Recovered COVID-19 patients may not be completely virus free. That is according to a new study in China that found some people continued to shed coronavirus through phlegm and poop even when samples from their noses and throats came back negative.
The findings, published in the Annals of Internal Medicine, may help create new guidelines in considering whether a patient can no longer infect other people. Laboratories currently rely on nose and throat swabs to diagnose patients.
“These findings raise concern about whether patients with negative pharyngeal swabs are truly virus-free, or sampling of additional body sites is needed,” researchers said in a report.
For the study, the team took poop and phlegm samples from 133 COVID-19 patients at Beijing Ditan Hospital in China. Throat and nose swabs of 22 participants appeared free of coronavirus during the study.
After a follow-up test, phlegm and poop samples from the same group appeared with the virus. The samples remained positive 13 to 39 days after the patients’ pharyngeal samples tested negative.
The researchers said if patients continue to release the coronavirus when they return home and resume regular daily activities, they might pose a risk to others. The study backs earlier research that found virus particles in infected people’s poop.
In one study, coronavirus appeared in stool samples taken from the toilet bowls and sinks of three patients in Singapore. The Chinese Center for Disease Control and Prevention made the same discovery that viable virus particles could stay in coronavirus patients’ poop.
However, an expert said that the presence of the virus in feces may not put many people at high risk of contracting COVID-19.
“It’s been long known that, for many viral diseases, for a period of time after you recover you can still excrete some virus, but usually pretty low levels of it,” William Schaffner, a professor of preventive medicine and infectious diseases at Vanderbilt Medical University, told Business Insider. “I don’t think it’s going to be a problem here, where we literally flush the fecal material with the virus down the drain.”
But he noted that the viral particles in phlegm could contribute to the spread of coronavirus, especially in hospitals.