 |
|
West Nile Virus
Table of Contents
General Information
What Is It?
West Nile virus (WNV) has emerged in recent
years in temperate regions of Europe,
Africa,
Israel,
and North America, presenting a threat to public
health, equine health, and since 1999, the health of bird populations.
The most serious manifestation of infection is fatal encephalitis
(inflammation of the brain) in humans and horses, as well as mortality
in certain domestic and wild birds.
Prior to August 1999, WNV had never been reported in the
Western Hemisphere. In 1999, 62 cases of severe
disease, including seven deaths, occurred in the
New York City area. In 2000,
21 human cases occurred in the New York
City area, northern New
Jersey, and southwest
Connecticut. In 2003, most
states in the
U.S. had
recovered WNV in humans, horses, and birds.
What Are the Symptoms of
WNV?
Most infections are mild, and symptoms include fever, headache, and
body aches, often with skin rash and swollen lymph nodes. Following
transmission by an infected mosquito, WNV multiplies in the
person’s blood system and crosses the blood-brain barrier to reach
the brain. The virus interferes with normal central nervous system
functioning and causes inflammation of brain tissue. More severe
infection may be marked by headache, high fever, neck stiffness, stupor,
disorientation, coma, tremors, convulsions, muscle weakness, paralysis,
and rarely, death.
How Does
West NileVirus Spread?
People get WNV from the bite of a mosquito that is infected with WNV.
Mosquitoes become infected when they feed on infected birds, which may
circulate the virus in their blood for a few days. After an incubation
period of 10 days to 2 weeks, infected mosquitoes can transmit WNV virus
to humans and animals while biting to take blood.
How Is WNV Infection
Treated?
There is no specific treatment for WNV. In more severe cases,
intensive supportive therapy is indicated, i.e., hospitalization,
intravenous (IV) fluids, airway management, respiratory support
(ventilator) if needed, prevention of secondary infections (pneumonia,
urinary tract, etc.), and good nursing care. Currently there is no
vaccine for WNV.
What Should I
Do if I Think I Have WNV?
Milder WNV illness improves on its own, and people do not necessarily
need to seek medical attention for this infection though they may choose
to do so. If you develop symptoms of severe WNV illness, such as
unusually severe headaches or confusion, seek medical attention
immediately. Severe WNV illness usually requires hospitalization.
Pregnant women and nursing mothers are encouraged to talk to their
doctor if they develop symptoms that could be WNV.
What Is the
Risk of Getting Sick from WNV?
-
People over 50 at higher risk to get sick. People over the
age of 50 are more likely to develop serious symptoms of WNV if they do
get sick and should take special care to avoid mosquito bites.
-
Being outside means you're at risk. The more time you're
outdoors, the more time you could be bitten by an infected mosquito. Pay
attention to avoiding mosquito bites if you spend a lot of time outside,
either working or playing.
-
Risk through medical procedures is very low. All donated
blood is checked for WNV before being used. The risk of getting WNV
through blood transfusions and organ transplants is very small, and
should not prevent people who need surgery from having it. If you have
concerns, talk to your doctor.
-
Pregnancy and nursing do not increase risk of becoming
infected withWNV. The risk thatWNV
may present to a fetus or an infant infected through breastmilk is still
being evaluated. Talk with your care provider is you have
concerns.
What Can I Do to
Prevent WNV?
The easiest and best way to avoid WNV is to prevent mosquito bites.
-
When you are outdoors, use insect repellents containing DEET (N,
N-diethyl-meta-toluamide). Follow the directions on the package.
-
Many mosquitoes are most active at dusk and dawn. Be sure to use
insect repellent and wear long sleeves and pants at these times or
consider staying indoors during these hours. Light-colored clothing can
help you see mosquitoes that land on you.
-
Make sure you have good screens on your windows and doors to keep
mosquitoes out.
-
Get rid of mosquito breeding sites by emptying standing water from
flower pots, buckets and barrels. Change the water in pet dishes and
replace the water in bird baths weekly. Drill holes in tire swings so
water drains out. Keep children's wading pools empty and on their sides
when they aren't being used.
An educational pamphlet on the
West Nile Virus, along with other
educational pamphlets, is available for free download here.
Visit the CDC Website to learn how to
“Fight the
Bite”and Protect Yourself
Against West
Nile Virus.
Additional Resources
CLINICIAN/CONSUMER
EID Cover Journal (Vol 7 No 4
)
Neither signed nor dated, The Mosquito Net was
retained by Sargent until the end of his life and has long been ranked
among his best "private" works-small paintings done for his own
delectation rather than for a patron. The woman who posed for the
painting was Marion Alice (Polly) Barnard, whose father,
Frederick, was a painter and
friend of Sargent's. Sargent scholar David McKibbin, who knew the
Barnard sisters, specified that it was painted in 1912 at Abries, in the
French Alps, a few kilometers from the Italian border.
National Atlas of West Nile Virus
Activity
The National Atlas of the United States & CDC have combined to
produce a set of interactive maps, with detail down to county level, to
be updated weekly, showing WNV activity
West Nile Virus: Links to City and State
Websites
Links to public health department information about WNV.
West Nile
Virus
Resources
Contains a list of publications and guidelines from CDC for surveillance
and control of WNV. It also includes information about animals and
poultry from the Department of Agriculture and wildlife from the U.S.
Geological Service.
Pesticides and Mosquito
Control
Fact sheets from the Environmental Protection Agency about mosquito
control and effective pesticides.
Information for
Consumers
From the New York Department of Health. Has fact sheets on topics
related to WNV and it's prevention and control and educational materials
(many with links to additional information)
Questions and Answers about West Nile
Virus
From the New York Department of Health. Facts for the public about the
disease, how it is transmitted, and prevention methods.
West Nile Virus Fact
Sheets
From the New York Department of Health. A list of fact sheets for the
general public on a variety of topics such as eliminating mosquitoes,
outdoor workers, various pesticides, personal precautions, and pets.
West Nile Virus
Surveillance
From Health
Canada.
Information about WNV, including information sheets for the general
public.
CLINICIAN
Epidemic/Epizootic West Nile Virus in the United States:
Revised Guidelines for Surveillance, Prevention, and
Control
To assess the implications of the WNV introduction into the U.S. and to
develop a comprehensive national response plan, the Centers for Disease
Control and Prevention (CDC) and the U.S. Department of Agriculture
(USDA) co-sponsored a meeting of arbovirologists, epidemiologists,
laboratorians, vector-control specialists, wildlife biologists, and
state and local health and agriculture officials in Fort Collins,
Colorado, on November 8-9, 1999. As an outgrowth of this meeting,
recommendations for surveillance, prevention and control of WNV in the
U.S.
were developed, published and used in 2000 by federal, state and local
public health officials. A second national meeting, co-sponsored by CDC,
the Association of Public Health Laboratories and other federal and
state organizations was held in Charlotte, North Carolina, on January
31-February 4, 2001, to review year 2000 WNV activity, and evaluate the
outcomes of recommended surveillance, prevention and control activities.
Based on the results of this second meeting, modified Guidelines were
formulated.
West Nile Virus A Reemerging Global
Pathogen
The recognition of WNV in the Western Hemisphere in the summer of 1999
marked the first introduction in recent history of an Old World
flavivirus into the New World. The United
States is not alone, however, in
reporting new or heightened activity in humans and other animals, and
incursions of flaviviruses into new areas are likely to continue through
increasing global commerce and travel. Similar expansion of other
flaviviruses has been documented. Dengue viruses, perhaps the most
important human flaviviral pathogens, have spread from roots in
Asia to all tropical regions. Japanese
encephalitis (JE) virus has recently encroached on the northern shores
of
Australia
and may soon become endemic in that continent. This issue of Emerging Infectious Diseases focuses on current
understanding of the biology, ecology, and epidemiology of
WNV.
Crow Deaths as a Sentinel Surveillance System for West Nile
Virus in the Northeastern United States, 1999
Abstract: In addition to human encephalitis and meningitis cases, the
WNV outbreak in the summer and fall of 1999 in
New York
State resulted in bird deaths
in New York, New
Jersey, and
Connecticut. From August
to December 1999, 295 dead birds were laboratory-confirmed with WNV
infection; 262 (89%) were American Crows (Corvus brachyrhynchos). The
New York State Department of Health received reports of 17,339 dead
birds, including 5,697 (33%) crows; in
Connecticut 1,040 dead
crows were reported. Bird deaths were critical in identifying WNV as the
cause of the human outbreak and defining its geographic and temporal
limits. If established before a WNV outbreak, a surveillance system
based on bird deaths may provide a sensitive method of detecting
WNV.
Serologic Evidence for West Nile Virus Infection in Birds
in the New York City Vicinity during an Outbreak in
1999
Abstract: As part of an investigation of an encephalitis outbreak in New
York City, we sampled 430 birds, representing 18 species in four orders,
during September 13-23, 1999, in Queens and surrounding counties.
Overall, 33% were positive for WNV-neutralizing antibodies, and 0.5%
were positive for St. Louis encephalitis virus-neutralizing antibodies.
By county, Queens had the most seropositive birds
for WNV (50%); species with the greatest seropositivity for WNV (sample
sizes were at least six) were Domestic Goose, Domestic Chicken,
House Sparrow,
Canada Goose, and
Rock Dove. One sampled bird, a captive adult Domestic Goose, showed
signs of illness; WNV infection was confirmed. Our results support the
concept that chickens and House Sparrows are good arbovirus sentinels.
This study also implicates the House Sparrow as an important vertebrate
reservoir host.
West Nile Virus Isolates from Mosquitoes in New York and
New Jersey, 1999
Abstract: An outbreak of encephalitis due to WNV occurred in
New York City and the
surrounding areas during 1999. Mosquitoes were collected as part of a
comprehensive surveillance program implemented to monitor the outbreak.
More than 32,000 mosquitoes representing 24 species were tested, and 15
WNV isolates were obtained. Molecular techniques were used to identify
the species represented in the WNV-positive mosquito pools. Most
isolates were from pools containing Culex pipiens mosquitoes, but
several pools contained two or more Culex species.
Dead Bird Surveillance as an Early Warning System for West
Nile Virus
Abstract: As part of WNV surveillance in New
York State in
2000, 71,332 ill or dead birds were reported; 17,571 (24.6%) of these
were American Crows. Of 3,976 dead birds tested, 1,263 (31.8%) were
positive for WNV. Viral activity was first confirmed in 60 of the
state's 62 counties with WNV-positive dead birds. Pathologic findings
compatible with WNV were seen in 1,576 birds (39.6% of those tested), of
which 832 (52.8%) were positive for WNV. Dead crow reports preceded
confirmation of viral activity by several months, and WNV-positive birds
were found >3 months before the onset of human cases. Dead bird
surveillance appears to be valuable for early detection of WNV and for
guiding public education and mosquito control efforts.
West Nile Virus Surveillance in Connecticut in 2000 An
Intense Epizootic without High Risk for Severe Human
Disease
Abstract: In 1999,
Connecticut was one of
three states in which WNV actively circulated prior to its recognition.
In 2000, prospective surveillance was established, including monitoring
bird deaths, testing dead crows, trapping and testing mosquitoes,
testing horses and hospitalized humans with neurologic illness, and
conducting a human seroprevalence survey. WNV was first detected in a
dead crow found on July 5 in
Fairfield
County. Ultimately, 1,095
dead crows, 14 mosquito pools, 7 horses, and one mildly symptomatic
person were documented with WNV infection. None of 86 hospitalized
persons with neurologic illness (meningitis, encephalitis,
Guillain-Barré-like syndrome) and no person in the seroprevalence
survey were infected. Spraying in response to positive surveillance
findings was minimal. An intense epizootic of WNV can occur without
having an outbreak of severe human disease in the absence of emergency
adult mosquito management.
Mosquito Surveillance and Polymerase Chain Reaction
Detection of West Nile Virus, New York State
Abstract: WNV was detected in the metropolitan New York City (NYC) area
during the summer and fall of 1999. Sixty-two human cases, 7 fatal, were
documented. The New York State Department of Health initiated a
departmental effort to implement a statewide mosquito and virus
surveillance system. During the 2000 arbovirus surveillance season, we
collected 317,676 mosquitoes, submitted 9,952 pools for virus testing,
and detected 363 WNV-positive pools by polymerase chain reaction (PCR).
Eight species of mosquitoes were found infected. Our mosquito
surveillance system complemented other surveillance systems in the state
to identify relative risk for human exposure to WNV. PCR WNV-positive
mosquitoes were detected in NYC and six counties in the lower
Hudson River
Valley and metropolitan NYC
area. Collective surveillance activities suggest that WNV can disperse
throughout the state and may impact local health jurisdictions in the
state in future years.
Partial Genetic Characterization of West Nile Virus
Strains, New York State, 2000
Abstract: We analyzed nucleotide sequences from the envelope gene of 11
WNV strains collected in New York State during the 2000 transmission
season to determine whether they differed genetically from each other
and from the initial strain isolated in 1999. The complete envelope
genes of these strains were amplified by reverse
transcription-polymerase chain reaction. The resulting sequences were
aligned, the genetic distances were computed, and a phylogenetic tree
was constructed. Ten (0.7%) of 1,503 positions in the envelope gene were
polymorphic in one or more sequences. The genetic distances were 0.003
or less. WNV strains circulating in 2000 were homogeneous with respect
to one another and to a strain isolated in 1999.
Clinical Findings of West Nile Virus Infection in
Hospitalized Patients, New York and New Jersey, 2000
Abstract: Outbreaks of WNV occurred in the New
York metropolitan area in 1999 and 2000.
Nineteen patients diagnosed with WN infection were hospitalized in
New York and
New Jersey in 2000 and
were included in this review. Eleven patients had encephalitis or
meningoencephalitis, and eight had meningitis alone. Ages of patients
ranged from 36 to 87 years (median 63 years). Fever and neurologic and
gastrointestinal symptoms predominated. Severe muscle weakness on
neurologic examination was found in three patients. Age was associated
with disease severity. Hospitalized cases and deaths were lower in 2000
than in 1999, although the case-fatality rate was unchanged. Clinicians
in the Northeast should maintain a high level of suspicion during the
summer when evaluating older patients with febrile illnesses and
neurologic symptoms, especially if associated with gastrointestinal
complaints or muscle weakness.
West Nile Encephalitis in Israel, 1999 The New York
Connection
Abstract: We describe two cases of WNV encephalitis in a married couple
in Tel Aviv,
Israel,
in 1999. Reverse transcription-polymerase chain reaction performed on a
brain specimen from the husband detected a WN viral strain nearly
identical to avian strains recovered in Israel in 1998 (99.9% genomic
sequence homology) and in New York in 1999 (99.8%). This result supports
the hypothesis that the 1999 WNV epidemic in the
United
States originated from the introduction
of a strain that had been circulating in
Israel.
Dead Crow Densities and Human Cases of West Nile Virus, New
York State, 2000
Abstract: In 2000, Staten Island,
New York, reported 10 human WNV cases
and high densities of dead crows. Surrounding counties with <2 human
cases had moderate dead crow densities, and upstate counties with no
human cases had low dead crow densities. Monitoring such densities may
be helpful because this factor may be determined without the delays
associated with specimen collection and testing.
Equine West Nile Encephalitis, United
States
Abstract: After the 1999 outbreak of WNV encephalitis in
New York horses, a case
definition was developed that specified the clinical signs, coupled with
laboratory test results, required to classify cases of WN encephalitis
in equines as either probable or confirmed. In 2000, 60 horses from
seven states met the criteria for a confirmed case. The cumulative
experience from clinical observations and diagnostic testing during the
1999 and 2000 outbreaks of WN encephalitis in horses will contribute to
further refinement of diagnostic criteria.
Mosquito Surveillance for West Nile Virus in Connecticut,
2000 Isolation from Culex pipiens, Cx. restuans, Cx. salinarius, and
Culiseta melanura
Abstract: Fourteen isolations of WNV were obtained from four mosquito
species (Culex pipiens [5], Cx. restuans [4], Cx. salinarius [2], and
Culiseta melanura [3]) in statewide surveillance conducted from June
through October 2000. Most isolates were obtained from mosquitoes
collected in densely populated residential locales in
Fairfield and
New Haven counties, where
the highest rates of dead crow sightings were reported and where WNV was
detected in 1999. Minimum field infection rates per 1,000 mosquitoes
ranged from 0.5 to 1.8 (county based) and from 1.3 to 76.9 (site
specific). Cx. restuans appears to be important in initiating WNV
transmission among birds in early summer; Cx. pipiens appears to play a
greater role in amplifying virus later in the season. Cs. melanura could
be important in the circulation of WNV among birds in sylvan
environments; Cx. salinarius is a suspected vector of WNV to humans and
horses.
Clinical Characteristics of the West Nile Fever Outbreak,
Israel, 2000
Abstract: WNV is endemic in
Israel.
The last reported outbreak had occurred in 1981. From August to October
2000, a large-scale epidemic of WN fever occurred in
Israel;
417 cases were confirmed, with 326 hospitalizations. The main clinical
presentations were encephalitis (57.9%), febrile disease (24.4%), and
meningitis (15.9%). Within the study group, 33 (14.1%) hospitalized
patients died. Mortality was higher among patients >70 years (29.3%).
On multivariate regressional analysis, independent predictors of death
were age >70 years (odds ratio [OR] 7.7), change in level of
consciousness (OR 9.0), and anemia (OR 2.7). In contrast to prior
reports, WN fever appears to be a severe illness with high rate of
central nervous system involvement and a particularly grim outcome in
the elderly.
West Nile Virus Infection in Birds and Mosquitoes, New York
State, 2000
Abstract: WNV was found throughout New
York State in
2000, with the epicenter in New York
City and surrounding counties. We tested 3,403
dead birds and 9,954 mosquito pools for WNV during the transmission
season. Sixty-three avian species, representing 30 families and 14
orders, tested positive for WNV. The highest proportion of dead birds
that tested positive for WNV was in American Crows in the epicenter (67%
positive, n=907). Eight mosquito species, representing four genera, were
positive for WNV. The minimum infection rate per 1,000 mosquitoes (MIR)
was highest for Culex pipiens in the epicenter: 3.53 for the entire
season and 7.49 for the peak week of August 13. Staten
Island had the highest MIR (11.42 for Cx. pipiens), which
was associated with the highest proportion of dead American Crows that
tested positive for WNV (92%, n=48) and the highest number of human
cases (n=10).
West Nile Fever Outbreak, Israel, 2000 Epidemiologic
Aspects
Abstract: From August 1 to October 31, 2000, 417 cases of WNV fever were
serologically confirmed throughout
Israel;
326 (78%) were hospitalized patients. Cases were distributed throughout
the country; the highest incidence was in central
Israel,
the most populated part. Men and women were equally affected, and their
mean age was 54±23.8 years (range 6 months to 95 years). Incidence
per 1,000 population increased from 0.01 in the 1st decade of life to
0.87 in the 9th decade. There were 35 deaths (case-fatality rate 8.4%),
all in patients >50 years of age. Age-specific case-fatality rate
increased with age. Central nervous system involvement occurred in 170
(73%) of 233 hospitalized patients. The countrywide spread, number of
hospitalizations, severity of the disease, and high death rate contrast
with previously reported outbreaks in
Israel.
West Nile Outbreak in Horses in Southern France, 2000 The
Return after 35 Years
Abstract: On September 6,
2000, two cases of equine encephalitis caused by WNV were
reported in southern
France
(Hérault
Province), near
Camargue
National Park, where a WN
outbreak occurred in 1962. Through November 30, 76 cases were laboratory confirmed
among 131 equines with neurologic disorders. The last confirmed case was
on November 3, 2000.
All but three cases were located in a region nicknamed "la petite
Camargue," which has several large marshes, numerous colonies of
migratory and resident birds, and large mosquito populations. No human
case has been confirmed among clinically suspected patients, nor have
abnormal deaths of birds been reported. A serosurvey has been undertaken
in horses in the infected area, and other studies are in progress.
The Relationships between West Nile and Kunjin
Viruses
Abstract: Until recently, WN and Kunjin (KUN) viruses were classified as
distinct types in the Flavivirus genus. However, genetic and antigenic
studies on isolates of these two viruses indicate that the relationship
between them is more complex. To better define this relationship, we
performed sequence analyses on 32 isolates of KUN virus and 28 isolates
of WNV from different geographic areas, including a WN isolate from the
recent outbreak in New
York. Sequence comparisons showed that the KUN
virus isolates from
Australia
were tightly grouped but that the WNV isolates exhibited substantial
divergence and could be differentiated into four distinct groups. KUN
virus isolates from
Australia
were antigenically homologous and distinct from the WN isolates and a
Malaysian KUN virus. Our results suggest that KUN and WNVes comprise a
group of closely related viruses that can be differentiated into
subgroups on the basis of genetic and antigenic analyses.
Rapid Determination of HLA B07 Ligands from the West Nile
Virus NY99 Genome
Abstract: Defined T cell epitopes for WNV may be useful for developing
subunit vaccines against WNV infection and diagnostic reagents to detect
WNV-specific immune response. We applied a bioinformatics (EpiMatrix)
approach to search the WNV NY99 genome for HLA B*07 restricted cytotoxic
T cell (CTL) epitopes. Ninety-five of 3,433 WNV peptides scored above a
predetermined cutoff, suggesting that these would be likely to bind to
HLA B*07 and would also be likely candidate CTL epitopes. Compared with
other methods for genome mapping, derivation of these ligands was rapid
and inexpensive. Major histocompatibility complex ligands identified by
this method may be used to screen T cells from WNV-exposed persons for
cell-mediated response to WNV or to develop diagnostic reagents for
immunopathogenesis studies and epidemiologic surveillance.
West Nile Virus Infection in the Golden Hamster
(Mesocricetus auratus) A Model for West Nile
Encephalitis
Abstract: This report describes a new hamster model for WNV
encephalitis. Following intraperitoneal inoculation of a
New York isolate of WNV,
hamsters had moderate viremia of 5 to 6 days in duration, followed by
the development of humoral antibodies. Encephalitic symptoms began 6
days after infection; about half the animals died between the seventh
and 14th days. The appearance of viral antigen in the brain and neuronal
degeneration also began on the sixth day. WNV was cultured from the
brains of convalescent hamsters up to 53 days after initial infection,
suggesting that persistent virus infection occurs. Hamsters offer an
inexpensive model for studying the pathogenesis and treatment of WNV
encephalitis.
West Nile Virus Infection In Mosquitoes, Birds, Horses and
Humans, Staten Island, New York, 2000
Abstract: WNV transmission in the United
States during 2000 was most intense on
Staten Island, New
York, where 10 neurologic illnesses among humans
and 2 among horses occurred. WNV was isolated from Aedes vexans, Culex
pipiens, Cx. salinarius, Ochlerotatus triseriatus, and Psorophora ferox,
and WN viral RNA was detected in Anopheles punctipennis. An elevated
weekly minimum infection rate (MIR) for Cx. pipiens and increased dead
bird density were present for 2 weeks before the first human illness
occurred. Increasing mosquito MIRs and dead bird densities in an area
may be indicators of an increasing risk for human infections. A
transmission model is proposed involving Cx. pipiens and Cx. restuans as
the primary enzootic and epizootic vectors among birds, Cx. salinarius
as the primary bridge vector for humans, and Aedes/Ochlerotatus spp. as
bridge vectors for equine infection.
Experimental Infection of Chickens as Candidate Sentinels
for West Nile Virus
Abstract: We evaluated the susceptibility, duration and intensity of
viremia, and serologic responses of chickens to WNV (WNV-NY99) infection
by needle, mosquito, or oral inoculation. None of 21 infected chickens
developed clinical disease, and all these developed neutralizing
antibodies. Although viremias were detectable in all but one chicken,
the magnitude (mean peak viremia <104 PFU/mL) was deemed insufficient
to infect vector mosquitoes. WNV-NY99 was detected in cloacal and/or
throat swabs from 13 of these chickens, and direct transmission of
WNV-NY99 between chickens occurred once (in 16 trials), from a
needle-inoculated bird. Nine chickens that ingested WNV-NY99 failed to
become infected. The domestic chickens in this study were susceptible to
WNV infection, developed detectable antibodies, survived infection, and
with one exception failed to infect cage mates. These are all considered
positive attributes of a sentinel species for WNV surveillance
programs.
Widespread West Nile Virus Activity, Eastern United States,
2000
Abstract: In 1999, the U.S. WNV epidemic was preceded by widespread
reports of avian deaths. In 2000, ArboNET, a cooperative WNV
surveillance system, was implemented to monitor the sentinel epizootic
that precedes human infection. This report summarizes 2000 surveillance
data, documents widespread virus activity in 2000, and demonstrates the
utility of monitoring virus activity in animals to identify human risk
for infection.
Exposure of Domestic Mammals to West Nile Virus during an
Outbreak of Human Encephalitis, New York City, 1999
Abstract: We evaluated WNV seroprevalence in healthy horses, dogs, and
cats in New York City after an outbreak of human WNV encephalitis in
1999. Two (3%) of 73 horses, 10 (5%) of 189 dogs, and none of 12 cats
tested positive for WNV- neutralizing antibodies. Domestic mammals
should be evaluated as sentinels for local WNV activity and predictors
of the infection in humans.
Detection of North American West Nile Virus in Animal
Tissue by a Reverse Transcription-Nested Polymerase Chain Reaction
Assay
Abstract: A traditional single-stage reverse transcription-polymerase
chain reaction (RT-PCR) procedure is effective in determining WNV in
avian tissue and infected cell cultures. However, the procedure lacks
the sensitivity to detect WNV in equine tissue. We describe an RT-nested
PCR (RT-nPCR) procedure that identifies the North American strain of WNV
directly in equine and avian tissues.
West Nile Virus in Overwintering Culex Mosquitoes, New York
City, 2000
Abstract: After the 1999 WNV encephalitis outbreak in
New York, 2,300
overwintering adult mosquitoes were tested for WNV by cell culture and
reverse transcriptase-polymerase chain reaction. WN viral RNA and live
virus were found in pools of Culex mosquitoes. Persistence in
overwintering Cx. pipiens may be important in the maintenance of WNV in
the northeastern United
States.
West Nile Virus Outbreak Among Horses in New York State,
1999 and 2000
Abstract: WNV was identified in the Western
Hemisphere in 1999. Along with human encephalitis cases, 20
equine cases of WNV were detected in 1999 and 23 equine cases in 2000 in
New York. During both
years, the equine cases occurred after human cases in
New York had been
identified.
Isolation and Characterization of West Nile Virus from the
Blood of Viremic Patients During the 2000 Outbreak in
Israel
Abstract: We report the isolation of WNV from four patient serum samples
submitted for diagnosis during an outbreak of WN fever in Israel in
2000. Sequencing and phylogenetic analysis revealed two lineages, one
closely related to a 1999 New
York isolate and the other to a 1999 Russian
isolate.
Fatal Encephalitis and Myocarditis in Young Domestic Geese
(Anser anser domesticus) Caused by West Nile Virus
Abstract: During 1999 and 2000, a disease outbreak of WNV occurred in
humans, horses, and wild and zoological birds in the northeastern
USA. In
our experiments, WNV infection of young domestic geese (Anser anser
domesticus) caused depression, weight loss, torticollis, opisthotonus,
and death with accompanying encephalitis and myocarditis. Based on this
experimental study and a field outbreak in
Israel,
WNV is a disease threat to young goslings and viremia levels are
potentially sufficient to infect mosquitoes and transmit WNV to other
animal species.
Comparative West Nile Virus Detection in Organs of
Naturally Infected American Crows (Corvus
brachyrhynchos)
Abstract: Widespread deaths of American Crows (Corvus brachyrhynchos)
were associated with the 1999 outbreak of WNV in the
New York City region. We
compared six organs from 20 crow carcasses as targets for WNV detection.
Half the carcasses had at least one positive test result for WNV
infection. The brain was the most sensitive target organ; it was the
only positive organ for three of the positive crows. The sensitivity of
crow organs as targets for WNV detection makes crow death useful for WNV
surveillance.
Identification of Arboviruses and Certain Rodent-Borne
Viruses Reevaluation of the Paradigm (Commentary)
Diagnostic and epidemiologic virology laboratories have in large part
traded conventional techniques of virus detection and identification for
more rapid, novel, and sensitive molecular methods. By doing so, useful
phenotypic characteristics are not being determined. We feel that the
impact of this shift in emphasis has impaired studies of the biology of
viruses. This position paper is a plea to the scientific and
administrative communities to reconsider the importance of such
information. We also suggest a revised paradigm for virus isolation and
characterization and provide a rationale for accumulating biologic
(phenotypic) information.
Treatment of West Nile Virus Encephalitis with Intravenous
Immunoglobulin (Letter)
WNV is endemic in
Israel.
The overwhelming majority of infections are mild and asymptomatic, but
there have been periodic symptomatic outbreaks. In August 2000, an
epidemic of WNV broke out in
Israel,
with >260 confirmed cases and 20 deaths by the end of September 2000.
Hitherto, the only treatment for this condition has been supportive with
no proven in vivo specific therapy, although ribavirin has shown promise
in in vitro studies. We report an apparent dramatic response to
intravenous immunoglobulin in an immunosuppressed patient and suggest
that this was the result of specific antibodies in the Israeli
immunoglobulin used.
| brain,encephalitis,west nile,west nile virus,wnv,abnormal,abries,absence,abstract,accompanying,accumulating,active,activities,activity,administrative,adult,adult mosquitoes,aedes vexans,aedes/ochlerotatus spp,africa,age,age-specific,ages,agriculture,airwa |
|
|
|
