Western Equine Encephalitis virus (WEE virus) is a mosquito-borne virus that primarily affects horses and humans. It belongs to the Togaviridae family and is transmitted through the bite of infected mosquitoes, particularly Culex species. The virus can cause inflammation of the brain, leading to serious neurological symptoms. In humans, WEE virus infection is rare but can result in fever, headache, and in severe cases, encephalitis. Vaccines are available for horses to prevent infection, but there is no specific treatment for humans. Preventive measures include mosquito control and avoiding bites, especially in areas where the virus is known to circulate.