The ecology of California group viruses

Fifteen viruses have been described as members of the California group of arboviruses; of these, 10 are currently considered to be antigenically distinct viruses, 2 are still under consideration, 2 are now considered synonyms of previously described viruses, and 1 (Bocas virus) is now recognized as a variant of mouse hepatitis virus. Synopses of the natural history of 12 viruses of the California group are presented herein. Viruses considered include California encephalitis (CE), Trivittatus (TVT), Tahyna (TAH), Snowshoe Hare (SSH), Melao (MEL), San Angelo (SA), La Crosse (LAC), Keystone (KEY), Jamestown Canyon (JC), Inkoo (INK), South River and Serra do Navio viruses. Brief mention is also made of Lumbo virus, a synonym of TAH virus, and Jerry Slough, a synonym of JC virus. The general aspects of virus transmission appear to be similar for most viruses of the group. The majority appear to have 2 distinct cycles: a dormant maintenance cycle and an active amplification cycle. Transovarial transmission of virus by certain vector species appears to be one significant means of dormant maintenance. Hibernating infected vectors or vertebrate hosts may perhaps also serve to maintain virus. In the amplification cycle, mosquitoes, primarily of the genus Aedes, apparently serve as principal vectors, and mammals serve as vertebrate hosts. The primary vectors and vertebrate hosts utilized by each virus vary considerably. Man is thought to become involved in some cycles only as an accidental, dead-end host. Clinical disease results from infection by some viruses of the group, and this has been documented for lAC, CE and TAH viruses. Other viruses of the group are suspected of causing human illness as well, but documentation is incomplete.