….According to a CDC review of 113 studies, COVID-19 is only contagious ranging from two to three days before symptom onset to eight days after.

“That’s why the CDC recommends that people be exempted from any sort of PCR surveillance testing for 90 days after a positive test,” Gigi Gronvall, PhD, senior scholar at the Center for Health Security at the Johns Hopkins Bloomberg School of Public Health, told Verywell. Gronvall works with the center’s COVID-19 Testing Toolkit. “I expect that that this guidance is probably going to change at some point with more information, but some people continue to test positive by PCR even after they’re clearly no longer infectious. For whatever reason, there is still viral genetic material hanging out in their nose.”

Rapid tests are less sensitive, but a person will probably still test positive for six or seven days after they are no longer having symptoms, Gronvall said.