Eastern equine encephalitis (EEE), western equine encephalitis (WEE) and Venezuelan equine encephalitis (VEE) are caused by Alphaviruses. Birds and rodents are the primary reservoirs, but unvaccinated horses are particularly susceptible and often serve as sentinels. These diseases are zoonotic, infecting humans, and are a public health concern. Eastern equine encephalitis is the most common of the three and is found widely in several regions of the United States (especially in areas of high mosquito populations). Western equine encephalitis occurs infrequently, but circulates in wildlife. Venezuelan equine encephalitis is a Foreign Animal Disease and therefore reportable at both the Federal and State level. It occurs in cycles in Central and South America; and there have been incursions into the United States decades ago.

ELISA assay, for detection of specific antibodies to Equine Encephalitis in equine sera.