Successful disease and treatment outcome in Hepatitis C virus infection (demonstration of a sustained virologic response) is strongly associated with a single nucleotide polymorphism (SNP) in the IFN-λ3 promoter (rs12979860; CC genotype over CT or TT) and higher plasma levels of IFN-λ3 [49],[50]. The gene discussed is IFNL3; the disease is hepatitis C virus infection.