Both of these drugs have a serious flaw for a drug that would be used to eliminate infection and block transmission in people who are not themselves acutely sick with malaria—they cause hemolysis (destruction of red blood cells leading to anemia) in individuals with glucose-6-phosphate dehydrogenase (G6PD) deficiency, a red cell polymorphism that is common in tropical populations because it is associated with some degree of protection against malaria illness [32]. The gene discussed is G6PD; the disease is malaria.