Similar to the original Wuhan strain, our clinical isolate, which also contains the D614G mutation in the spike protein [28], showed a dose-dependent increase in morbidity and mortality over nine days, corroborating other studies with the K18-hACE2 mice [16,21,29,30,31,32,33], which exhibit a fatal respiratory infection following intranasal administration of SARS-CoV-2. Here, KRT18 is linked to respiratory tract infectious disorder.