What causes St. Louis Encephalitis?
St. Louis encephalitis virus (SLEV), a flavivirus, causes St. Louis encephalitis.
How do people get infected with SLEV?
St. Louis encephalitis is caused by the bite of an infected mosquito, most commonly Culex pipiens and Cx. quinquefasciatus (also Cx. nigripalpus in Florida). The normal infection cycle is between the mosquito and common urban and suburban birds such as robins, blue jays, crows and sparrows. People are considered "dead-end hosts". That is, humans are rarely, if ever, have a high enough concentration of virus to pass the virus back to a mosquito.
What are the symptoms of St. Louis encephalitis?
The symptoms of SLEV infections are similar to those of infections by West Nile virus (WNV) La Crosse encephalitis virus (LACV).
- Many infected people show no symptoms
- Milder symptoms include fever, headache, nausea, vomiting, body aches
- Severe symptoms involve development of encephalitis (inflammation of the brain): severe headache, paralysis, coma
What is the recovery rate for SLEV infections?
Full recovery is common; long-term chronic disability rarely occurs. Between 5% and 30% of SLEV encephalitis patients die from the disease; the mortality rate is highest among the elderly.
How are SLEV infections treated? Is there a vaccine?
There is no vaccine for SLEV encephalitis, and no specific treatment. Treatment is made on a case-by-case basis, depending on the severity of the symptoms.
Who is most at risk?
While anyone in an area where SLEV encephalitis occurs is at risk, older adults are most likely to develop severe symptoms.
Where in the US have SLEV infections occurred?
SLEV encephalitis was first identified in the city of St. Louis, Missouri and in St. Louis County, Missouri in 1933. SLEV encephalitis (neuroinvasive, i.e, the severe form of the disease) has since been reported in 43 states plus Washington, D.C., between 1964 and 2010.
How can I protect myself?
The most effective ways to prevent infection with SLEV is to minimize your exposure to mosquito bites. See the mosquito safety page for more information.
Where can I get more information?
The Centers for Disease Control and Prevention is an excellent source of information. Scientific publications about St. Louis encephalitis can be obtained through PubMed.gov.