One possibility is a different expression of angiotensin-converting enzyme 2 (ACE-2), which represents the SARS-CoV-2 receptor, and transmembrane protease serine 2 (TMPRSS2), which activates the structural spike protein of SARS-CoV-2 for membrane fusion and enables cell infection (Fig. 1). This evidence concerns the gene TMPRSS2 and infection.