ABSTRACT
Arboviruses are viruses that are transmitted by arthropods (usually ticks, mosquitoes, or other blood-feeding insects). In fact, “arbo” is derived from the rst two letters of “arthropod” and “borne,” so that arbovirus is a shortened form of arthropod-borne virus. Arboviruses are members of four different families of viruses: Togaviridae, Flaviviridae, Reoviridae, and Bunyaviridae (Table 20.1). More than 500 arboviruses have been recognized worldwide, and at least 5 of them were rst isolated in Canada and 58 in the United States (Calisher 1994). In this chapter, we will discuss several arboviruses of the Togaviridae family that cause human encephalitis in the United States and Canada. These diseases include eastern equine encephalitis (EEE), western equine encephalitis (WEE), and Venezuelan equine encephalitis (VEE). In animals, diseases caused by these same viruses are often referred to as “encephalomyelitis” (inammation of the brain and spinal cord) rather than “encephalitis” (CDC 2005).
