Currently, the hACE2 transgenic mouse model with the cytokeratin 18 (K18) promoter [B6.Cg-Tg(K18-ACE2)2Prlmn/J] is widely used for this purpose, as these mice are susceptible to infection with SARS-CoV-1, Middle Eastern Respiratory Syndrome (MERS)-CoV, and SARS-CoV-2 (8, 10, 11). This evidence concerns the gene KRT18 and infection.