Can coronavirus spread through poo?
A new study suggests that certain protein-digesting enzymes help the new coronavirus enter cells in the gut.
Researchers in a new study have said that the novel coronavirus may not spread via contact with faecal matter. However, they have not definitively ruled out faecal-oral transmission of COVID-19.
According to a report published in Science Immunology on Wednesday, in laboratory experiments, the researchers discovered that while the virus does infect the cells of the small intestine, fluid from the large intestine inactivates it, so that the virus is no longer infectious by the time it is excreted in feces.
The authors caution, however, that because they only studied faecal samples from 10 patients, they cannot definitively rule out faecal-oral transmission of COVID-19. Their findings also suggest that certain protein-digesting enzymes help the new coronavirus enter cells in the gut.
Blocking those two enzymes might be a way to treat the infection, they speculate, especially since a drug that inhibits the TMPRSS2 enzyme is already approved in Japan to treat pancreatitis.
According to the World Health Organisation (WHO), there is some evidence that COVID-19 infection may lead to intestinal infection and be present in faeces. However, to date only one study has cultured the novel coronavirus from a single stool specimen.
There have been no reports of faecal−oral transmission of the COVID-19 virus to date, says the agency.
The novel coronavirus or SARS-CoV-2 gains entry into human cells by latching onto protein receptors called ACE2, which are found on certain cells’ surfaces.
Around 2% of the cells lining the respiratory tract have ACE2 receptors, while they’re also found in the cells lining the blood vessels. But the greatest numbers of ACE2 receptors are actually found in the cells lining the gut. Around 30% of cells lining the last part of the small intestine (called the ileum) contain ACE2 receptors.
Researchers 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 is likely that people with COVID-19 experience gastrointestinal symptoms because the virus directly attacks the gut tissue through ACE2 receptors.
A recent study from China found just over half of 73 hospitalised patients with COVID-19 had virus in their faeces. Many of them did not have gastrointestinal symptoms.
While testing stool samples may not be an efficient way to diagnose the new coronavirus in individuals – it is normally slower than testing samples from the respiratory tract – researchers are looking at faeces to detect population outbreaks of the deadly disease.
More than a dozen research groups worldwide are collaborating on a project analysing wastewater for the presence of coronavirus in target populations. But just because the virus is found in faeces, it doesn’t mean it’s necessarily infectious when shed from the stool. There is more research needed to prove whether this is the case.
COVID-19 SEEMS TO LAST LONGER IN FAECES
One study in China followed 74 COVID-19 patients in hospital by taking throat swabs and faecal samples daily or every second day. The researchers found in over half of patients, their faecal samples remained positive for coronavirus for an average of just over 11 days after their throat swabs tested negative.
Coronavirus was still detected in one patient’s faeces 33 days after their throat swab had turned negative. This suggests the virus is still actively reproducing in the patient’s gastrointestinal tract long even after being cleared from the respiratory tract.
Various studies are being conducted across the world to gather more information on how well the coronavirus survives in the gut, how it causes gastrointestinal symptoms like diarrhoea and how the virus survives in faeces at different temperatures.
In one study, researchers collected samples from the bathroom of a COVID-19 positive patient with no diarrhoea.
Samples from the surface of the toilet bowl, sink and door handle returned positive for the presence of the virus. Hence, handwashing, particularly after using the toilet, is an absolute must.
The novel coronavirus can survive for up to three days on plastic and stainless-steel surfaces. So we need to regularly disinfect surfaces that will be touched when using toilets including doorknobs, door handles, taps, support rails and toilet control handles.