1 in 10 People With COVID Still Infectious After 10 Days: Study

Friday, January 14, 2022 – One in 10 people infected with COVID-19 can remain infectious after 10 days, and some may remain contagious for up to two months, a new study suggests.

British researchers report that a new test can detect whether the coronavirus is still active. They used it to analyze samples from 176 people who tested positive on standard PCR tests.

After 10 days, 13% of the people had levels of active virus, indicating that they may still be contagious. These levels persisted in some participants for up to 68 days, according to the study.

Lorna Harris, a professor at the University of Exeter Medical School who led the study, said: “While this is a relatively small study, our results suggest that a potentially active virus can sometimes persist for longer than 10 days, and could pose a potential transmission risk.” . studying.

“Moreover, there was nothing clinically observable about these people, which means we won’t be able to predict who they are,” Harris added in a university news release.

Standard polymerase chain reaction (PCR) tests check for viral fragments and can reveal whether someone has recently had coronavirus, but not whether they are still active. The new test – which is not yet available – gives a positive result only when the virus is active and potentially contagious.

The results were published online on December 7 at International Journal of Infectious Diseases.

The researchers suggested that although more research is still needed, the new test may be useful in certain settings to protect those at risk.

In some settings, such as residential care facilities, people who return after illness and continue to become infected after 10 days can pose a serious public health risk, according to lead study author Merlin Davies, of the University of Exeter Medical School.

“We may need to make sure that people in those places have an active virus test negative to make sure that people are no longer contagious,” Davies added. “Now we want to do larger trials to investigate this further.”

In the United States, current quarantine guidelines allow people who have tested positive for COVID-19 to leave isolation after five days if they are asymptomatic or if their symptoms resolve (without a fever for 24 hours). The US Centers for Disease Control and Prevention says they should wear masks for the next five days.


  • University of Exeter, press release, 13 January 2022

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