1 in 10 People May Still Have Infectious COVID-19 After 10 Days

The US Centers for Disease Control and Prevention (CDC) received a great deal of both positive and negative feedback after their decision to shorten the recommended isolation and quarantine period.

People with COVID-19 are now recommended to isolate for 5 days, and if they are asymptomatic or their symptoms resolve, the CDC says they should wear a mask around others for the next 5 days.

However, new research conducted by the University of Exeter suggests that 13% of COVID-19 patients are potentially infectious past the 10-day quarantine period.

The study, published in the International Journal of Infectious Diseases, collected samples from 176 people in Exeter who had PCR-tested positive for COVID-19. Investigators measured subgenomic RNA (sgRNA) and E gene genomic sequences in all samples.

They found that 13% of participants, about 1 in 10, were still exhibiting clinically relevant levels of virus after 10 days. While E-gene sgRNAs declined before E-gene genomic sequences, some participants retained infectious levels for up to 68 days. There were no clinical features previously correlated with prolonged viral clearance times.

Study supervisor Lorna Harries, PhD, a professor at the University of Exeter Medical School, said, “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”.

The study noted that PCR tests assess the presence of viral fragments. They can detect whether someone currently has or recently had COVID-19, but cannot determines whether the virus is still active and the person is still infectious.

The test used in this study gives a positive result only when the virus is active and capable of continuous transmission.

The investigators recommended their test be utilized among populations at high risk for severe COVID-19, to best stop the spread.