Including participants of both European and African ancestry, it was shown that the strength of association between hepatitis C treatment efficacy and IFNL3 genotype was comparable in both populations and that the increased prevalence of the unfavorable IFNL3 genotype in Africans explained a large fraction of the differences in treatment responsiveness across groups (The first pharmacogenomics GWAS).25 Here, IFNL3 is linked to hepatitis C virus infection.