Tests also differ in their sensitivity, and people differ in how they perform them. “Some people do a Pap smear and it’s like they barely touch their nose,” said Dr. Gordon. “Whereas with other individuals — actually, recently with a relative, I’ve had to be like ‘don’t hurt yourself,’ because they really, really got into it.”
What must we do
One lesson is that long-lasting positive results are often enough that people who leave isolation before day 10 should continue to take precautions, such as wearing a well-fitting mask, experts say.
Further, scientists disagreed. Some advised isolating people until they test antigen negative, even if it takes more than 10 days.
“We can now tailor recommendations to individual experiences using the rapid test results to guide us,” said Dr. Grad. “And since we know that some people can take long-term courses, it seems reasonable to me that if you’re able to continue isolating if you’re positive, you should too.”
But several others said there’s no point in asking most otherwise healthy people to isolate or even continue testing for more than 10 days because of public health policy.
“Nobody’s saying there aren’t humans, maybe statistically at the end of the tail, who could be transmitting after day 10,” said Dr. Chin-Hong. But people at that stage of infection probably won’t play a huge role in the spread of the virus, and if they continue testing, many people could stay away without much of a public health benefit, he said. “And you also bring up an equality issue,” he added, “like, ‘Who the hell can have enough tests?'”
Even then, experts say, there are some circumstances where people should continue testing and may need to isolate after day 10. This includes people whose symptoms do not improve and people with reduced immunity, because they can shed the infectious virus for a longer period of time. (The CDC recommends that people with weakened immune systems isolate for: up to 20 days†
SOURCE – www.nytimes.com