DEAD BIRDS alerted health officials to a rare African encephalitis virus that recently killed five people and infected about 40 others in the New York area. The West Nile virus is also linked to a Toronto man's death and to birds tested in New Jersey and Connecticut.
Federal experts are testing dead birds from Maryland to Florida, fearing the infection might spread through the fall southern migration. No virus has been found in them so far.
The disease is thought to be transmitted by mosquitoes who bite infected birds and then bite humans. Infected humans can also transmit it back to mosquitoes that bite them. Ticks are another suspected carrier.
This is the first confirmed report of West Nile virus in the Western Hemisphere. Scientists must find out how it develops in this new setting before they can come up with a prevention plan.
Travelers abroad can bring back exotic diseases, such as malaria. But the potential for the spread of West Nile encephalitis in the United States is enhanced by its transmission through common urban birds, such as pigeons and crows.
Several states launched emergency spraying programs. Maryland began spraying three weeks ago in response to a late-season explosion of mosquitoes on the Lower Eastern Shore and Southern Maryland. Airplanes and trucks are misting affected areas with Naled, a stronger chemical than the biological insecticides used in spring.
For now, that seems the only way to control the mosquito outbreak and stop the spread of the virus. Residents can help by cleaning up their properties and covering, draining or removing containers that can hold stagnant water, the breeding ground of mosquitoes.