Overwintering mechanisms of mosquito-borne arboviruses in temperate climates.

It can be concluded from the data cited that transovarial transmission is a plausible explanation for the overwintering of mosquito-borne bunyaviruses of the California serogroup. Vertical transmission of mosquito-borne flaviviruses could explain the overwintering of this group of viruses, but this is far from having been established. At present, the mechanism by which mosquito-borne alphaviruses pass the winter is obscure.