Alphaviruses: Equine encephalitis and others

Arthropod-borne viruses (arboviruses) are an ecologically defined set of viruses that share a common mode of transmission involving arthropod vectors that transmit to vertebrate hosts. Most are biologically transmitted, requiring replication in both arthropods and vertebrate hosts and transmission between vertebrate animals by the bite of mosquitoes, ticks, sandflies, or midges. The vast majority of arboviruses belong to one of five families: Togaviridae, Flaviviridae, Bunyaviridae, Reoviridae, and Rhabdoviridae. Information on their isolation, morphology, sensitivity to inactivation by chemicals, arthropod vectors, vertebrate hosts, laboratory propagation, serological reactions, geographic distribution, clinical manifestations, and epidemiology is found in the International Catalogue of Arthropod-Borne Viruses, compiled by the American Committee on Arthropod-Borne Viruses. This exhaustive reference source has been used freely in preparing this chapter.