St. Louis Encephalitis

What is St. Louis encephalitis?

The St. Louis encephalitis virus (SLEV) is transmitted to humans by the bite of an infected mosquito. St. Louis encephalitis (SLE) is a rare disease that is related to the West Nile virus and only a few cases are reported in the United States each year.

Who gets St. Louis encephalitis?

Anyone in an area where the virus is circulating can become infected with SLEV from the bite of an infected mosquito. The risk is highest for people who work or spend a lot of time outside. Older people are at increased risk of having severe disease if they are infected.

How is St. Louis encephalitis spread?

SLEV is transmitted through the bite of an infected mosquito. In Virginia, mosquitoes, like the common house mosquito, become infected by feeding on birds infected with the virus. In rare cases St. Louis Encephalitis can be transmitted in blood transfusions from infected donors. It’s important to note the SLEV does not spread directly from person to person.

What are the symptoms of St. Louis Encephalitis?

Most people infected with SLEV do not have symptoms. Those who do become ill usually have fever, headache, vomiting, and tiredness. Signs and symptoms intensify over a period of several days to a week. Some patients recover after this period. Rarely, people can develop signs of encephalitis, such as seizures, speech problems, paralysis, weakness, double vision, droopy eyelids, and unsteadiness. The disease is generally milder in children than in older adults.

How soon after exposure do symptoms appear?

It takes 4 to 14 days after the bite of an infected mosquito to develop symptoms of SLEV disease.

How is St. Louis encephalitis diagnosed?

Diagnosis of SLEV is primarily based on tests of blood or spinal fluid. These tests typically look for antibodies that the body makes against the viral infection.

What is the treatment for St. Louis encephalitis?

There is no vaccines or medicines to prevent St. Louis encephalitis disease. For serious illnesses caused by SLEV, treatment usually involves supportive care. This means patients might need to go to the hospital, get help with breathing, receive fluids through an IV, and take steps to avoid other infections.

How can St. Louis encephalitis be prevented?

Prevent mosquito bites. There is no vaccine or preventive drug for SLEV.

• Use insect repellent containing DEET, picaridin, IR3535 or oil of lemon eucalyptus on exposed skin and/or clothing. The repellent/insecticide permethrin can be used on clothing to protect through several washes. Always follow the directions on the package.
• Wear long sleeves and pants when weather permits.
• Have secure, intact screens on windows and doors to keep mosquitoes out of the house.
• Eliminate mosquito breeding sites by emptying standing water from containers such as flowerpots, buckets and birdbaths once per week. Drill holes in tire swings so water drains out. Empty children’s wading pools and store on their side after use.

How can I get more information about St. Louis encephalitis?

• If you have concerns about St. Louis encephalitis, contact your healthcare provider.
• Call your local health department. You can find your local health department at vdh.virginia.gov/health-department-locator/.
• Visit the CDC page on St. Louis encephalitis at cdc.gov/sle/about/index.html for more information.