Deadly NY Virus
Remains Major Mystery
By Donald Sutherland

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.
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.
"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.
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.
House mosquitoes like this have been found with the virus. (Photo courtesy CDC)
An intensive hunt is now on involving legions of researchers across the country who are pursuing answers to the basic questions about this virus.
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.
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).
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.
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.
Currently, there is no known vaccine for West Nile Virus.
"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.
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.
None of the scientific research teams are reviewing the possibility that the disease could have been released from a laboratory in the area.
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.
"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.
"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."
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.
Transmission cycle of the West Nile-like virus (Diagram courtesy CDC)
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.
"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.
"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.
"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.
Treehole mosquito (Photo courtesy CDC)
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.
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.
"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.
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.
"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.
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.
© < Environment News Service (ENS) 1999. All Rights Reserved.