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St. Louis Encephalitis


 pdf Version | Information from CDC about St. Louis Encephalitis

What is St. Louis encephalitis?

St. Louis encephalitis (SLE) is closely related to West Nile virus and is transmitted by the same mosquito species.

Who is at risk for SLE?

All residents of areas where active cases have been identified are at risk of getting St. Louis encephalitis. SLE is milder in children than in adults, and elderly persons are much more likely to develop severe neurological disease. Case-fatality rates range from 5% to 15%.

How do people get SLE?

People become infected with SLE from the bite of a mosquito that is infected with the virus. Mosquitoes become infected by feeding on birds infected with SLE. The virus grows both in the infected mosquito and the infected bird, but does not make either one sick. You can not get the virus from other people, birds or insects other than mosquitoes.

What are the symptoms of SLE?

Mild infections occur without apparent symptoms other than fever with headache. More severe infection is marked by headache, high fever, neck stiffness, stupor, disorientation, coma, tremors, occasional convulsions (especially in infants) and mild paralysis.

How many cases of SLE have been reported in Virginia?

SLE was first reported in humans in Virginia in 1975 and a total of 13 cases have been reported in Virginia to date.

How can I help prevent SLE?

1. Wear long, loose and light-colored clothing.

2. If possible, stay indoors when mosquitoes are biting.

3. Use insect repellant with the smallest percentage of DEET necessary for the length of time you are exposed to mosquitoes, follow manufacturer’s directions when using repellants.

4. Turn over or remove containers in your yard where water collects, such as old tires, potted plant trays, buckets and toys.

5. Eliminate standing water on tarps or flat roofs.

6. Clean out birdbaths and wading pools once a week.

7. Clean roof gutters and downspout screens.

Where can I get more information on SLE?

Call your local health department of visit one of the following sites:


Last Updated: 03-29-2013

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