One million dead a year, 500 million with the disease, 2.5 billion people at risk: this is the malaria balance sheet in 2007. The distribution and seriousness of the disease depend on the pathogens and vectors involved, as well as environmental conditions. Of the four parasites (Plasmodium), only P. falciparum kills although the other three cause debilitating disease with regular relapses and recrudescence.
More than fifty species of Anopheles can fulfil the vector role which is essential in transmission of the parasite between human beings. Climatic factors (temperature and rainfall), the environment and biogeographical particularities dictate the distribution of anopheline species and determine transmission rates. This is why it makes sense to talk about the biodiversity of malaria. Today, more than 90 % of deaths from malaria occur in Tropical Africa which is home to only 10% of humanity.
Every 30 seconds a child dies from malaria. This continent harbours the most effective vectors (An. gambiae and An. funestus, in particular) and the climate is highly conducive to transmission of the disease. Severe malaria is also seen in forest foci in Southeast Asia, Papua-New Guinea and the Amazon. In the rest of the tropical and subtropical world, P. vivax and/or P. malariae cause less severe disease.