🦠microbiology review

Western equine encephalitis (WEE)

Written by the Fiveable Content Team • Last updated September 2025
Written by the Fiveable Content Team • Last updated September 2025

Definition

Western equine encephalitis (WEE) is a mosquito-borne viral infection that affects the central nervous system, primarily in horses and humans. It is caused by the Western equine encephalitis virus (WEEV), an arbovirus of the Togaviridae family.

5 Must Know Facts For Your Next Test

  1. WEE is transmitted to humans and animals through the bite of an infected mosquito, primarily Culex tarsalis.
  2. Symptoms in humans can range from mild flu-like illness to severe neurological damage including encephalitis, which can be fatal.
  3. The virus has an incubation period of 5 to 10 days before symptoms appear.
  4. There is no specific antiviral treatment for WEE; supportive care is the mainstay of therapy.
  5. Vaccination programs exist for horses but there is currently no vaccine available for human use.

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