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.
Factors that may increase your chance of WEE include:
- Living in or visiting the plains regions of western and central US
- 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:
- Nausea and vomiting
- Neck stiffness
- Joint and muscle pain
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.
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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
- Lumbar puncture 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
- 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:
- 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 https://www.cdc.gov
National Institute of Allergy and Infectious Diseases https://www.niaid.nih.gov
About Western equine encephalitis. Minnesota Department of Health website. Available at: http://www.health.state.mn.us/divs/idepc/diseases/weencephalitis/basics.html. Accessed December 7, 2017.
Meningitis and encephalitis information page. National Institutes of Neurological Disorders and Stroke website. Available at: https://www.ninds.nih.gov/Disorders/All-Disorders/Meningitis-and-Encephalitis-Information-Page. Accessed December 7, 2017.
Mosquito avoidance. EBSCO DynaMed Plus website. Available at: https://www.dynamed.com/topics/dmp~AN~T115142/Mosquito-avoidance . Updated November 21, 2016. Accessed December 7, 2017.
- Reviewer: EBSCO Medical Review Board David L. Horn, MD, FACP
- Review Date: 11/2018
- Update Date: 12/20/2014