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COVID-19: a 10-day quarantine is not enough for everyone, according to a study

A new study suggests 10 days of quarantine may not be enough, finding one in 10 people may still remain infectious even after that point.

According to a small study from the UK, which was published in the International Journal of Infectious Diseases in December and looked at 176 patients who had previously tested positive for COVID-19 with PCR, a new type of test found that some patients were infectious for longer than the standard 10-day quarantine period.

“Although a relatively small study, our results suggest that potentially active virus can sometimes persist beyond a 10-day period and could pose a potential risk for onward transmission,” said Lorna Harries, Professor at the University of Exeter Medical School. supervised the study, said in a press release. “Furthermore, there was nothing clinically noteworthy about these people, which means we wouldn’t be able to predict who they are.”

PCR tests are the gold standard for identifying if someone has COVID-19 and work by looking for viral fragments. But they don’t tell us whether a person is currently infectious or not, according to the study, because these fragments may still be present in the system after viral clearance.

Another way to test is to look for subgenomic RNAs, the researchers said, which are produced when a virus is actively replicating.

Researchers examined RNA from samples collected from 176 people who had previously tested positive by PCR for COVID-19 between March 17, 2020 and November 29, 2020. Of these patients, 74 were asymptomatic, 36 had disease mild, 22 had moderate disease. disease and 33 were classified as having severe disease.

They found that 13% of sgRNA-positive cases still had clinically relevant virus levels after 10 days.

For 17 people in the study, subsequent samples were available. Five of these individuals showed sgRNA-positive up to 68 days.

The researchers believe this type of testing could be implemented in high-risk scenarios, such as testing healthcare workers or those working in long-term care.

“In some settings, such as people returning to nursing homes after illness, people who continue to be infectious after ten days could pose a serious public health risk,” said Merlin Davies, lead author of the study, in the press release. “We may need to make sure people in these settings have an active negative virus test to ensure that people are no longer contagious. We now want to conduct larger trials to explore this issue further. »

Some previous studies have suggested that the presence of sgRNA does not mean that the virus is definitely active, and the researchers acknowledged that the issue requires further investigation.

But it does suggest that the 10-day rule may not be absolute for all cases.

“Given the clear potential for onward transmission that these cases may possess, more targeted studies to detect and investigate secondary cases with transmission beyond 10 days should now be undertaken in these populations,” the study states in its conclusion. .