Mechanism of vertical transmission of the dengue virus in mosquitoes.

Both experimental and field data suggest that some tropical mosquito-borne flaviviruses, such as dengue and yellow fever, survive dry seasons by vertical (i.e. transgenerational) transmission in their mosquito hosts. Although vertical transmission of arboviruses in mosquitoes is considered to be transovarial in nature, observations reported here indicate that this is probably not true for dengue virus. Rather, infection of the next generation with this virus apparently takes place when the fully developed egg, enclosed in the chorion, is fertilized at the time of oviposition. In contrast to transovarial transmission, the latter mechanism permits the infection of progeny following a single maternal blood meal.