G6PD and malaria: These polymorphisms explain an additional 4.3% of the variation in risk of severe malaria (and 19.2% of the explainable variation) over and above the combined 7.4% accounted for by the HbAS polymorphism (6.3%), α-thalassemia (0.3%), ABO blood group (0.3%), and G6PD (0.5%) genes.