Eastern equine encephalitis (EEE) and Western equine encephalitis (WEE) are rare, severe arboviral diseases transmitted to humans by the bite of an infected mosquito. Eastern equine encephalitis virus (EEEV) and Western equine encephalitis virus (WEEV) are in the same family Togaviridae, genus Alphavirus. In the United States, most of EEE and WEE cases occurred respectively in the eastern and western states. Only two cases of EEE have been reported in Wisconsin between 1964 and 2011. Most people infected with EEEV and WEEV have no apparent illness. Symptoms of illness begin with the sudden onset of high fever, chills, headache, nausea, and vomiting. Severe illness includes encephalitis, seizures, and coma.