Vertebrate infection occurs when the infected arthropod takes a blood meal.
The term 'arbovirus' has no taxonomic significance. All arboviral encephalitides are zoonotic, being maintained in complex life cycles involving a nonhuman primary vertebrate host and a primary arthropod vector. These cycles usually remain undetected until humans encroach on a natural focus, or the virus escapes this focus via a secondary vector or vertebrate host as the result of some ecologic change. Many arboviruses that cause encephalitis have a variety of different vertebrate hosts and some are transmitted by more than one vector. Another virus, Powassan, is a minor cause of encephalitis in the northern United States, and is transmitted by ticks.