There is mounting evidence for a role of the IFN-λ family in the regulation of virus pathogenesis [45], particularly in the case of Hepatitis C infection where a polymorphism in the promoter region of IFN-λ3 (IL-28B; polymorphism rs12979860), which correlates with plasma levels of IFN-λ3 [50], is associated with disease and treatment outcome [49]. This evidence concerns the gene IFNL3 and hepatitis C virus infection.