In a restricted setting, this same trend had been reported in 2007 in a tertiary center in Manaus.37 Reasons for this change are not clear and could be related to infection-related complications, as P. vivax is recognizably associated with severe disease,38,39 concurrent infections,40 or treatment-related complications, as primaquine is given without assessment of glucose-6-phosphate dehydrogenase (G6PD) deficiency status, a topic that is currently under investigation. The gene discussed is G6PD; the disease is infection.