Source of drug resistant Plasmodium falciparum in a potential malaria elimination site in Saudi Arabia

► Eight out of nine resistant dhfr haplotypes seen in Saudi Arabia carried double mutations (51I, 108N). ► The major double mutant dhfr haplotype has a close evolutionary relationship to east Africa. ► Parasite migration is a plausible source of this lineage. ► A high level of parasite diversity was seen in Jazan, despite the low transmission levels and adequate access to therapy. ► SP pressure is not enough to offset the recurrent arrival (i.e., gene-flow) of mutant haplotypes from outside.