Plasmodium falciparum strains harboring dihydrofolate reductase with the I164L mutation are absent in Malawi and Zambia even under antifolate drug pressure.
Ochong E, Bell DJ, Johnson DJ, D'Alessandro U, Mulenga M, Muangnoicharoen S, Van Geertruyden JP, Winstanley PA, Bray PG, Ward SA, et al. Antimicrob Agents Chemother. 2008 Nov; 52(11):3883-8. Epub 2008 Aug 25.