TMPRSS2 and digestive system infectious disorder: Besides GI symptoms experienced by many COVID-19 patients and SARS-CoV-2 RNA detected in feces, the rationale supporting intestinal infection was also based on the high level of expression in the intestines of the main SARS-CoV-2 cellular gateways: angiotensin converting enzyme 2 (ACE2) and transmembrane serine protease 2 (TMPRSS2).