SLE strikes about two dozen people a year nationwide, causing a potentially fatal inflammation of the brain. It had never been recorded before in New York City–but with no effective drugs to fight it, local officials were taking no chances. As soon as lab tests returned positive on Sept. 3, they began spraying the city with the pesticide malathion. They distributed free insect repellent at firehouses. And they set up a hot line to handle questions–32,700 in the first week. Still, new patients with symptoms continued to report to hospitals. By Saturday, there were nine confirmed victims, all 58 or older; and three of them had died (including two of Asnis’s first three patients). An additional 89 cases were under investigation citywide. And SLE wasn’t the only mosquito-borne ailment to worry the region. In August, two boys got malaria at summer camp on Long Island; the disease is almost always brought back from abroad, not contracted in the United States.
Officials tried to allay fears over SLE, while urging residents to take reasonable precautions–use repellent, wear long sleeves, stay indoors at dusk. “Even if a person is bitten by an infected mosquito, the chance of developing illness is approximately one in 300,” said a city medical advisory. If symptoms appear at all, they develop five to 15 days after the bite. For most people, the virus causes nothing worse than a headache and fever. But in senior citizens, it can lead to disorientation, paralysis and coma. SLE is fatal in 5 percent to 15 percent of victims, most of them elderly. An additional 10 percent to 15 percent have lasting neurological damage.
Fortunately, SLE does not spread easily–that’s why it’s so rare. “It cannot be passed from person to person, only from infected birds to Culex mosquitoes and from mosquitoes to humans,” says Dr. Roy Campbell of the Centers for Disease Control and Prevention. “It tends to be a mid- to late-summer phenomenon.” But why this summer, with its mosquito-unfriendly drought in much of the East? It turns out that Culex pipiens larvae thrive in the top layers of raw sewage and stagnant ponds, which are still plentiful during dry spells. What they don’t like is fresh rain puddles. Still, that doesn’t explain how the infection first came to New York. The CDC and state biologists have started testing local birds and mosquitoes for clues. Their findings won’t stop the current outbreak, but could one day help take the bite out of SLE.
