Transmission


The mosquito Aedes aegypti feeding on a human host
Dengue virus is primarily transmitted by Aedes mosquitoes, particularly A. aegypti.[2] These mosquitoes usually live between the latitudes of 35° North and 35° South below an elevation of 1,000 metres (3,300 ft).[2] They typically bite during the day, particularly in the early morning and in the evening.[15][16] Other Aedes species that transmit the disease include A. albopictus, A. polynesiensis and A. scutellaris.[2] Humans are the primary host of the virus,[2][12] but it also circulates in nonhuman primates.[17] An infection can be acquired via a single bite.[18] A female mosquito that takes a blood meal from a person infected with dengue fever becomes itself infected with the virus in the cells lining its gut. About 8–10 days later, the virus spreads to other tissues including the mosquito's salivary glands and is subsequently released into its saliva. The virus seems to have no detrimental effect on the mosquito, which remains infected for life. Aedes aegypti prefers to lay its eggs in artificial water containers, to live in close proximity to humans, and to feed on people rather than other vertebrates.[19]
Dengue can also be transmitted via infected blood products and through organ donation.[20][21] In countries such as Singapore, where dengue is endemic, the risk is estimated to be between 1.6 and 6 per 10,000 transfusions.[22] Vertical transmission (from mother to child) during pregnancy or at birth has been reported.[23] Other person-to-person modes of transmission have also been reported, but are very unusual.[9] The genetic variation in dengue viruses is region specific, suggestive that establishment into new territories is relatively infrequent, despite dengue emerging in new regions in recent decades.[7]