Identify malaria cases in the Fatick region from an open cohort set up in 1990 for Dielmo and in 1993 for Ndiop. The objectives are as follows: 1- Identify a threshold (level) of parasite carriage which determines the occurrence of malaria and which varies according to the level of transmission of the disease (endemic or seasonal); 2- Evaluate the impact of the introduction of new drugs and impregnated mosquito nets on disease transmission; 3-Monitor the sensitivity of parasites to drugs and mosquitoes to insecticides.