ACE2 is widely expressed in airway epithelium, lung parenchyma, vasculature, kidney, heart, and the gastrointestinal tract [48, 49], primary sites of infection by SARS-CoV and SARS-CoV-2; however, it is interesting to note that ACE2-expressing endothelial cells and human intestinal cells were unaffected by SARS-CoV [50, 51], while ACE2 negative hepatocytes were susceptible to SARS-CoV infection [32]. Here, ACE2 is linked to severe acute respiratory syndrome.