Although P. vivax has been shown to tolerate temperate regions, its distribution is nevertheless widespread and is present in southeast Asia and Oceania, South and Central America, the Indian subcontinent, eastern Mediterranean and parts of southern Europe, and Africa. Although P. falciparum is more prevalent in Africa than P. vivax, in the other regions of the world populations are, in general, equally likely to be exposed to both species.15 African populations who are Duffy blood group-negative have shown resistance to erythrocyte P. vivax infection demonstrating the importance of the Duffy antigen receptor for invasion of vivax sporozoites. Recent findings in Madagascar, however, have demonstrated now that Duffy-negative and Duffy-positive populations of diverse ethnic backgrounds can both sustain a vivax infection