• Western Equine Encephalitis



    Western equine encephalitis (WEE) is a virus spread by a bite from an infected mosquito. While WEE is rare, an infection can be serious or fatal.


    WEE is caused by a virus. The virus is passed through the bite of an infected mosquito.

    Risk Factors

    Factors that may increase your chance of WEE include:
    • Living in or visiting the plains regions of western and central United States
    • Doing activities outdoors and not using insect repellent


    Most people with WEE do not have any symptoms.
    If symptoms do occur, they appear within 5-10 days after infection and include:
    • Headache
    • Fever
    • Neck stiffness
    • Chills
    • Fatigue
    • Joint and muscle pain
    • Vomiting
    WEE can lead to more serious, life-threatening symptoms like inflammation of the brain (encephalitis), seizures, and coma . These serious symptoms are more common in infants and older adults.
    Nucleus factsheet image
    Copyright © Nucleus Medical Media, Inc.


    In addition to taking your medical history and doing a physical exam, your doctor will ask you:
    • What kind of symptoms you are experiencing
    • Where you have been living or traveling
    • Whether you have been exposed to mosquitoes
    Your doctor may need to test your bodily fluids. This can be done with:
    • Blood tests
    • Cerebrospinal fluid tests to evaluate the fluid that surrounds the brain and spinal cord
    Imaging tests to evaluate the brain can be done with:


    Because the infection is viral, there is no specific treatment for WEE. Treatment will focus on managing your symptoms and related complications through:
    • IV fluids
    • Antiseizure medications
    • Medications to decrease brain swelling
    • Breathing support—mechanical ventilation


    There is no vaccine for humans. There is a vaccine for horses. Prevention of WEE focuses on controlling mosquitoes and avoiding mosquito bites. Steps you can take to avoid mosquito bites include:
    • Stay inside between dusk and dark, when mosquitoes are most active.
    • Wear long pants and long-sleeved shirts when outside.
    • Use an insect repellent with DEET.
    • Repair screens to prevent mosquitoes from entering the house.
    • Use proper mosquito netting at night. Look for netting treated with insecticide.
    • Remove standing water (such as birdbaths, clogged gutters) to prevent mosquito breeding.


    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

    Healthy Alberta http://www.healthyalberta.com


    Fact sheet: Western equine encephalitis. Centers for Disease Control and Prevention website. Available at: http://www.cdc.gov/ncezid/dvbd. Updated November 7, 2005. Accessed January 4, 2013.

    Meningitis and encephalitis fact sheet. National Institutes of Neurological Disorders and Stroke website. Available at: http://www.ninds.nih.gov/disorders/encephalitis%5Fmeningitis/detail%5Fencephalitis%5Fmeningitis.htm. Updated February 16, 2011. Accessed January 4, 2013.

    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.

    Western equine encephalitis fact sheet. Minnesota Department of Public Health website. Available at: http://www.health.state.mn.us/divs/idepc/diseases/weencephalitis/wee.html. Accessed January 4, 2013.

    10/1/2013 DynaMed Plus Systematic Literature Surveillance http://www.dynamed.com/topics/dmp~AN~T208130/Encephalitis: 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.