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.
Factors that may increase your chance of WEE include:
Most people with WEE do not have any symptoms.
If symptoms do occur, they appear within 5-10 days after infection and include:
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.
Copyright © Nucleus Medical Media, Inc.
In addition to taking your medical history and doing a physical exam, your doctor will ask you:
Your doctor may need to test your bodily fluids. This can be done with:
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:
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:
Centers for Disease Control and Prevention
National Institute of Allergy and Infectious Diseases
About Western equine encephalitis. Minnesota Department of Health website. Available at:
...(Click grey area to select URL)
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: http://www.dynamed.com/topics/dmp~AN~T115142/Mosquito-avoidance . Updated November 21, 2016. Accessed December 7, 2017.
Last reviewed November 2018 by
EBSCO Medical Review Board
David L. Horn, MD, FACP
Last Updated: 12/20/2014