In both hamster and K18-hACE2 mouse models, the ∆3678 infections did not cause significant weight loss or death at the highest tested infection dose [106 PFU for hamsters (Fig. 2b) and 4 × 104 PFU for K18-hACE2 mice (Fig. 4c, g)], whereas the WT virus caused weight loss and death at a much lower infection dose (>4 × 102 PFU for K18-hACE2 mice; Fig. 4b, f). The gene discussed is KRT18; the disease is infection.