Virus Transmission

Although other mosquitoes in the subgenus Stegomyia, including Aedes albopictus and Ae. polynesiensis, have been implicated as vectors in jungles and rural habitats, and on islands in the South Pacific, Ae. aegypti is the most important dengue vector. Although there is some evidence of sylvatic transmission cycles that include nonhuman primates and vertical transmission from an infected female mosquito to her progeny, the majority of dengue virus transmission is between mosquitoes and human hosts. Horizontal virus transmission begins when a mosquito imbibes viremic human blood. Virus enters and replicates in midgut epithelial cells, disseminates to the hemocoel, and infects secondary target tissues, including the salivary glands. Following replication in salivary gland acinar cells, virus is released into the salivary matrix and can be transmitted the next time the infective mosquito probes its mouthparts into a human host in an attempt to locate blood. Extrinsic incubation in the mosquito requires 10 or more days, depending on the ambient temperature. Once infective, Ae. aegypti can transmit virus each time it probes its mouthparts into a host or imbibes a blood meal. Incubation in the human host typically ranges from 4 to 7 days, after which the person is viremic for ~5 days. Fever subsides in concert with the inability to detect virus in the blood.

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