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Bracing for encephalitis

A wet winter combined with a small St. Louis encephalitis outbreak last year point to a possible epidemic of the deadly disease this year, top state health officials warn.

Counties should set up early warning systems with flocks of sentinel chickens, advised state entomologist Jonathan Day and communicable disease director Dr. Gary Hlady.

There is a 50-50 chance of an epidemic similar to the 1990 outbreak, which infected 226 people and killed 11 in Florida, Day said.

The 1990 outbreak shut down nighttime activities in many Florida communities, including Halloween, parades, Christmas tree lightings and school sports.

"We are already halfway to a 1994 epidemic," Day wrote in a paper to health and mosquito experts.

Day said last fall's small outbreak of a form of the disease called St. Louis encephalitis mirrors what happened the year before the 1990 epidemic.

One warning sign still to be determined is the weather, but it doesn't look good, Day said. A wetter-than-normal winter encourages the breeding of mosquitoes, which transmit the disease, he said. South Florida has been about twice as wet as normal this year.

One indicator working against an outbreak is a smaller population of wild birds, which give the disease to mosquitoes, he said.

"The probability is for a large epidemic year," Day said. "Everything is there except for the wild birds."

St. Louis encephalitis can cause such mild symptoms as a headache or dizziness, but also can cause swelling of the brain, paralysis and death.

The disease usually strikes in October and November, Day said. But in big epidemic years, the first cases often are seen in July, he said.

"It's an ongoing concern in Florida," Hlady said. "We try to stay on top of it as best we can."

The sentinel chicken programs work because mosquitoes that carry the disease prefer to bite birds instead of people, Day said. Officials then test the chickens' blood to see if they have antibodies indicating infection.

In the center of an epidemic area, flocks of chickens will get signs of the disease up to six weeks before humans do, Day said. It costs about $15,000 a year to maintain and test the chickens each week.

The state decided in 1988 to cut sentinel chicken programs across Florida, said Willard Galbreath, environmental administrator of the Broward County public health unit.