The proportion of variance in the risk of severe malaria that could be accounted for by genetic polymorphisms and other factors was estimated, and 5·2% of the total variance in the overall risk of severe malaria was accounted for by polymorphisms in 12 genes: HBB, FREM3, ABO, HBA (HBA1 and HBA2), ATP2B4, LOC727982, ARL14, IL10, RPS6KL1, LPHN2 (ADGRL2), INPP4B, and EMR1 (appendix p 34). The gene discussed is ABO; the disease is malaria.