In a multi-site survey of G6PD deficiency in malaria patients in Cambodia, where G6PD Viangchan predominates (WHO class two but quantitatively similar to G6PD Mahidol), phenotypic severe deficiency (i.e. <10% of population normal) provided stronger protection against P. vivax than P. falciparum infections (OR: O.45; 95% CI, 0.32–0.64) (Khim et al., 2013). The gene discussed is G6PD; the disease is malaria.