One in 10 people can still spread Covid-19 after 10 days
One in 10 people may have clinically relevant levels of SARS-CoV-2 potentially infectious after a 10-day quarantine period, so it still has the capacity to infect, according to new research.
The study, led by the University of Exeter in the UK and funded by Animal Free Research UK, and published in the Journal of Infectious Diseases on Friday, used a newly adapted test that can detect whether the virus was potentially active. It was applied to samples from 176 people in that British town who had tested positive in standard PCR tests.
The study found that a 13% of people still exhibited clinically relevant levels of virus after 10 days, meaning they could be infectious.
Some maintained these levels for up to 68 days.
The authors believe that this new test should be applied in settings where people are vulnerable, in order to stop the spread of COVID-19.
“While this is 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 further transmission. Also, there was nothing clinically noticeable about these people, which means we couldn’t predict who they are,” says Lorna Harries, from the University of Exeter Medical School, who supervised the study.
Conventional PCR tests work by testing for the presence of viral fragments. While they can determine if someone has recently had the virus, they cannot detect if it is still active and if the person is infectious. However, the test used in the latest study gives a positive result only when the virus is active and potentially capable of forward transmission.
“In some settings, such as people returning to care homes after illness, people who remain infectious after 10 days could pose a serious public health risk. We may need to make sure people in those settings have an active negative virus test to ensure people are no longer infectious. We now want to carry out larger trials to investigate this further,” says Merlin Davies, from the University of Exeter Medical School.
CEO of Animal Free Research UK, Carla Owen, said: “The University of Exeter team’s discovery is exciting and potentially very important. Once again, 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 pioneering work without animals is providing the best opportunity not only to defeat to Covid-19, but also to find better treatments for all human diseases”, he concludes.