TMPRSS2 and viral infectious disease: According to the currently accepted mechanism of viral infection, both SARS-CoV (also termed SARS-CoV-1) and the related, recently emerged SARS-CoV-2 rely on two membrane-bound host peptidases for entry into target cells: the carboxypeptidase, angiotensin-converting enzyme 2 (ACE2), and a serine proteinase known as TMPRSS2/TMPS2 or epitheliasin.