The role of mosquitoes in the natural history of California serogroup viruses.

California (CAL) serogroup viruses are associated with Aedes mosquitoes and small mammals. Transovarial transmission has been demonstrated for most CAL viruses and probably represents a major survival mechanism of the group. Stabilized infections with highly efficient transovarial transmission have been reported for some CAL viruses. This mechanism, combined with venereal transmission of virus from transovarially infected males to uninfected females, may substantially reduce the amount of vertebrate-mediated amplification required to maintain CAL viruses in nature. Infection with CAL viruses may be associated with detrimental effects in the mosquito vector.