MOSQUITOES GET DEADLY

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In the ongoing arms race between mosquitoes and humans, the weapons are well known. The insects attack with their maddening buzz and persistent bites. The humans hit back with sprays, screens and repellent creams. Last week the mosquitoes dipped into their arsenal for a worrisome old weapon: encephalitis.

In alerts issued in central Florida and on New York's Long Island, officials said that the virus causing the deadly brain disease was at large and that nature's most loathed insect was carrying it. Earlier in the month, similar alarms were sounded in several states, including Massachusetts, North Dakota and Georgia.

Local businesses and governments responded quickly. In Orlando, Disney World's Magic Kingdom pulled the drawbridge at least partway up, closing swimming pools and water parks an hour before sunset, when the skeeter dinner bell usually sounds. On Long Island, officials considered similar action, including closing parks until the danger subsides. Though the alert is, so far, more scare than scourge, nobody dismisses it. Says Dr. David Graham, an epidemiologist for New York's Suffolk County: "We want to take precautions."

The medical community has reason to be skittish about the disease. The last encephalitis outbreak in Florida occurred in 1990, and during that brief epidemic, 230 people were infected, 11 fatally. The strain of the virus then--as now--was St. Louis encephalitis, a nasty pathogen that at first causes nothing more serious than flulike symptoms but that eventually may cause fever, coma and occasionally death. The New York strain is the rarer but more dangerous Eastern equine encephalitis, a disease that begins with fever, neck stiffness and headaches and may culminate in a swelling of the brain that claims 30% of victims. No effective treatments are available.

So far, there's no evidence that the mosquito-borne pathogens have left the mosquitoes en masse. In Florida, virus-bearing bugs have been found in eight counties, but only two people are known to have contracted the disease. In New York, there are still no reported cases. Yet where there's viral smoke, there may be fire, and doctors fear trouble. Said Dr. Jahangir Moini, a Florida epidemiologist: "We predict we're going to have an outbreak."

Whether the disease does break out--and how widely it spreads--may depend less on how local governments respond than on the reaction of local citizenry. "The key is to protect yourself," says Tom Skinner of the Centers for Disease Control in Atlanta. "That requires wearing long clothing, using insect repellent and staying indoors in the hours right before and after sunset." Avoiding encephalitis-carrying mosquitoes may be no harder than avoiding their benign kin; the stakes, however, are decidedly higher.

--By Jeffrey Kluger. With reporting by David Bjerklie/New York