Virus that causes COVID-19 can linger in digestive tract

COVID-19 patients can harbour the SARS-CoV-2 virus in their faeces for months after infection, say researchers.

In the largest study so far tracking the novel coronavirus’s RNA in faeces, researchers at Stanford University, California, found that around half of COVID-19 patients shed faecal RNA in the week after diagnosis, and 4% were still shedding faecal viral RNA seven months after diagnosis.

Many patients who have recovered from COVID-19 have reported a range of persistent symptoms as part of Long COVID.

Natarajan et al found that patients who had faecal SARS-CoV-2 RNA were also likely to have gastrointestinal symptoms such as abdominal pain, nausea and vomiting.

Coronavirus in the gut

Early on in the pandemic, researchers in China had found that the digestive tract was the main site apart from the respiratory system where SARS-CoV-2 could linger. When traces of the virus were found in faecal matter soon after the virus had emerged, many countries implemented wastewater surveillance to track the pandemic’s spread. 

The data gathered so far has found that SARS-CoV-2 RNA continues to be found in faeces long after respiratory shedding of the virus has stopped.

Natarajan et al say their data shows “SARS-CoV-2 infects the GI tract and that this infection can be prolonged in a subset of individuals with COVID-19” who go on to have persistent gastrointestinal symptoms.

Viral persistence

In addition to persistent gastrointestinal infection, SARS-CoV-2 may also linger in parts of the body that are protected from our immune system. Organs like the eyes, testes or brain are often no-go areas for our immune cells because the damage that could be caused by a reaction in the tissues is outweighed by the risk of infection.

The Ebola virus, for example, has been found to persist in the eyes, spinal fluid and semen of survivors long after their initial symptoms eased off – up to 18 months in some cases. Zika virus can also linger in the testes for many months. 

Earlier this year, research suggested that SARS-CoV-2 could also be harboured in the testes.

Persistent COVID-19 infection

Many patients who have recovered from COVID-19 have reported a range of persistent symptoms as part of Long COVID. The finding of SARS-CoV-2 viral shedding in 4% of COVID-19 patients seven months after infection suggests that a small minority of patients may have gastrointestinal symptoms related to infections months after an acute illness.

The implications of such gastrointestinal infections for other Long COVID symptoms, such as fatigue, nausea, and depression, are less clear, particularly since human gastrointestinal tracts are full of a huge range of germs, many of which cause no problems as long as they stay within the gastrointestinal tract. Hopefully further research will shed light on any connections between longer term SARS-CoV-2 gastrointestinal infections and broader Long COVID.

The data emerging on the gastrointestinal tract could not only offer more insight that could help us understand Long COVID but also improve wastewater surveillance. The virus being shed in faecal matter may not actually indicate current high levels of SARS-CoV-2 transmission.