The absence of clustering of malaria cases suggests the presence of factors other than host genetic polymorphisms [e.g., the protective effect of sickle cell trait and the glucose-6-phosphate dehydrogenase (G-6-PD) deficiency, which is showed to be associated with clinical malaria heterogeneity].47–50 Possibly, housing construction and environmental conditions could influence the risk of infection.47–49. The gene discussed is G6PD; the disease is infection.