Coronavirus Lingered in the Stool Samples of COVID-19 Patients for 22 Days, Study Shows

The coronavirus appears able to linger in COVID-19 patients' stools longer than their respiratory system, according to a study.

The research, published in the journal the BMJ, involved 96 COVID-19 patients being treated at a dedicated COVID-19 hospital in the eastern province of Zhejiang, China. Twenty-two of the participants had a mild form of the disease, defined as having no or mild pneumonia. The remaining 74 patients had severe COVID-19, with symptoms including breathing problems. Of those, 30 were treated in an intensive care unit. The data on the patients, aged 55 years old on average, was collected between January 19 and March 20. All patients tested negative of the coronavirus by March 20, and none died.

The researchers looked for the genetic material of the coronavirus in almost 3,500 respiratory, stool, blood serum and urine samples taken daily from the patients. They also assessed the participants' medical records to see if they could find a link between viral loads—the levels of the germ present in samples—and how sick they were.

The team found the RNA, or the genetic material, of the virus in the stool samples of 55 patients, and the blood serum of 39. One urine sample tested positive for the coronavirus.

On average, the virus lingered in stool samples for 22 days. This was "significantly longer" than the 18 days in respiratory samples, and 16 days for serum.

By looking at data on severe patients specifically, they saw the virus was detectable for 21 days on average, "significantly longer" than in mild patients at 14 days.

In mild patients, their viral loads peaked in respiratory samples in the second week after their symptoms came on. However, in the seriously ill patients, levels were still high in the third week. The virus stuck around longer in patients aged 60 and over, and males, the team said.

Using the name of the coronavirus which causes COVID-19, the authors wrote: "The duration of SARS-CoV-2 is significantly longer in stool samples than in respiratory and serum samples, highlighting the need to strengthen the management of stool samples in the prevention and control of the epidemic, and the virus persists longer with higher load and peaks later in the respiratory tissue of patients with severe disease."

They added: "Consistent with earlier reports of SARS-CoV-2, we found differences in the viral load in patients with different disease severities, those with severe disease showing a significantly higher viral load than those with mild disease, which suggests that viral load can be used to assess prognosis."

The study suggests the role of feces in the spread of the coronavirus "cannot be ignored," the scientists said, but more research is needed to uncover how important the viral load in stools is in preventing and controlling the spread of the bug.

The study had several limitations, the researchers said, including that it involved patients only from one hospital, and the sample size was too small to compare the effects of treatments in subgroups. Also, many factors affect the viral load in a sample, including how well it was collected, they noted. In addition, the testing method they used didn't distinguish between viable and non-viable virus, or tell them anything about its ability to replicate.

Ian Jones, professor of virology at the University of Reading in England, who did not work on the research, told Newsweek, "The study shows that the sicker a patient is, the more virus is present and that it lasts for longer. This is more or less what would be expected although it is good to see the times defined.

"Virus was also found in body secretions other than respiratory samples but at a lesser level. This has been seen before and although it is worth noting it should not detract from the main route of infection, which is via respiratory droplets. Stopping these will have by far the most impact in reducing transmission."

According to Johns Hopkins University, more than 2.7 million COVID-19 cases have been diagnosed worldwide, and 190,890 have died. Over 743,000 people are known to have survived. The Statista graph below shows the U.S. is the country with the most reported cases.

Earlier this month, a separate team found that diarrhea may be the first or only symptom some COVID-19 patients experience.

Brennan Spiegel, professor of medicine and public health at Cedars-Sinai and co-author of the study published in The American Journal of Gastroenterology, told Newsweek: "I think the main message is COVID-19 is not just cough."

This is article has been updated with comment from Professor Ian Jones.