People with Covid can shed the virus in their faeces for seven months after infection and those who do often have gut problems, a new study found.
Despite being Covid-negative, patients often experienced nausea, abdominal pain, and vomiting - even after their other signs had long faded, said Stanford Medicine scientists.
Researchers say the study adds to mounting evidence that Covid actively infects the gut, and this infection continues for people who suffer from Long Covid, the Mirror reports.
Scientists are keen to understand why most people recover from the virus in a few weeks whilst others experience continued health problems months later.
The new study says the answer could be 'hidden reservoirs' of the virus throughout the body.
Study author Dr Ami Bhatt, also an associate professor of medicine and genetics for Stanford Medicine, researches how the microbiome - the vast universe of bacteria that carpets the lining of our intestines - affects human health.
She is eager to study whether an individual's bacterial "gutprint" affects whether, how and for how long the virus is shed in their faeces after an infection with Covid.
Dr Bhatt and her colleagues wanted to track what was happening in the majority of patients - those with mild illness.
The study involved 113 participants taking samples over the course of several months.
The discovery that a small number of participants, 3.8 percent, were still shedding coronavirus in their stool samples seven months after infection could indicate a source for this widespread phenomenon.
In the study, they found traces of Covid RNA in 85 percent of the samples of those currently infected with the virus.
After a week this fell to half and by four months only 12 percent still had a positive stool sample.
"No one really knows what causes long Covid," says study author Dr Ami Bhatt, who is an associate professor of medicine and genetics for Stanford Medicine at Stanford.
"Maybe long Covid — and the wide variety of symptoms it causes — is due to the immune system's response to viral proteins in hidden reservoirs throughout the body," she added.
For example, she speculates that people with long Covid who experience cognitive symptoms, known as 'brain fog', could have a lingering SARS-CoV-2 infection in their nervous system - in the same manner as those with lingering stomach problems were more likely to continue shedding the virus through their faeces.
There are some challenges to these results.
The study took samples and data from a larger piece of Stanford medical research, which asked participants to seal their samples in a bag that would deactivate the virus.
This means the scientists could only identify the dead fragments of the virus, so were unable to state categorically that the gut holds live coronavirus.
In answer to this, the authors of the study point to similar viruses to Covid being found in people's intestines during post-mortems, including a recent discovery of gastrointestinal covid in an autopsy.
What were the Long Covid gut symptoms identified in this study?
This study identified a wide range of different reported symptoms of Long Covid, that they believe could be linked to their study's findings. They are:
- Headache
- Runny nose
- Body ache
- Abdominal pain
- Nausea
- Vomiting
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