At the present time, malaria is responsible for a million deaths a year, with 500 million reported cases of the disease and 2.5 billion people at risk of contracting it. The distribution and severity of the disease vary with the causative agents, vectors and environment. Of the 4 possible parasites, only P. falciparum causes fatal forms; the three others have debilitating effects related to frequent disease recurrence and reviviscence. More than 50 species of anophele are involved in the obligatory transmission of the parasite from man to man. Climate, environment and biogeography condition the distribution of anophele species and modulate the intensity of transmission. This is what is known as the biodiversity of malaria. At the present time, more than 90% of P. falciparum malaria deaths occur in tropical Africa where only 10% of the world's population lives. A child dies of malaria every 30 seconds. This continent is home to the most effective vectors and the climate favours transmission. Severe cases also arise in the forested areas of South East Asia, New Guinea and the Amazon region. Throughout the rest of the tropical and subtropical world, the disease caused by P. vivax and/or P. malariae is less serious.