The arboviruses were previously grouped as a family because of their common mode of transmission by arthropods (arthropod-borne viruses). They produce viraemia in their vertebrate hosts, and infect blood-sucking arthropod hosts (mosquitoes, ticks, sandflies and biting midges) during feeding; after replication in the arthropod they are transmitted in the saliva injected during feeding. Many of these virus infections are zoonoses transmitted primarily between vectors and animals. Transovarial transmission in ticks, sandflies and mosquitoes, and transtadial transmission in ticks, are probably important maintenance mechanisms. However, most of the former arboviruses were taxonomically unrelated, and have now been regrouped in related families:
Many of the viruses produce encephalitis, haemorrhagic fever or arthritis in various combinations, which also provided some clinical justification for their former grouping. However, there is no close correlation between taxonomically related viruses and the particular clinical syndromes they produce, and the diseases associated with a particular virus are thus now described under the appropriate individual virus headings.