G6PD and G6PD deficiency: Intuitively, we hypothesize that Duffy phenotype and G6PD deficiency have an “opposite” effect in Africa [35,36]: non-black Africans are usually Duffy-positive and the African-type G6PD A– genotype is rarely encountered, while most black Africans are Duffy-negative, some of whom may have G6PD A– genotype.