Information on St. Louis Encephalitis
SLE is a viral disease; antibiotics are not effective for treatment and no effective antiviral drugs have yet been discovered. Treatment is supportive.
SLE is the most common mosquito-transmitted human pathogen in the U.S. While periodic SLE epidemics have occurred only in the Midwest and southeast, SLE virus is distributed throughout the lower 48 states. A locally-acquired case of SLE has never been reported in New York City. Since 1964, there have been 4,437 confirmed cases of SLE nation-wide, with an average of 193 cases per year (range 4 - 1,967). However, less than 1% of SLE viral infections are clinically apparent and the vast majority of infections remain undiagnosed.
The incubation period is 5-15 days. Illness ranges in severity from a simple febrile headache to meningoencephalitis, with an overall case-fatality ratio of 5-15 %. The disease is generally milder in children than in adults, but in those children who do have disease, there is a high rate of encephalitis. The elderly are at highest risk for severe disease and death. During the summer season, SLE virus is maintained in a mosquito-bird-mosquito cycle, with periodic amplification by peri-domestic birds and Culex mosquitoes.
SLE can be prevented in two ways: personal protective measures and public health measures to reduce the population of infected mosquitoes. Personal measures include reducing time outdoors particularly in early evening hours, wearing long pants and long sleeved shirts and applying mosquito repellent to exposed skin areas. New York City has arranged for the spraying of insecticides to kill juvenile (larvae) and adult mosquitoes in the neighborhoods where disease has been clustered. There is no commercially available human vaccine for SLE.
See Arboviral Infection for more information
February 2000
