People who contract COVID-19 could still be infectious for more than two months, warns new research. Of course, remaining contagious for this long is far less likely, but scientists hope to expand the study to get a better idea of just how many people could be long carriers.

Researchers at the University of Exeter in England report that 13 percent of patients are still infectious and show clinically-relevant levels of the virus after 10 days of quarantine. In the most extreme of these cases, individuals were still carrying the virus for 68 days. There is nothing “clinically remarkable” about the people who remain with high levels of the virus, according to the study, which means it could happen to anyone.

For the study, researchers applied a new test on 176 people who had tested positive on standard PCRs to determine whether the virus was still active. The results suggest the new test should be applied in settings where people are vulnerable to stop 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,” says study co-author Lorna Harries, a professor at the University of Exeter Medical School, in a statement. “Furthermore, there was nothing clinically remarkable about these people, which means we wouldn’t be able to predict who they are”.

Harries and her team warn that people should still be cautious about those who were recently infected. That’s especially the case after the Centers for Disease Control and Prevention lowered recommended isolation time to five days for infected patients.

“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,” says lead author Dr. Merlin Davies. “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.”

It wasn’t mentioned in the media release as to whether the team is in the process of following up with a larger study.