• St. Louis Encephalitis


    St. Louis encephalitis is a mosquito-borne infection. This disease can affect the central nervous system, causing severe complications and even death.
    The Central Nervous System
    si1210 97870 1 central nervous
    Copyright © Nucleus Medical Media, Inc.


    St. Louis encephalitis is caused by a virus. Mosquitoes are infected with this virus when they feed on birds. Infected mosquitoes can transmit the virus to humans and animals. St. Louis encephalitis is not spread from person to person.

    Risk Factors

    Factors that may increase your chance of St. Louis encephalitis include:
    • Increased age
    • Living in or visiting the southern, central, or western United States, especially during the summer and fall


    St. Louis encephalitis can result in a wide range of symptoms or produce no symptoms at all. The disease can be mild, severe, or even fatal.
    Symptoms usually appear 5-15 days after the bite of an infected mosquito and may include:
    • Headache
    • Fever
    • Neck stiffness
    • Rash
    • Joint pain
    • Stupor
    • Disorientation
    • Coma
    • Tremors
    • Convulsions—especially in infants
    • Paralysis


    Your doctor will ask about your symptoms and medical history. A physical exam will be done. Blood tests will also be done to identify the virus.


    There is no specific treatment for St. Louis encephalitis. Treatment will focus on managing your symptoms and complications, such as through supporting breathing and providing fluids.


    There is no vaccine against St. Louis encephalitis. Prevention of this disease centers on controlling mosquitoes and avoiding mosquito bites. Steps you can take to avoid mosquitoes include:
    • Stay inside between dusk and dark. This is when mosquitoes are most active.
    • Wear long pants and long-sleeved shirts when outside.
    • Spray exposed skin with an insect repellent that contains up to 35% diethyltoluamide (DEET).
    • Use proper mosquito netting at night. Look for netting treated with insecticide.


    Centers for Disease Control and Prevention http://www.cdc.gov

    National Institute of Allergy and Infectious Diseases http://www.niaid.nih.gov


    Health Canada http://www.hc-sc.gc.ca

    Public Health Agency of Canada http://www.phac-aspc.gc.ca


    Reimann CA, Hayes EB, DiGuiseppi C, et al. Epidemiology of neuroinvasive arboviral disease in the United States, 1999-2007. Am J Trop Med Hyg. 2008;79(6):974-979.

    St. Louis encephalitis. EBSCO DynaMed website. Available at: http://www.ebscohost.com/dynamed. Updated July 16, 2012. Accessed January 4, 2013.

    Saint Louis encephalitis fact sheet. Centers for Disease Control and Prevention website. Available at: http://www.cdc.gov/sle. Updated June 11, 2007. Accessed January 4, 2013.

    10/7/2013 DynaMed Systematic Literature Surveillance DynaMed's Systematic Literature Surveillance: Reimer LJ, Thomsen EK, Tisch DJ, et al. Insecticidal bed nets and filariasis transmission in Papua New Guinea. N Eng J Med. 2013;369(8):745-753.

    Revision Information

  • LiveWell personal health survey

    How healthy are you really? Find out – free.Learn more

    It's time to stop guessing. If you want to make some changes but just aren't sure how, the free personal health survey from LiveWell is a great place to start.

  • HeartSHAPE Spotlight

    At risk for a heart attack? Learn more

    Fight heart disease and prevent heart attacks. HeartSHAPE® is a painless, non-invasive test that checks pictures of your heart for early-stage coronary disease.

  • Calories and Energy Needs

    Calorie NeedsLearn more

    How many calories do you need to eat each day to maintain your weight and fuel your physical activity? Enter a few of your stats into this calculator to find out.

  • Ideal Body Weight

    Ideal Body WeightLearn more

    Using body mass index as a reference, this calculator determines your ideal body weight range. All you need to do is enter your height.

  • Body Mass Index

    Body Mass IndexLearn more

    This tool considers your height and weight to assess your weight status.

  • Can we help answer your questions?

    Wellmont Nurse Connection is your resource for valuable health information any time, 24 hours a day, seven days a week. Speak to a Nurse any time, day or night, at (423) 723-6877 or toll-free at 1-877-230-NURSE.