ACE2 and infection: The organs with high ACE2-expressing cells should be considered a potential high risk for 2019-nCoV infection [ 15]. ACE2 cells are abundantly present in type II alveolar cells (AT2) of lung [ 15], esophagus upper and stratified epithelial cells, absorptive enterocytes from the ileum, and colon [ 16], cholangiocytes [ 17], myocardial cells, kidney proximal tubule cells, and bladder urothelial ells [ 15]. Although COVID-19 infection hardly presented oral symptoms, the ACE2 expression in the oral cavity indicated that the oral infection route of SARS-CoV-2 could not be excluded.