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Malaria is transmitted between people by mosquitoes, and more than 60 species have been incriminated in the transmission of infection. Some species are more significant than others as vectors because of variations in susceptibility to the parasite or the propensity of the mosquito to bite humans and to enter houses when looking for a blood meal. Anopheles gambiae sensu lato is the vector of most significance in Africa.
The local form(s) of the vector are an important determinant of the transmission dynamics of infection. Together with the local climatic conditions, this can have profound effects on how malaria impacts on the human population. In many areas, successive infections with malaria occur repeatedly from birth. This regular exposure leads to the acquisition of a level of immunity against the more severe outcomes of infection. But nature's 'vaccine' is paid for by an unacceptable level of infant and childhood mortality.
Where exposure to infection is more sporadic, the clinical manifestations of malaria are more evenly spread across age-groups and epidemics may occur.
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[WTD023873] Malaria transmission patterns.doc