Mosquitoes usually pick up the Dengue virus while feeding on the blood of an infected person, the virus incubates for a period of up to 10 days and an infected mosquito is capable, during probing and blood feeding, of transmitting the virus for the rest of its life. It is also suspected that infected female mosquitoes may transmit the virus to their offspring by transovarial (via the eggs) transmission, but how relevant this in sustaining transmission of the virus to humans remains unclear.
So while infected mosquitoes are the culprits in spreading the disease it is infected humans who are the main carriers and multipliers of the virus, as they provide a source for uninfected mosquitoes. The virus circulates in the blood of infected humans for two to seven days and this is when symptoms appear and the Aedes mosquitoes may acquire the virus when they feed on an individual during this period - some research has shown that monkeys in some parts of the world also play a similar role in the transmission of the dengue virus.
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