Due to the high homology between SARS-CoV-2 and SARS-CoV, the causative agent of the severe acute respiratory syndrome (SARS) pandemic which occurred in 2003 [35], a study used SARS-CoV as a reference to investigate the changes in TMPRSS2 expression in cells or animals infected with SARS-CoV-2. The gene discussed is TMPRSS2; the disease is severe acute respiratory syndrome.