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Transmission


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 bite primarily during the day.[14] 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][11] but it also circulates in nonhuman primates.[15] An infection can be acquired via a single bite.[16] 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 off people rather than other vertebrates.[17]

Dengue can also be transmitted via infected blood products and through organ donation.[18][19] In countries such as Singapore, where dengue is endemic, the risk is estimated to be between 1.6 and 6 per 10,000 transfusions.[20] Vertical transmission (from mother to child) during pregnancy or at birth has been reported.[21] Other person-to-person modes of transmission have also been reported, but are very unusual.

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Clinical course

The characteristic symptoms of dengue are sudden-onset fever, headache (typically located behind the eyes), muscle and joint pains, and a rash. The alternative name for dengue, "break-bone fever", comes from the associated muscle and joint pains.[1][7] The course of infection is divided into three phases: febrile, critical, and recovery.[8] The febrile phase involves high fever, often over 40 °C (104 °F), and is associated with generalized pain and a headache; this usually lasts two to seven days.[7][8] At this stage, a rash occurs in approximately 50–80% of those with symptoms.[7][9] It occurs in the first or second day of symptoms as flushed skin, or later in the course of illness (days 4–7), as a measles-like rash.[9][10] Some petechiae (small red spots that do not disappear when the skin is pressed, which are caused by broken capillaries) can appear at this point,[8] as may some mild bleeding from the mucous membranes of the mouth and nose.[5][7] The fever itself is cl...
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Signs and symptoms

Typically, people infected with dengue virus are asymptomatic (80%) or only have mild symptoms such as an uncomplicated fever.[1][2][3] Others have more severe illness (5%), and in a small proportion it is life-threatening.[1][3] The incubation period (time between exposure and onset of symptoms) ranges from 3–14 days, but most often it is 4–7 days.[4] Therefore, travelers returning from endemic areas are unlikely to have dengue if fever or other symptoms start more than 14 days after arriving home.[5] Children often experience symptoms similar to those of the common cold and gastroenteritis (vomiting and diarrhea),[6] but are more susceptible to the severe complications
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