 In order to further understand how the presence of parasitemia may modulate the immune system, we propose to study the effects of treating a portion of adult volunteers with a treatment course of artemetherlumefantrine Coartem at the beginning of the dry season approximately January in Ouelessebougou, Mali to clear parasitemia carriage during the dry season and following them for the next 12 months through an entire dry and wet season. We will enroll 50 blood smear or polymerase chain reaction PCR positive volunteers and distribute them equally into two groups at the beginning of the dry season, those who receive or do not receive antimalarial treatment. These subjects will then be followed monthly throughout the dry and rainy seasons to determine the effect of this treatment on T cell markers of suppressionregulation and the incidence of asymptomatic malaria infection and clinical malaria. We hypothesize that markers of T cell suppressionregulation throughout the dry season will be lower in adults who receive a single pre-emptive treatment with Coartem . 