There have been 12 confirmed cases of St. Louis encephalitis in New York City since late August. Three were fatal, all involving elderly victims.
Westchester County Executive Andrew Spano said Tuesday that an 80-year-old Yonkers man has the disease. Two victims were confirmed a day earlier and another person likely has the virus. All are recovering.
Connecticut officials identified the virus in mosquitoes trapped on a Greenwich golf course and in a crow's brain found in Westport. There have been no reported cases in humans in Connecticut.
Officials planned to spray both locations with insecticides Thursday.
In New York, the pesticide malathion has been used. Mayor Rudolph Giuliani defended that choice Tuesday after Westchester officials said they would use a less toxic substance known as Anvil.
"I think this is more a reaction to public relations than it is science," Giuliani said. "Both substances are safe. There may be certain applications of one that are better than the other, but both are equally safe."
Westchester's spraying will be done by helicopter over the southern third of the county, which includes the cities of Yonkers, Mount Vernon, New Rochelle, Port Chester and most of White Plains.
Spraying in Connecticut will be conducted by truck, using resmithrin.
St. Louis encephalitis can cause seizures, paralysis and swelling of the brain. It can be fatal, especially to infants, the elderly and people with immune deficiencies. Its symptoms include fever, headache and lethargy. Humans are infected through mosquito bites.