Channel News Asia: [2] While we most commonly associate COVID-19 with fever and cough, gastrointestinal symptoms including diarrhoea, vomiting and abdominal pain are not unheard of in people who contract coronavirus.
[2] This is likely because SARS-CoV-2, the virus that causes COVID-19, is found in the gut as well as the respiratory tract.
[3] Importantly, the gut’s involvement in coronavirus illness points to the possibility COVID-19 could spread through faeces.
[4] At this stage we don’t know for certain whether or not that occurs – but we can take precautions anyway.
[5] SARS-CoV-2 gains entry into human cells by latching onto protein receptors called ACE2, which are found on certain cells’ surfaces.
[6] Around 2 per cent of the cells lining the respiratory tract have ACE2 receptors, while they are also found in the cells lining the blood vessels.
[7] But the greatest numbers of ACE2 receptors are actually found in the cells lining the gut. Around 30 per cent of cells lining the last part of the small intestine (called the ileum) contain ACE2 receptors.
[8] Clinicians have detected coronavirus in tissue taken from the lining of the gut (oesophagus, stomach, small bowel and rectum) through routine procedures such as endoscopy and colonoscopy, where we use cameras to look inside the body. They found abundant ACE2 receptors in those tissue samples.

While some researchers have proposed alternative explanations, it’s likely people with COVID-19 experience gastrointestinal symptoms because the virus directly attacks the gut tissue through ACE2 receptors.