As with other tissues and organs implicated in COVID-19, ACE2 expression is abundant in the esophagus, gastric mucosa, small intestine, and colon [224] and immunofluorescent staining for viral nucleocapsid proteins of gastrointestinal epithelia, taken during endoscopic examination of a COVID-19 patient, demonstrated that SARS-CoV-2 can invade the epithelia of the stomach, duodenum, and rectum [221]. The gene discussed is ACE2; the disease is COVID-19.