75% of COVID patients tested positive, 35% had positive cultures, on day 6Three quarters of a group of nonhospitalized men and women newly diagnosed as having COVID-19 continued to have positive rapid antigen test (RAT) results—and over one-third still had viable virus on culture—6 days later, according to a study led by Brigham and Women's researchers.If confirmed, the findings, published yesterday in JAMA Network Open, challenge current US Centers for Disease Control and Prevention (CDC) COVID-19 guidelines stating that infected people with healthy immune systems can end isolation after 5 days if they have no symptoms or have improving symptoms and no fever.The authors noted that culturable virus is currently the best proxy for infectiousness and that RATs correlate with culture positivity early in COVID-19, although little is known about whether they continue to do so after day 5.From Jan 5 to Feb 11, 2022, 40 COVID-19 patients were enrolled.
Average patient age was 34 years, and 90.0% had completed a primary COVID-19 vaccine series and one booster dose. The dominant variant in Boston at that time was Omicron BA.1.Patients completed daily symptom logs and RATs.
On day 6, the researchers obtained samples for viral culture from 17 patients (42.5%). Ten patients (25.0%) tested negative on RAT on day 6, and all patients tested negative by day 14.
Average time to first negative RAT in the seven asymptomatic patients was 8.1 days, versus 9.3 in the 33 symptomatic patients.