Prophylactic administration of 2 μg IFN-λ1/3 (Yu et al., 2016) 1 d prior to infection or a therapeutic regimen of 3 μg per day for 1 wk starting 1 d after infection efficiently prevented lethal disease progression in adult Ifnar1−/− mice (Fig. 7 A). This evidence concerns the gene IFNL1 and infection.