calls CDC. The city
health department begins helping to collect dead
birds. NYS public health veterinarian establishes
surveillance system and database for ill and dead
birds.
Vertebrate ecologist at CDC Division of
Vector-Borne Infectious Diseases begins testing
samples obtained through bird serosurvey, hears
about news from Connecticut Agricultural
Experiment Station, sets up tests for other
flaviviruses besides St. Louis encephalitis.
CDC Division of Vector-Borne Infectious Diseases
obtains positive test result for flavivirus in
bird specimens from National Veterinary Services
Laboratories.
Wednesday, 9/22/99
Bronx Zoo head pathologist phones U.S. Army
Medical Research Institute of Infectious
Diseases, learns that it has negative test
results on Bronx Zoo bird samples for eastern,
western, and Venezuelan equine encephalitis.
Bronx Zoo head pathologist ships more samples to
U.S. Army Medical Research Institute of
Infectious Diseases. Bronx Zoo head pathologist
talks with director of virology laboratory at NYS
Department of Health, learns Connecticut
Agricultural Experiment Station laboratory has
isolated virus in both birds and mosquitoes.
Bronx Zoo head pathologist contacts CDC Division
of Vector-Borne Infectious Diseases, informs them
of results from U.S. Army Medical Research
Institute of Infectious Diseases.
Late evening: Using PCR technique, University of
California researcher finds genetic patterns of a
flavivirus in brain samples of three New York
patients.
University of California researcher phones
virologist at NYS Department of Health
laboratory, reports he has found genetic evidence
of flavivirus in brain samples of three human
patients. Begins comparing flavivirus genomes
from two patients to genome patterns available in
GenBank (a national database of genetic
information on disease agents).
CDC Division of Vector-Borne Diseases again
contacts Connecticut Agricultural Experiment
Station. The Station is shipping virus isolates.
CDC Division of Vector-Borne Infectious Diseases
completes retesting of four human specimens
previously tested for St. Louis encephalitis. Now
testing for St. Louis encephalitis, West Nile,
Japanese encephalitis, Powassan, dengue, and
yellow fever viruses to rule out possibility of
infection by a closely related virus. Retesting
produces high reactivity with West Nile virus.
Retesting commences on 24 more specimens. Strong
reaction for West Nile virus in human body fluid
samples using enzyme-linked immunoabsorbent assay
(ELISA). Informs CDC Atlanta.
CDC laboratory designs PCR test for West Nile
Thursday, 9/23/99 virus and identifies "West Nile-like" virus in
birds from virus isolates from USDA/APHIS
National Veterinary Services Laboratories.
Bronx Zoo head pathologist hears from veterinary
pathologists at U.S. Army Medical Research
Institute of Infectious Diseases that they have
preliminary identification of St. Louis
encephalitis or a related virus; requesting
normal control samples for flamingo and tragopan.
Bronx Zoo head pathologist phones head veterinary
medical officer at National Veterinary Services
Laboratories, asks why virus isolate samples were
not sent to the NYS Department of Health
laboratory as requested. National Veterinary
Services Laboratories will ship isolates to NYS
Department of Health on September 27 because of
the need to send samples with adequate virus
titer and to avoid shipping over the weekend.
Mid-afternoon: Teleconference between Bronx Zoo
head pathologist and Division of Vector-Borne
Infectious Diseases, who report they have tested
isolates from National Veterinary Services
Laboratories and have obtained positive results
for flavivirus. Bronx Zoo head pathologist sends
more samples to Division of Vector-Borne
Infectious Diseases.
NYS Department of Health gets phone and fax
messages from University of California
researcher. From samples from NYS Department of
Health, he has determined virus is not St. Louis
encephalitis but appears most closely related to
Kunjin virus and West Nile virus. Researcher also
informs others at University of California at
Irvine.
Director of virology laboratory at NYS Department
of Health calls chief of arbovirus diseases
branch, CDC Division of Vector-Borne Infectious
Diseases; informs him of the University of
California researcher's results. State laboratory
officials inform NYS Health Commissioner.
Division of Vector-Borne Infectious Diseases
completes retesting of 24 human specimens,
results show high reactivity with West Nile
virus. Amplifies ribonucleic acid of virus from
human brain tissue for PCR testing.
Friday, 9/24/99 Conference call including officials from CDC
Division of Vector-Borne Infectious Diseases, CDC
Atlanta, NYS Department of Health, NYC Department
of Health, Connecticut Department of Health, and
Connecticut Agricultural Experiment Station, and
Bronx Zoo head pathologist. CDC announces West
Nile virus in birds, does not want to announce
publicly that West Nile virus has been found in
humans until genome sequencing is completed and
diagnosis is confirmed, expected early the
following week. CDC publishes news release on
West Nile virus found in birds.
Head veterinary medical officer at National
Veterinary Services Laboratories contacts
headquarters for Veterinary Services at USDA
Animal and Plant Health Inspection Service and
also the office of the veterinarian-in-charge for
the New York area; informs them of CDC's finding
of West Nile-like virus in birds.
Friday evening: University of California
researcher informs deputy director of Division of
Viral and Rickettsial Diseases, CDC Atlanta, of
finding virus related to Kunjin virus or West
Nile virus in humans by genomic sequencing.
Partial genome sequencing of human specimens at
CDC Division of Vector-Borne Infectious Diseases
indicates probable final diagnosis of West Nile
virus in humans. Continuing analysis of samples
from the bird serosurvey produces evidence of
West Nile virus-neutralizing antibodies in
healthy birds. West Nile virus confirmed in
specimens obtained from the Connecticut
Agricultural Experiment Station.
CDC Division of Vector-Borne Infectious Diseases
contacts researcher at University of California
at Irvine. They compare their findings and
discuss plans for public announcements and
publications.
Saturday, 9/25/99
Connecticut Agricultural Experiment Station
obtains a live Cooper's hawk with neurologic
symptoms; bird dies the next day and is tested
for viral identification.
News media breaks story, West Nile virus in birds
and West Nile virus or Kunjin virus in people,
explains CDC at first misidentified the virus as
St. Louis encephalitis.
ProMED reports a 75-year-old resident of Toronto,
Canada, has St. Louis encephalitis after visiting
New York City.
CDC Division of Vector-Borne Infectious Diseases
expands dead bird surveillance, soliciting bird
Sunday, 9/26/99 samples in affected states and asking that
samples be submitted through state wildlife
pathologists.
Chief of epidemiology section, bacterial zoonoses
branch, at CDC Division of Vector-Borne
Infectious Diseases goes to NYC to help the NYC
health department conduct a human serosurvey
(collection of blood samples from random sample
of humans in the outbreak area).
Researcher at Pasteur Institute, Paris, posts an
offer on ProMED to assist scientists studying the
New York outbreak by providing West Nile virus
genome sequence patterns that have not yet been
published.
Researchers at CDC Division of Vector-Borne
Infectious Diseases talk to foreign researchers
to establish a collaboration.
Monday, 9/27/99
Evening: University of California researcher
responds on ProMED to offer of assistance from
researcher at Pasteur Institute; gives detailed
report on his work to date in identifying
"Kunjin/West Nile virus" in humans.
USDA Animal and Plant Health Inspection Service
is officially notified by CDC that "West
Nile-like virus," rather than St. Louis
encephalitis, is responsible for the human
encephalitis outbreak in New York.
CDC announces it has established that human
outbreak in New York is due to West Nile-like
virus. Involved agencies receive a large number
of news media contacts and requests for
information from the public.
Human serosurvey (collection of blood samples) in
NYC area begins, supported by six Epidemic
Intelligence Service (EIS) officers from CDC and
over 100 personnel from the NYC health
department.
(Approx. date) Preliminary results from bird
serosurvey indicate an infection rate greater
than 50 percent for birds in northeast Queens,
providing further evidence of where outbreak may
have originated.
Tuesday, 9/28/99
Daily conference calls are initiated among
agencies participating in the outbreak response.
USDA/APHIS veterinary services headquarters
notifies others in APHIS and the Secretary's
Advisory Committee on Foreign Animal and Poultry
Diseases about West Nile-like virus outbreak in
NY area.
(Approx. date) CDC and international scientists
find a link between the NYC strain of West Nile
virus and a recent strain from Israel.
Briefing of staff for New York and Connecticut
congressional representatives by CDC's acting
deputy director for science and public health.
Wednesday, 9/29/99
USDA Animal and Plant Health Inspection Service
(APHIS) coordinates with state officials and
cooperating federal agencies to address impact of
West Nile virus outbreak on agricultural
industry.
USDA receives reports of a horse on Long Island
possibly infected with West Nile virus.
Thursday, 9/30/99
Division of Vector-Borne Infectious Diseases
isolates virus from Culex mosquitoes collected in
Queens on September 12 and 13, identifies West
Nile virus.
USDA Animal and Plant Health Inspection Service
plans diagnostic testing, inoculation studies,
surveillance.
Friday, 10/1/99 Foreign animal disease diagnostician at USDA
Animal and Plant Health Inspection Service
investigates a suspicious horse death on eastern
Long Island and submits tissue samples to APHIS
National Veterinary Services Laboratories for
diagnosis.
Saturday, 10/2/99 CDC identifies West Nile virus in infected birds
submitted from New Jersey.
Sunday, 10/3/99 (Approx. date) Sixth human death from West Nile
virus (Nassau County resident).
National Veterinary Services Laboratories
receives samples from Long Island horse; begins
Tuesday, 10/5/99 virus isolation.
ProMED posting: Birds found positive for West
Nile virus in New Jersey.
(Approx. date) USGS National Wildlife Health
Center laboratory in Wisconsin sends virus
isolates from testing of birds begun in early to
mid-September to CDC Division of Vector-Borne
Infectious Diseases. CDC laboratory confirms West
Wednesday, 10/6/99 Nile virus in the samples.
The human serosurvey conducted by the NYC health
department and CDC is completed.
USDA Animal and Plant Health Inspection Service
Thursday, 10/7/99 distributes guidelines for investigating
suspected West Nile virus cases in livestock and
poultry.
Tissues, including brain tissue, from a second
Saturday, 10/9/99 horse from Long Island are received at National
Veterinary Services Laboratories, duplicates also
sent to CDC.
CDC and other federal agencies provide
information about West Nile virus outbreak in
relation to bioterrorism, in anticipation of a
story to be released the following day in The New
Yorker that indicates possible connection between
outbreak and bioterrorist activities by Iraq.
Sunday, 10/10/99 USDA Animal and Plant Health Inspection Service
sends early response team, including veterinary
pathologist, epidemiologist, and foreign animal
disease diagnostician, to investigate reports of
several horse deaths on Long Island. At the
request of NYS animal health officials, the APHIS
team works with state personnel, a local
veterinarian, and horse owners to conduct an
epidemiological investigation and examine
affected animals. Eight horse deaths and 18
affected animals are identified.
Article published in The New Yorker suggesting
Monday, 10/11/99 West Nile virus outbreak could have been
deliberately introduced by Iraq. More news media
and public response.
National Veterinary Services Laboratories
Tuesday, 10/12/99 isolates virus from horse samples from Long
Island, sends to CDC Division of Vector-Borne
Infectious Diseases for identification.
(Approx. date) USGS National Wildlife Health
Center laboratory receives reagents from CDC so
it can test for West Nile virus in wildlife.
Wednesday, 10/13/99
ProMED posting, University of California
researcher responds to requests for West Nile
virus primers and protocols for RT-PCR test,
publishes protocol on ProMED.
CDC examines isolates of West Nile virus from
horse samples sent by National Veterinary
Thursday, 10/14/99 Services Laboratories. Initially obtains negative
results by PCR testing but later confirms
National Veterinary Services Laboratories'
isolation of virus.
U.S. Army Medical Research Institute of
Friday, 10/15/99 Infectious Diseases agrees to provide laboratory
support for National Veterinary Services
Laboratories and animal health investigations.
National Veterinary Services Laboratories
completes PCR testing of virus isolated from two
Saturday, 10/16/99 Long Island horses, using genetic sequence
provided by CDC. Both horses test positive for
West Nile virus.
U.S. Army Medical Research Institute of
Infectious Diseases provides Vickers Unit
(portable biosafety level 3 laboratory),
Monday, 10/18/99 requested and paid for by USDA Animal and Plant
Health Inspection Service, to Bronx Zoo so it can
safely perform necropsies and prepare samples for
testing.
CDC Division of Vector-Borne Infectious Diseases
reports serologic evidence of West Nile virus in
horses.
Tuesday, 10/19/99
NYS agricultural commissioner issues a press
release reporting that horse deaths and illnesses
in Long Island area were likely due to West
Nile-like virus.
Memo from NYS agricultural veterinarian and NYS
public health veterinarian summarizing confirmed
cases of West Nile virus in horses, birds, and
humans (56 confirmed cases with seven deaths).
Wednesday, 10/20/99
USDA Animal and Plant Health Inspection Service
notifies agricultural commissioners and state
veterinarians along the East Coast that West Nile
virus has been found in horses on Long Island,
NY.
USDA Animal and Plant Health Inspection Service
notifies representatives of the horse industry
that West Nile virus has been found in Long
Island horses, provides informational materials.
Thursday, 10/21/99
Many postings on ProMED about whether
transcontinental airplanes are sprayed for
mosquitoes.
CDC Division of Vector-Borne Infectious Diseases
and co-authors submit article for publication in
Science, linking NYC virus strain to a strain of
West Nile virus from Israel. Later published in
12/17/99 issue, along with paper from Connecticut
Agricultural Experiment Station research group on
its isolation of West Nile virus in Cooper's hawk
Friday, 10/22/99 and other species.
ProMED posts update from CDC, West Nile virus has
been identified in a variety of birds, no human
cases were reported after 9/22/99. Posting
stating that China has placed an import ban on
U.S. horses.
(Approx. date) Researchers from USGS National
Wildlife Health Center obtain a blood sample from
Saturday, 10/23/99 a migrating bird in the Bronx. CDC later isolates
West Nile virus from this sample, providing
evidence that migratory birds might transport the
virus.
City department of health and Office of Emergency
Monday, 10/25/99 Management end the public hotline. Approximately
150,000 calls have been processed since it began
on 9/3/99.
The Division of Vector-Borne Infectious Diseases
reports that a dead crow infected with West Nile
Thursday, 10/28/99 virus has been collected from Baltimore, Md.
(submitted by the Maryland Department of Health
through the USGS National Wildlife Health
Center).
European Union notifies USDA Animal and Plant
Health Inspection Service of import restrictions
on horses from New York, New Jersey, and
Connecticut.
Friday, 10/29/99
USDA Animal and Plant Health Inspection Service
notified that Mexico will not accept live poultry
from areas affected by West Nile virus.
Workshop co-sponsored by Department of Health and
Monday, 11/8/99 − Human Services, CDC, and USDA held in Fort
Tuesday, 11/9/99 Collins, Colo. Participants include most agencies
and individuals involved in outbreak response.
Note: Events involving crossover between animal and health outbreaks before
convergence phase are represented in bold type.
Related Publications
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Lessons from the 1999 West Nile Encephalitis Outbreak. Atlanta, Ga.: Centers
for Disease Control and Prevention, July 2000.
-----. Epidemic/Epizootic West Nile Virus in the United States: Guidelines
for Surveillance, Prevention, and Control. Atlanta, Ga.: Centers for Disease
Control and Prevention, March 2000.
New York State Department of Health. New York State West Nile Virus Response
Plan. Albany, N.Y.: New York State Department of Health, May 2000.
Wildlife Conservation Society. Proceedings of the West Nile Virus Action
Workshop. New York, N.Y.: Wildlife Conservation Society, Jan. 19-21, 2000.
Anderson, J.F., T.G. Andreadis, C.R. Vossbrinck, and others. "Isolation of
West Nile Virus From Mosquitoes, Crows, and a Cooper's Hawk in Connecticut."
Science, Vol. 286, No. 5448 (Dec. 17, 1999), p. 2331.
Nolen, R.S. "Veterinarians Key to Discovering Outbreak of Exotic
Encephalitis." Journal of the American Veterinary Medical Association,
http://www.avma.org/onlnews/javma/nov99/s111599a.asp (cited Nov. 15, 1999).
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Manduca, P.P. Calle, B.L. Raphael, T.L Clippinger, T. Larsen, J. Smith, R.S.
Lanciotti, N.A. Panella, and T.S. McNamara. "Pathology of Fatal West Nile
Virus Infections in Native and Exotic Birds During the 1999 Outbreak in New
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Asnis, D., R. Conetta, A. Teixeira, and others. "The West Nile Virus
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Centers for Disease Control and Prevention. "Outbreak of West Nile-Like
Viral Encephalitis--New York, 1999." Morbidity and Mortality Weekly Report,
Vol. 48, No. 38 (Oct. 1, 1999), pp. 845-49.
-----. "Update: West Nile-like Viral Encephalitis--New York, 1999."
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890-92.
Cheng, G.S. "West Nile Virus: Physician Reports Will Be Crucial." Family
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of a Kunjin/West Nile-like Flavivirus in Brains of Patients With New York
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1261-62.
Enserink, M. "Groups Race to Sequence and Identify New York Virus." Science,
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-----. "New York's Lethal Virus Comes From Middle East, DNA Suggests."
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Lanciotti, R.S., J.T. Roehrig, V. Deubel, and others. "Origin of the West
Nile Virus Responsible for an Outbreak of Encephalitis in the Northeastern
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Shieh, W.J., J. Guarner, M. Layton, A. Fine, J. Miller, D. Nash, G.L.
Campbell, J.T. Roehrig, D. J. Gubler, and S.R. Zaki. "The Role of Pathology
in an Investigation of an Outbreak of West Nile Encephalitis in New York,
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Comments From the Centers for Disease Control and Prevention
Comments From the New York City Department of Health
(201082)
Table 1: Examples of Surveillance and Laboratory Workload
Experienced by Selected Involved Agencies During and
Since the West Nile Outbreak 13
Table 2: Detailed Chronology of Events in the West Nile Virus
Outbreak, 1999 40
Figure 1: Transmission of St. Louis and West Nile Viruses 6
Figure 2: Timeline of 1999 West Nile Virus Outbreak 9
Figure 3: Examples of Migratory Patterns of Three Bird Species Susceptible
to West Nile 16
1. Although the chance that terrorists may use biological materials may
increase over the next decade, conventional explosives and firearms continue
to be the weapons of choice for terrorists. Terrorists face considerable
obstacles in developing biological weapons. See Combating Terrorism: Need
for Comprehensive Threat and Risk Assessments of Chemical and Biological
Attacks (GAO/NSIAD-99-163, Sept. 1999) and Combating Terrorism: Observations
on the Threat of Chemical and Biological Terrorism (GAO/T-NSIAD-00-50, Oct.
20, 1999).
2. Emerging infectious diseases include those whose incidence in humans has
increased within the past two decades or threatens to increase in the near
future.
3. According to a New York City Department of Health official, these
patients were initially seen by different physicians, as commonly occurs in
any hospital, and it was not until a single infectious disease consultant
reviewed their cases that the opportunity to see these patients as part of a
cluster presented itself.
4. The City Department of Health conducts surveillance for pesticide-related
morbidity by monitoring calls to the Department's Poison Control Center.
5. Due to increased surveillance since the initial outbreak, a new species
of mosquito, Aedes japonicus, has been found to carry the virus.
6. Massachusetts, Rhode Island, Connecticut, New York State, New York City,
Pennsylvania, New Jersey, Delaware, Maryland, the District of Columbia,
Virginia, North Carolina, South Carolina, Georgia, Florida, Alabama,
Mississippi, Louisiana, and Texas.
7. Connecticut, Delaware, Maryland, Massachusetts, New York, New Jersey, and
Rhode Island.
8. Developed in partnership with National Atlas of the United States,
http://www.nationalatlas.gov.
9. Horses are thought to be terminal or "dead-end" hosts, in that they can
be infected with the virus, but the virus does not develop in their blood at
sufficient quantities to reinfect mosquitoes.
10. As of August 2000, no clinical signs of the virus had been reported in
poultry in the United States, according to USDA.
11. Officials indicated that most critical was the collaborative
relationship in place between the health department and the Office of
Emergency Management due to the bioterrorism planning efforts. This
collaboration helped facilitate the rapid mobilization of emergency control
measures, establishment of the public hotline, and rapid mobilization of
staff over the holiday weekend to assist in canvassing local neighborhoods
with educational materials.
12. Wun-Ju Shieh, Jeannette Guarner, Marci Layton, Annie Fine, James Miller,
Denis Nash, Grant L. Campbell, John T. Roehrig, Duane J. Gubler, and Sherif
R. Zaki, "The Role of Pathology in an Investigation of an Outbreak of West
Nile Encephalitis in New York, 1999," Emerging Infectious Diseases, Vol. 6,
No. 4 (May-June 2000).
13. Institute of Medicine, Public Health Systems and Emerging Infections:
Assessing the Capabilities of the Public and Private Sectors, Workshop
Summary (Washington D.C.: National Academy Press, November 2000), p. 5.
14. Institute of Medicine and National Research Council, Chemical and
Biological Terrorism: Research and Development to Improve Civilian Medical
Response (Washington D.C.: National Academy Press, 1999), p. 66.
15. Emerging Infectious Diseases: Consensus on Needed Laboratory Capacity
Could Strengthen Surveillance (GAO/HEHS-99-26, Feb. 1999), p. 2.
16. Public Health Systems and Emerging Infections, p. 4.
17. An involved official indicated that these problems were improved with
the implementation of a standard format and agenda for each call.
18. M. Enserink, "Origins of New, Booming Diseases,"
http://sciencenow.sciencemag.org/cgi/content/full/2000/717/1 (cited July 17,
2000).
19. Chemical and Biological Terrorism, p. 68.
20. Chemical and Biological Terrorism, p. 72.
21. Reagents are chemicals used in laboratory tests to indicate the presence
of a virus or other substance.
22. During the outbreak, one of the biggest concerns of the veterinary
pathologist at the Bronx Zoo was the safety of laboratory workers at the zoo
who were handling sick or dead birds. At one point before the virus was
identified, a veterinarian who was euthanizing a dying flamingo stuck
himself with a needle. Because the pathologist surmised that the animal and
human outbreaks were related, this event heightened her concerns about
identifying the virus.
23. Specifically, according to information provided by a Wildlife Health
Sciences, Wildlife Conservation Society researcher, a serologic survey of
the Wildlife Conservation Society/Bronx Zoo collection was performed to
confirm infection of clinical cases, assess the extent of West Nile
exposure, and investigate when the virus was introduced to the collection.
24. According to CDC, West Nile virus was not included in the original
battery of antigens in the tests performed at this point because there are
30 possible antigens to include and West Nile had never before been seen in
the Western Hemisphere. Other experts indicated that this was a reasonable
conclusion at the time.
25. Chemical and Biological Terrorism, p. 73.
26. Biosafety Level-3 pathogens are considered serious or lethal with the
potential for aerosol transmission. Biosafety Level-4 pathogens are
dangerous, exotic agents posing high risk of life-threatening disease that
also are transmitted through the air and with an unknown risk of
transmission; Biosafety Level-4 pathogens have no vaccines or drugs
available for treatment. Officials told us that three federal laboratories
have Biosafety Level-4 capacity and that an inventory of Biosafety Level-3
laboratories is currently under way.
27. Critical biologic agents are those considered by CDC to be of potential
concern for bioterrorism and which must be registered with CDC when acquired
or transported. CDC has classified laboratories based on their biosafety and
containment capacities and other factors, level A, for example, representing
those with low-level biosafety facilities and level D representing those
with the highest-level containment and expertise in the diagnosis of rare
and dangerous biological agents. CDC reported that in fiscal year 1999, 19
of 43 funded states or localities self-reported a level C laboratory
capability for at least four of the critical biologic agents. According to
CDC, level C capability requires a Biosafety Level-3 facility.
28. Specifically, this official indicated that there are 9 Biosafety Level-3
veterinary laboratories that can study Biosafety Level-3 pathogen-infected
animals, and fewer than 10 additional veterinary laboratories that have
Biosafety Level-3 facilities for doing diagnostics or other nonanimal work.
29. Officials told us that since the West Nile outbreak last fall, funding
for these efforts in the state has increased.
30. E. coli are normal bacterial inhabitants of the intestines of most
animals, including humans, where they suppress the growth of harmful
bacteria and synthesize vitamins. However, a minority of strains cause
illness in humans. E. coli O157:H7, first identified as a human pathogen in
1982, is a strain that causes severe abdominal cramping and diarrhea that
can become heavily bloody. Although people usually get well without
treatment, the illness can be fatal.
31. CDC's Division of Vector-Borne Infectious Diseases, Arbovirus Disease
Branch, functions as a World Health Organization Collaborating Center for
Reference and Research on Arboviruses.
32. CDC officials from Atlanta were also involved in the discussion
regarding involving the researcher. Because tests can take a considerable
amount of time, a key state official involved in the decision indicated that
test results were not expected for weeks or months. Consequently, officials
did not inform the Fort Collins laboratory scientists that samples had been
given to the California laboratory.
33. The laboratory response network, which would link clinical laboratories
to public health agencies, is discussed in a report containing
recommendations of a CDC workgroup. See Centers for Disease Control and
Prevention, "Biological and Chemical Terrorism: Strategic Plan for
Preparedness and Response: Recommendations of the CDC Strategic Planning
Workgroup," Morbidity and Mortality Weekly, Vol. 49, No. RR-4 (April 21,
2000).
34. The workshop also concluded that specialized laboratory techniques in
modern biology and the skilled personnel needed to perform those tests are
usually too costly for most laboratories but could be obtained through the
use of a regional system and private-public partnership. See Public Health
Systems and Emerging Infections, p. 21.
35. The plan similarly addresses goals and strategies related to other
lessons learned discussed in this report, including improving disease
surveillance and outbreak response; applied research to develop diagnostic
tests, drugs, vaccines, and surveillance tools; public health infrastructure
and training; and disease prevention and control. See Centers for Disease
Control and Prevention, Preventing Emerging Infectious Diseases: A Strategy
for the 21st Century (Atlanta, Ga.: U.S. Department of Health and Human
Services, 1998).
36. The New Yorker (Oct. 18 and 25, 1999), pp. 90-107.
37. The cult's intent was to incapacitate people so they would be unable to
vote in a local election. Because the crime was politically motivated, the
Federal Bureau of Investigation subsequently considered the incident to be
an act of terrorism. Two former members pleaded guilty to tampering with
consumer products under the Federal Anti-Tampering Act of 1983. They were
each sentenced to 4-1/2 years in prison. See Food Safety: Agencies Should
Further Test Plans for Responding to Deliberate Contamination
(GAO/RCED-00-3, Oct. 1999), pp. 3-4.
38. In part, this project was initiated when researchers realized that what
were thought to be new diseases or pathogens had actually been causing
illness and deaths in past years. For example, after the serious outbreak of
Legionnaire's disease in 1976 in Philadelphia, in which 221 people fell ill
and 34 died, investigations identified cases in 1947 and an outbreak in 1957
that were previously unrecognized. Starting in 1995, under this project,
surveillance for unexplained deaths and critical illnesses occurred first in
four, and now in six states. This surveillance is considered to serve as an
early warning system for dangerous microbes as well as a focal point for
research on new tests.
39. This point was emphasized in the report of the CDC Strategic Planning
Workgroup. The report states that the epidemiologic skills, surveillance
methods, diagnostic techniques, and physical resources required to detect
and investigate unusual or unknown diseases are similar to those needed to
identify and respond to an attack with a biological agent. See Centers for
Disease Control and Prevention, "Biological and Chemical Terrorism," p. 4.
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