In contrast to the previous hACE2 Tg mice models, including K18-hACE2, A70, and HFH4-ACE2, although severe diffuse interstitial pneumonia and broad extrapulmonary organ damage were seen [69], similar to that observed in some patients infected SARS-CoV [82–84], these mice did not die by SARS-CoV infection (Table 1). This evidence concerns the gene KRT18 and severe acute respiratory syndrome.