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- NEW YORK (ENS) - A
viral epidemic never before seen in the Western Hemisphere has struck New
York, and even after several months of investigation health and environmental
professionals are at a loss to say exactly what it is, where it originated,
or how it entered the country.
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- The deadly and mysterious mosquito borne virus has killed
six people in the New York Metropolitan area and stricken hundreds with
symptoms of encephalitis - a swelling of the brain - since its emergence
was first noted in August.
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- "It is really an epidemic," says Dr. Philip
Landrigan, chair of the Department of Community and Preventive Medicine
at Mount Sinai School of Medicine in New York City. "We are finding
there are several hundred cases and this outbreak is still growing,"
he says.
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- Hundreds of American crows have also died from the same
virus. U.S. Centers for Disease Control and Prevention (CDC) has confirmed
the virus in birds in New York City, New York State, Connecticut and New
Jersey. The virus has also been confirmed in mosquitoes in New York City
and Connecticut.
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- House mosquitoes like this have been found with the virus.
(Photo courtesy CDC)
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- An intensive hunt is now on involving legions of researchers
across the country who are pursuing answers to the basic questions about
this virus.
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- At first the virus was believed to be the well known
St. Louis encephalitis. But that theory was discarded when pathologists
at New York City's Bronx Zoo sent autopsy samples from several rare flamingos,
a snowy owl and a cormorant in the zoo's collection that died suddenly
to the U.S. Department of Agriculture (USDA) veterinary lab in Ames, Iowa
for analysis.
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- The samples were then forwarded to the U.S. Centers for
Disease Control and Prevention (CDC) Division of Vector-Borne Infectious
Diseases in Fort Collins, Colorado. Scientists there, along with researchers
at the University of California at Irvine studying human tissue samples,
identified the virus as something very like the West Nile virus (WNV).
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- According to the World Health Organization, humans infected
with the West Nile virus can show little effect or they might experience
an influenza-like illness with fever, headache, muscle weakness and disorientation.
Severe cases, particularly elderly people, can suffer permanent neurological
damage or death.
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- The West Nile virus was first discovered in 1937 in the
African country of Uganda. Outbreaks of the disease occur in western Asia
and Europe. In 1996 a West Nile virus outbreak in Rumania infected over
three hundred people and killed 17, mostly elderly, patients.
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- Currently, there is no known vaccine for West Nile Virus.
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- "Right now there is no vaccine available anywhere
in the world," says David Wilson, a veterinarian with the USDA Emergency
Programs. "That's probably because unlike malaria or other infectious
diseases West Nile virus outbreaks are historically sporadic," he
says.
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- Speculation on how the virus entered the New York Metropolitan
area has so far focused on contaminated birds being flown into the area
and or infected humans flying into the region from southern Russia where
a large West Nile outbreak is currently occurring.
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- None of the scientific research teams are reviewing the
possibility that the disease could have been released from a laboratory
in the area.
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- Located one and a half miles off the northeastern end
of Long Island, New York, the USDA Foreign Animal Disease Diagnostic Laboratory
at Plum Island Animal Disease Center is the only location in the United
States where infectious foreign animal disease agents including encephalitis
virus strains are studied.
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- "I have been at the Center for 10 years, and during
that time, I can say with certainty that WNV was never researched here,"
says Dr. Peter Mason, lead scientist at the USDA Foot-and-Mouth Disease
Research Unit at Plum Island. "Before that time, I am 99.9 percent
sure that it was never worked on," says Mason.
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- "We don't know of any laboratories in the region
which researched the West Nile virus," says Kristine Smith, associate
director for public affairs for the N.Y. Department of Health, "and
at this point in the investigation it has not been on the top of our to
do list."
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- Encephalitis virus research has also been conducted in
laboratories at the Yale School of Medicine in New Haven, Connecticut.
The World Health Organization had their encephalitis research lab at that
facility. Several years ago this research work relocated to Galveston,
Texas. In late September, CDC confirmed that birds and mosquitoes in Connecticut
also have been infected with West Nile-like virus. CDC, in collaboration
with the New York State, New York City and Connecticut health departments,
continues to investigate this outbreak.
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- Transmission cycle of the West Nile-like virus (Diagram
courtesy CDC)
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- So far, U.S. federal government scientists from the Centers
for Disease Control and Prevention coordinating the national response to
identify the virus say it is from the Japanese Encephalitis family with
close genetic similarities to the West Nile virus (anitgenic complex of
the genus Flavivirus, family Flaviviridae). It is being called a "West
Nile-like" virus until research is completed.
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- "We haven't fully characterized the strain yet,"
says Dr. Ian Lipkind, director of Emerging Diseases Laboratory at the University
of California at Irvine. "The genetic sequence of the virus has to
be checked and made valid before a 100 percent identification can be made,"
he says. Health officials have grave concerns the virus will hibernate
over the winter and reemerge in the spring. As a vector borne disease,
the West Nile-like virus is believed to be carried by two mosquito strains.
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- "The house mosquito (Culex pipiens) with a lifetime
limit range of less than one mile and the flood water mosquito (Aedes vexans)
with a range of a little over a mile are the carriers of the West Nile-like
virus being investigated," says Dr. Theodore Andreadis, an encephalitis
and mosquito expert with the Connecticut Agricultural Experiment Station
in New Haven.
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- "There is a concern the virus will be harbored over
the winter when these mosquitoes go into hibernation and reemerge in the
spring," says Dr. Andreadis.
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- Treehole mosquito (Photo courtesy CDC)
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- The treehole (Aedes tarsalis) and salt marsh (Aedes solicitous)
mosquitoes with a lifetime range of forty miles are also being reviewed
as potential carriers of the disease.
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- There are also fears by health authorities the virus
will travel south with migrating birds. Dead American crows testing positive
for the virus have so far been found in Connecticut, Long Island, Westchester
and Rockland Counties in the New York, the New York City metropolitan area,
and New Jersey according to officials monitoring the bird deaths at the
U.S. Geological Survey's National Wildlife Health Center in Madison, Wisconsin.
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- "At this point in the investigation it is hard to
know why American crows are more susceptible to the virus then other birds,"
says Dr. Linda Glaser, a disease specialist for the USGS National Wildlife
Health Center.
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- Researchers say 30 percent of the test positive dead
birds have been found in the New York boroughs of Bronx and Queens - the
epicenter for the outbreak - and the crows can travel 50 to 100 miles in
a ay. "No other states have yet come in with test positive dead crows,
but an interesting new development is apparently other species of birds
with the West Nile like virus tested in New York City can still be healthy
even though they are infected," says Glaser.
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- "Right now we are still trying to get a handle on
this new and exotic threat to the country and to allay peoples fears,"
she says.
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- The director of the CDC, National Center for Infectious
Disease, Dr. James Hughes, says these questions may never be answered.
"One of the compelling questions in this investigation is, 'How did
this virus migrate to the Western Hemisphere, and the United States?' As
interesting as this question may be, the answer may remain elusive - Mother
Nature does not always reveal her secrets," he said.
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Service (ENS) 1999. All Rights Reserved.
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