The arboviral encephalitides comprise several different families of arthropod-borne viruses (arboviruses) that cause encephalitis, an inflammation of the brain tissue in humans and vertebrate animals. They are transmitted from one vertebrate host to another by insects, ticks, or other arthropods. The biology and behavior of the arthropod and vertebrate hosts greatly influence the ecology and epidemiology of these viruses. Surveillance for arboviral encephalitis involves the organized monitoring of levels of virus activity, vector populations, infections in vertebrate hosts, human cases, weather, and other factors to detect or predict changes in the transmission dynamics of the infection.