The potentially deadly coronavirus disease 2019 (COVID-19) that has swept the world over the last 12 months has not affected animals with corresponding severity. In order to understand the mechanism of severe disease, animal models have been used. This includes a mouse model that expresses human angiotensin-converting enzyme 2 (hACE2) under the cytokeratin 18 promoter (K18-hACE2). A new preprint appearing on the bioRxiv* server indicates that this may not be a faithful model of human lethal infection with severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2).
