1 in 10 COVID patients could be infectious after 10 days

potentially infection
© Oksana Krasiuk

New research indicates that after 10 days, one in ten people may still have clinically relevant levels of potentially infectious COVID

With COVID infection, scientists for two years have been certain that ten days – from the point of infection – is slightly more than enough to ensure the patient is no longer infectious. Under that understanding, majority-vaccinated countries across the world have shaved those ten days down to seven or five, aiming for the shortest isolation period possible.

Now, new research raises an alarming possibility – that some people could remain infectious, long after ten days.

Led by the University of Exeter and funded by Animal Free Research UK, samples from 176 people in Exeter who had tested positive on standard PCR tests were applied to a newly adapted test – to detect whether the virus was still active.

13% of people still exhibited clinically relevant levels after 10 days

Results, published in the international Journal of Infectious Diseases, found that 13% of those test still had potentially infectious levels of SARS-CoV-2, and some even retained these levels for up to 68 days.

Authors of the study believe this new test should be utilised in settings involving vulnerable people to help curb the spread of COVID-19.

“While this is a relatively small study, our results suggest that potentially active virus may sometimes persist beyond a 10 day period, and could pose a potential risk of onward transmission. Furthermore, there was nothing clinically remarkable about these people, which means we wouldn’t be able to predict who they are,” said Professor Lorna Harries, University of Exeter Medical School, who oversaw the study.

Researchers suggest “negative active virus” test

Currently, conventional PCR tests work through testing for the presence of viral fragments in subjects and can detect if someone has recently had the virus they are unable to detect whether it is still active and infectious.

Exeter’s new test only gives a positive result when the virus is active and potentially capable of onward transmission, making it an entirely new and potentially pandemic changing design.

Lead author Merlin Davies explored the importance of the new study. They said: “In some settings, such as people returning to care homes after illness, people continuing to be infectious after ten days could pose a serious public health risk.

“We may need to ensure people in those setting have a negative active virus test to ensure people are no longer infectious. We now want to conduct larger trials to investigate this further.”

The Animal Free Research UK CEO Carla Owen, said: “Once more, it shows how focusing exclusively on human biology during medical research can produce results that are more reliable and more likely to benefit humans and animals. […] The results also send a loud and clear message to the Government to better fund modern medical research and make the UK a world leader in cutting edge, kinder science.”

Find the full study here


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