People who persistently test positive for COVID-19 after clinically recovering and adequately self-isolating are not likely to spread the virus to others, according to a new study that examined the NBA’s 2020 “bubble” in Orlando. 

After its season was interrupted by the pandemic last March, the NBA resumed its season in Orlando, Florida, as players were sequestered at Disney World to prevent against infections. Nearly 4,000 players, coaches, staff and vendors were tested daily for the coronavirus.

Researchers analyzed the testing data and published their findings Thursday in the Journal of the American Medical Association. 

Among the more than 3,600 people who participated in the study, 36 persistently tested positive for COVID-19 after being infected and otherwise seemingly recovering. They had contracted the virus before the basketball season resumed. Doctors allowed those individuals to return to team activities if had they completed their CDC-recommended isolation, were not experiencing symptoms and tests show elevated “reverse transcription polymerase chain reaction” values that indicated they were no longer infectious.

There were no instances of virus transmission during that stretch of the NBA season, from June 11 to Oct. 19, the study found. 

The researchers noted the professional basketball league made for a intriguing case study because it was one of the few examples of unmasked, close exposures between people who had recovered from COVID-19 but were still testing positive and uninfected individuals.

Christina Mack, one of the study’s authors, told HealthDay that persistently testing positive happens when someone sheds virus particles at a low level and that she’s seen cases in which a person still tests positive for COVID-19 four months after being infected.

The study said its findings support the CDC’s self-isolation guidelines. The public health agency suggests that anyone who knows or suspects they had symptomatic COVID-19 should not be around others until 10 days after symptoms first appear, they have gone at least 24 hours without a fever and other symptoms are improving. 

The researchers, however, noted that one limitation of their study was that it focused mainly on younger, healthy men.