We showed that, compared to IFN-λ4-Null children, children with genetic ability to produce IFN-λ4, and especially those producing functionally strong IFN-λ4-P70 protein, were more likely to experience gastrointestinal infections, manifested by diarrhea, with the first infection episode occurring at a younger age. The gene discussed is IFNL4; the disease is digestive system infectious disorder.