ACE2 and infection: The fatal disease observed in the K18-hACE2 model also precludes its adoption for studies on nonlethal SARS-CoV-2 infections, such as those that lead to successful resolution of the infection or the induction of “long COVID.” Nevertheless, models such as the K18-ACE2 transgenic strain fulfill a valuable role for studying induction of lethal disease following SARS-CoV-2 infection and the efficacy of vaccines or therapeutics to prevent pathology.