Bird migration could spread rare encephalitis strain

The deaths of 20 Bronx Zoo birds were caused by the West Nile virus

September 29, 1999
Web posted at: 2:20 p.m. EDT (1820 GMT)

In this story: 43 people infected in New York Symptoms, risk Mosquito-borne disease Ticks tested, too RELATED STORIES, SITES

NEW YORK (CNN) -- As birds head south for the winter, are they bringing a potentially deadly virus with them?

The investigation into a rare strain of encephalitis that has killed five people in New York is growing, with experts testing dead birds along the East Coast to find out whether the mosquito-borne virus has spread.

The West Nile virus, seen before in Africa, Asia, and Europe, but never before recorded in the Western Hemisphere, could have come to the United States from an infected bird smuggled into the country.

VIDEO CNN's Dr. Steve Salvatore gives background on West Nile virus Windows Media 28K 80K     MESSAGE BOARD Bugs, bugs, bugs     TRANSCRIPT CNN interview with Dr. Gigi El-Bayoumi   How to protect yourself: Dr. Gigi El-Bayoumi, associate professor of internal medicine at George Washington University, recommends taking these precautions against encephalitis and other insect-borne diseases: •Wear long, protective clothing •Stay inside at dusk and dawn, the times when mosquito bites are most likely •Use insect repellents containing the active ingredient DEET •Spray both skin and clothing with the repellent

"The more likely possibility, however, is that somebody with this virus infection stepped off an airplane, attended an outdoor event and was bitten numerous times by mosquitoes," said professor Dickson Despommier of the Columbia University School of Public Health.

As a result, "those mosquitoes became infected," he told CNN.

The virus is transmitted to humans by mosquitoes that have bitten the infected birds.

With winter approaching, infected birds may be migrating to other parts of the country from New York, where 43 people have tested positive for the virus, health officials said.

The St. Louis strain of encephalitis was originally blamed for the outbreak in New York, but the cases were reclassified as the West Nile virus on Tuesday by the Centers for Disease Control and Prevention.

"The odds are good (the West Nile virus) will travel (to the southern United States) via the migratory bird route and into the mosquitoes of those local populations," Despommier told CNN.

So far, the virus has not appeared in any of the dead birds -- mostly crows -- being tested in areas from Maryland to Florida, said Roger Nasci, a CDC entomologist. "This is a developing situation," he said.

One dead bird in Westport, Connecticut, and another in Scarsdale in New York's Westchester County have tested positive for the West Nile virus.

Symptoms of the West Nile virus are similar to those of the St. Louis strain but are generally milder.

For most people, it's "just like any other viral infection -- fever, headache, muscle aches," said Dr. Gigi El-Bayoumi, associate professor of internal medicine at George Washington University.

"You feel under the weather for several days and then, for the most part, you go back to work and you can go back to your usual activities," she told CNN.

It's estimated that "only one in 300 people who are bitten by a mosquito who carries this virus will actually get sick," said Dr. Beth Levine of Columbia Presbyterian Hospital in New York.

In rare cases, though, the virus -- which inflames the brain -- can cause neurological disorders and death. Especially vulnerable are:

•The elderly and young

•Anyone with a weakened immune system

•People with other medical problems, such as diabetes, heart disease or those on dialysis.

New York City, New Jersey and Connecticut have been spraying pesticides to kill mosquitoes.

The virus is transmitted to humans by mosquitoes that have bitten infected birds

The virus is not transmitted from person to person or from birds to people. "It's the virus that infects the mosquitoes that then pass it along to human beings," said El-Bayoumi.

New York Health Commissioner Dr. Antonia Novello said 520 dead birds have turned up from Connecticut to Suffolk County on Long Island. In Suffolk County, officials also are investigating the deaths of several horses.

A total of 162 possible cases are under investigation in New York City.

In Connecticut, the virus has been found in mosquitoes and a dead bird but not in humans.

Late last month, some dead crows were spotted near the Bronx Zoo. Subsequently, 20 zoo birds died -- including an American bald eagle, an owl and five Chilean flamingos -- and tested positive for the African strain.

'My red flag went up' when the zoo birds died, says McNamara

"My red flag went up right away that we were dealing with something very serious and based on my experience as a comparative pathologist, I was very concerned that it was a virus," said Dr. Tracey McNamara, a veterinary pathologist at the zoo.

The zoo said it had not imported any African birds in six months. Any before that had passed standard federal quarantine checks, a spokeswoman said.

Scientists also were testing ticks, which cannot be killed by aerial insecticide spraying like mosquitoes can, to see if they might spread the West Nile virus, the New York Daily News reported.

The scientists fear that the ticks and mosquitoes, which hibernate for winter, could return in the spring and spread the virus.

Ticks have been found infected with West Nile in other countries, said Dr. Duane Gubler of the CDC.

Medical Correspondent Dr. Steve Salvatore, Correspondent Gary Tuchman and The Associated Press contributed to this report, written by Jim Morris.

RELATEDS AT :

West Nile-like virus outbreak confirmed in New York

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RELATED STORIES:

Scientists work to solve mystery of N.Y. insect-borne virus
September 28, 1999
Bird virus blamed for New York encephalitis death
New strain of encephalitis identified in New York birds
Encephalitis outbreak spreads to Manhattan
N.Y. disease outbreak called a global warning
Encephalitis outbreak spreads outside New York City

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RELATED SITES:

Columbia University School of Public Health
Centers for Disease Control and Prevention
George Washington University
CPMCnet, Columbia Presbyterian Medical Center
New York State Department of Health
The Bronx Zoo

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