Many people who become infected with Sars-CoV-2 complain of vomiting and diarrhea in addition to typical cold symptoms. Oncologist and geneticist Ami Bhatt noticed this in the first, chaotic days of the pandemic. “At the time, people thought it was just a respiratory virus,” she says. Bhatt and her colleagues at Stanford University in California decided to investigate the cause of the gastrointestinal symptoms and began collecting stool samples from people with Covid-19.
At that time, the researchers were not the only ones who were surprised. The gastrointestinal symptoms of many patients also surprised the internist Timon Adolph, who works thousands of kilometers from Bhatt’s laboratory at the Medical University of Innsbruck in Austria. Together with his team, he therefore also collected samples – biopsies of gastrointestinal tissue.
Two years later, the researchers’ foresight paid off: Both groups recently published study results that indicate that parts of Sars-CoV-2 sometimes remain in the intestine for months after an initial infection. The data ties well with a body of work suggesting that stubborn virus remnants – “coronavirus ghosts,” as Bhatt calls them – may be contributing to the origins of Long Covid. However, the teams have not yet been able to prove a direct connection between the persistent virus fragments and Long Covid. Further studies are therefore necessary, explains Bhatt: “And they are not easy.”
Mysterious long-term complaints
Doctors usually use the term Long Covid to describe symptoms that last longer than twelve weeks after an acute infection. More than 200 symptoms of varying severity have already been linked to Long Covid. Researchers are still puzzling over the cause. Various theories link the phenomenon to harmful immune responses, tiny blood clots, and residual virus reservoirs in the body. Many researchers assume that a mixture of these factors is responsible for the long-term effects.