NYC Fears Encephalitis' Spread

Health workers in helicopters and trucks will spray all of New York City with insecticide to stem a rare outbreak of mosquito-borne encephalitis that has claimed three lives and may be spreading, officials said Thursday.

"The information we received is that there is a possibility that if you don't continue to spray, the whole thing can start up again," Mayor Rudolph Giuliani said of measures to fight the first recorded outbreak of St. Louis Encephalitis in New York City.

At a news conference, Giuliani announced plans to extend the spraying of the insecticide malathion from the boroughs of Queens and the Bronx to all five city boroughs in the coming weeks to kill mosquitoes. Officials said malathion pose no threat to people, pets, or vegetables.

Three people, all of them in their 80s and living in the borough of Queens, have died since the Sept. 2 outbreak of the viral infection that can swell the brain, cause fevers, delirium and weakness. The disease is named after the city where it first appeared in 1933 and is more commonly found in the southeastern United States.

The number of confirmed cases has risen to nine from five this week, and for the first time health officials have confirmed a case in another part of the city, in Brooklyn. But officials said there was no reason for alarm or panic.

New York City Health Commissioner Neal Cohen said 56 other people were waiting for laboratory results from the U.S. Centers for Disease Control and Prevention (CDC) to find out whether they were infected. Earlier, officials said there were 48 suspected cases but eight more were reported Thursday.

The best way to avoid the disease is to avoid mosquitoes, the delivery system for the virus, reports CBS This Morning Health Correspondent Dr. Emily Senay. When a mosquito carrying the virus stings, it infects the person by passing it into the bloodstream.

Symptoms usually show up five to 15 days after a bite from a carrier mosquito and range from a slight fever or headache to high fevers, confusion, and convulsions.

The Health Department advised residents in potentially affected areas to wear long-sleeved shirts, long pants and socks and to use insect repellent when outdoors, especially at dawn and dusk, when mosquitoes are most active.

Killing the mosquito and its larvae, and using repellent to avoid bites are the only ways to prevent the spread of the disease. There is no vaccine for encephalitis, and no standard treatment.

Unlike the more serious Eastern Equine encephalitis, most people recover from the St. Louis strain if infection is caught in time, but the disease can be fatal to those with compromised immune systems, such as the elderly.

Experts warn that the threat of encephalitis will continue until shorter days and cooler temperatures change the mosquito's dietary habits, switching from feeding off humans to eating plant pollen in preparation for winter hibernation.