It has been shown that malaria is a strongly selective factor for many genotypes (e.g., G6PD deficiency, thalassemia, ABO, Rh, MN, Duffy, secretory types (Ss), human leukocyte antigens (HLA), etc.)[21] Malaria may have variations from different altitudes probably due to change of distribution of mosquitoes across an altitudinal gradient [20]. The gene discussed is ABO; the disease is malaria.