Distribution of rare blood group phenotypes selected by malaria in Africa and South East Asia. The location of rare blood group phenotypes lacking glycophorin B (S-s−), having altered glycophorin C (Ge−; Gerbich-negative), Fy (Duffy) blood group–null allele (Fy), Sl(a−) allele of complement receptor 1 (CR1), and the Band 3 mutation causing South East Asian ovalocytosis (SAO) in comparison with the distribution of HbS and HbE alleles.⁷²