DHFR and infection: The haplotypes based on the single nucleotide polymorphisms at codon 50/51, 59 and 108 of the P. falciparum dhfr gene, and codon 436/437, 540, 581 and 613 of the P. falciparum dhps gene, were determined on day 0 for parasite infections in patients receiving SP (Table 2).