VEEV is a single-stranded positive-sense RNA alphavirus in the Togaviridae family. Alphaviruses are mosquito-borne pathogens; transmission between species and between individual humans occurs via mosquitos. Thus VEEV is also classified as an arbovirus. Arboviruses replicate in arthropod vectors before transfer to vertebrates. New World alphaviruses-including VEEV, Eastern Equine Encephalitis Virus (EEEV), and Western Equine Encephalitis Virus (WEEV) - are found in the Americas and can cause severe encephalomyelitis. Old World alphaviruses - including chikungunya virus - are found in Europe, Asia, and Africa and typically cause fever and polyarthritis.