Countywide : Threat of Encephalitis Believed Over for Year

After weekly spraying of freshwater marshes and stepped-up checks of “sentinel� chicken flocks, officials have reported only one case of mosquito-borne encephalitis in Southern California this summer, allaying fears of an outbreak after 27 people came down with the disease last year.

A Sylmar woman contracted the disease, and tests of mosquitoes in the San Fernando Valley showed positive signs of the virus, according to state officials.

Last year, a Los Angeles woman died, and 26 others in Orange, Los Angeles, Riverside and San Diego counties were affected in the first area cases since 1959.

Chicken flocks at Yorba Linda, UC Irvine and San Clemente were tested regularly for traces of the disease but no positive results were recorded, according to Fred Beams of the Orange County Vector Control District.

In addition, marshes in Irvine and in Newport Beach’s Upper Bay were sprayed weekly, and insecticide pellets were dropped to fight mosquito larvae. The weekly cost of the fight was $2,500, officials said.

Beams said he feels that the threat of an outbreak has ended until next March, adding: “I think if we were going to see any cases, we’d have seen them by now.�

District officials will have to decide whether to continue the spraying next year and whether to continue testing of three flocks rather than the single flock usually maintained at Featherly Park, Beams said.

“That’s something that we’re going to have to take a look at,� he said. “It’s fairly expensive to spray, and we don’t want to waste money. But at the same time, we don’t want another outbreak.�

He said that no accepted theory for the 1984 cases has been found but that a combination of high humidity and warm temperatures that summer were ideal for mosquitoes.