COVID-19 infection lingers in the gut, even after it clears the respiratory system, researchers say

September 8, 2020, 3:27 AM UTC

COVID-19 patients have active and prolonged gut viral infection, even in the absence of gastrointestinal symptoms, scientists in Hong Kong showed.

The coronavirus may continue to infect and replicate in the digestive tract after clearing in the airways, researchers at the Chinese University of Hong Kong said in a statement Monday. The findings, published in the medical journal GUT, have implications for identifying and treating cases, they said.

SARS-CoV-2 spreads mainly through respiratory droplets — spatters of virus-laden discharge from the mouth and nose, according to the World Health Organization. Since the first weeks of the pandemic, however, scientists in China have said infectious virus in the stool of patients may also play a role in transmission.

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A February study of 73 patients hospitalized with the coronavirus in China’s Guangdong province found more than half tested positive for the virus in their stool.

The Hong Kong scientists studied stool samples from 15 patients to better understand the virus’s activity in the gastrointestinal tract. They found active gut infection in seven patients, some of whom had no nausea, diarrhea or other digestive symptoms. Three patients continued to display active viral infection as long as six days after their respiratory samples tested negative for COVID-19.

The finding “highlights the importance of long-term coronavirus and health surveillance and the threat of potential fecal-oral viral transmissions,” Siew Chien Ng, associate director of the university’s Centre for Gut Microbiota Research, said in the statement.

Treatments that modulate the composition and functionality of the gut microbiome should be explored, according to Ng. The gut bacteria of patients who were particularly infectious showed a loss of protective microbes and a proliferation of disease-causing ones.

The Chinese University has offered free screening stool tests to travelers arriving at the airport since late March, and identified six infected children among more than 2,000 samples tested. From Monday, up to 2,000 Covid-19 tests will be done daily as part of targeted detection of asymptomatic people.

More than one patient tested positive even though their respiratory samples were negative, said Francis K.L. Chan, the university’s dean of medicine and director of the Centre for Gut Microbiota Research.

“Stool test is accurate and safe, making it suitable and more effective for COVID-19 screening for specific groups of people,” Chan said in the statement. Some regulators including the U.S. Food and Drug Administration have reached out about stool tests.