CYP2D6 and Plasmodium falciparum malaria: CYP2D6 polymorphisms in humans vary by ethnicity and geography [9] and some in the field believe that travellers (up to ~13% in the case of travellers with European ancestry) with an inherited CYP2D6 deficiency may be at greater risk of contracting falciparum malaria if using primaquine for malaria prophylaxis [1, 10].