Viral RNA from SARS-CoV-2 can be detected in patients weeks after symptom onset and often after respiratory swabs have become negative, two studies show.

Whether or not the virus is viable in such stool samples is unknown, but the findings bring concern that some patients with COVID-19 could be a source of infection in the weeks after they have “recovered”.

In the first study — a meta-analysis of 12 studies reporting stool analyses published in Gastroenterology by Hong Kong researchers — 48% of stool samples taken from 138 patients tested positive at some point during their COVID-19 illness.

In nine of the included studies, 127 patients had repeated stool tests, and 70% of these patients continued to test positive for the virus in stool samples after their respiratory swabs had become negative.