IFNL3 and hepatitis C virus infection: To identify the potentially causal variant tagged by rs8099917, IL-28B had been previously resequenced in 41 HIV/HCV-coinfected individuals with the four extreme genotype/phenotype combinations: chronic or spontaneously cleared hepatitis C and homozygosity for the protective or risk alleles.3 Candidate causal SNP selection was based on location, frequency among the main haplotype families, and linkage disequilibrium.3 This approach led to the prioritization of four SNPs as prime candidates for causality (Fig. 1A).