SARS-CoV-2 persists in stool after respiratory samples test negative

Last Updated: 2020-03-24

By Will Boggs MD

NEW YORK (Reuters Health) - SARS-CoV-2 viral RNA can persist in stool samples long after respiratory samples have tested negative for the virus that causes COVID-19, researchers report.

Dr. Xi Huang from Fifth Affiliated Hospital, Sun Yat-sen University, Zhuhai, Guangdong Province, China and colleagues collected respiratory and fecal samples from 74 patients with COVID-19 diagnosed by two sequential respiratory tract samples that tested positive for SARS-CoV-2 by RT-PCR.

Fecal samples from 33 patients (45%) were negative for SARS-CoV-2 RNA, while their respiratory swabs remained positive for a mean 15.4 days from first symptom onset.

Among the 41 patients (55%) with positive fecal and respiratory samples, respiratory samples remained positive for SARS-CoV-2 RNA for a mean 16.7 days and fecal samples remained positive for a mean 27.9 days after first symptom onset, according to the online report in The Lancet Gastroenterology and Hepatology.

One patient had positive fecal samples for 33 days continuously after the respiratory samples became negative, and another patient tested positive for SARS-CoV-2 RNA in their fecal samples for 47 days after first symptom onset.

Fecal sample viral positivity was not associated with the presence of gastrointestinal symptoms or with COVID-19 disease severity, but antiviral treatment was positively associated with the presence of viral RNA in fecal samples.

"Although knowledge about the viability of SARS-CoV-2 is limited, the virus could remain viable in the environment for days, which could lead to fecal-oral transmission, as seen with severe acute respiratory virus CoV and Middle East respiratory syndrome CoV," the researchers note. "Therefore, routine stool sample testing with real-time RT-PCR is highly recommended after the clearance of viral RNA in a patient's respiratory samples. Strict precautions to prevent transmission should be taken for patients who are in hospital or self-quarantined if their fecal samples test positive."

"Determining whether a virus is viable using nucleic acid detection is difficult; further research using fresh stool samples at later timepoints in patients with extended duration of fecal sample positivity is required to define transmission potential," they add.

Dr. Danson Xue Wei Yeo from Tan Tock Seng Hospital, Singapore, who recently reviewed the possibility of fecal-oral transmission of SARS-CoV-2, told Reuters Health by email, "It is not surprising that the fecal viral RNA shedding pattern of SARS-CoV-2 is similar to that of SARS-COV. The surprising thing is that most of these patients do not have GI symptoms even though they have viral RNA in the feces."

"Fecal-oral transmission is still a strong possibility for SARS-COV-2, and proper hand hygiene must be emphasized," he said. "We should not let down our guard in patients who are discharged after treatment for COVID-19 and declared virus free, as they may still be shedding the virus in the feces."

"Patients whose fecal samples test positive for viral RNA should be followed up with further testing and remain in quarantine until negative," Dr. Yeo said.

Dr. Huang did not respond to a request for comments.

SOURCE: https://bit.ly/39bdqRm The Lancet Gastroenterology and Hepatology, online March 19, 2020.