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West Nile Virus Spreading Early and Far

Infection is moving along the Atlantic coast and also heading west, officials say

THURSDAY, July 26, 2001 (HealthDayNews) -- The West Nile virus is spreading rapidly along the Atlantic coast and probably headed West, federal officials say.

The virus, native to Africa, made its first U. S. appearance in the New York City area in 1999, hitting the elderly particularly hard. About 60 people, whose median age was 71, were diagnosed with it that year; seven of them died.

Cases have now been detected in birds, horses and humans up into New England and as far south as Florida, the officials say, and there is every reason to believe that infected mosquitoes and birds are carrying the disease toward the West. Researchers believe the disease could spread wherever its preferred transportation vehicle, the Culex pipens mosquito, calls home.

The first human infection this year was identified in a 73-year-old man from Madison County, Fla., says an article in the Centers for Disease Control and Prevention's Morbidity and Mortality Weekly Report. The virus also infected three horses in Jefferson County, Fla., killing one of them. In addition, infected birds have been identified as far north as Massachusetts and as far south as Florida.

"The findings reported in today's MMWR are not unexpected," says Dr. Stephen Ostroff, a medical epidemiologist with the CDC. "We anticipate that the virus will move into new areas as birds migrate. Our concern has been for a spread down the Atlantic coast, and that is essentially what has happened."

Infected mosquitoes have been found this year in Florida, "the furthest south that the West Nile virus has been found in the United States," says Thomas Gomez, a veterinarian epidemiologist with the Department of Agriculture. "Until now, it was found only as far south as Delaware."

The disease is also making its appearance earlier this season. The man infected in Florida was diagnosed on July 15, whereas human cases during the past two years were reported later in the summer. The three horse infections in Florida reflected "the earliest onset of equine cases in the United States," Gomez says. "In the year 2000, it was Aug. 14."

And there are clear signs of spread to the West, says Kathryn Conver, a wildlife disease specialist with the U. S. Geological Survey. "We are working with 18 states, as far west as Washington, and many other states are doing their own work." There is no treatment for the infection, which causes fatigue, headache, muscle pain and joint pain. An antiviral drug has been tried in a few cases, with no apparent effect.

And the number of reported cases appears to be only a small percentage of actual infections, says a report in the journal The Lancet by Farzad Mostashari and colleagues with the New York City Department of Health. A household survey in 1999 found that 19 of 677 people tested positive for the virus. An extrapolation indicates that about 8,200 New Yorkers were infected with West Nile, with about 1,700 showing fever and other symptoms.

Doctors need to be alert for the virus infection "in the differential diagnosis of unexplained summertime fevers, especially if accompanied by headache, muscle ache and joint pain," says a statement by Mostashari.

Ostroff says the findings emphasize the need for people throughout the Northeast and Southeast to cooperate with authorities tracking the virus' move.

"Monitoring is very much dependent on the public informing local health officials about dead birds. And the ability to minimize any impact on human health is dependent on human cooperation," he says.

For personal protection, he suggest using insect repellents when going outdoors and wearing long sleeves and long pants in areas where mosquito activity is likely.

"Also, people should look around their homes for potential breeding sites for mosquitoes. In the Northeast, many mosquitoes responsible for amplification of the disease live around the home. Look for places where mosquitoes can breed, such as clogged gutters, stagnant bird ponds, upturned trash can lids and flower pots with stagnant water," he says.

What To Do

A West Nile virus primer is offered by the New York City Department of Health, and a guide to activity of other state and local health agencies is available from the Centers for Disease Control and Prevention. Also from the CDC is an overall view of the disease.

Curious to see where the disease is hitting? Check out this map courtesy of the U.S. Geological Survey and other government agencies.

SOURCES: Interviews with Kathryn Conver, wildlife disease specialist, U.S. Geological Survey, Madison, Wis.; Thomas Gomez, DVM, veterinarian epidemiologist, U. S. Department of Agriculture, Atlanta, Ga.; Stephen Ostroff, medical epidemiologist, Centers for Disease Control and Prevention, Atlanta, Ga.; July 27, 2001, Morbidity and Mortality Weekly Report; July 27, 2001, The Lancet
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