In contrast, infection of K18-hACE2 mice with an omicron BA.5 isolate (SARS-CoV-2QIMR03) or an omicron XBB isolate (SARS-CoV-2UQ01) resulted in severe weight loss requiring euthanasia in nearly all mice by 4–7 dpi (Figure 1A, BA.5, XBB). Here, KRT18 is linked to infection.