Third, studies of human populations have revealed correlations between the apolipoprotein E genotype of the human host and the susceptibility to malaria infection; although the ApoE ε3 allele is the most frequent worldwide, the ApoE ε4 allele, which is possibly the ancestral one, has an extremely high frequency in malaria endemic areas, including sub-Saharan Africa and Papua New Guinea [38,39]. The gene discussed is APOE; the disease is malaria.