Further, across a patient population, individuals are likely to harbor different numbers of hypnozoites due to differences in infection risk and a skewed distribution of sporozoite numbers inoculated [6,15,16], use of primaquine for radical cure and CYP2D6 polymorphisms causing treatment failures in some individuals [17], or variation in infection susceptibility [18] (which for example may be due to G6PD deficiency [19]). The gene discussed is CYP2D6; the disease is infection.