The Perfect Enemy | How long is someone with COVID contagious?
August 17, 2022
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BOSTON – How long is someone with COVID-19 contagious and when can they safely come out of isolation? Researchers in Boston hope a study will shed some light on those questions.

Experts believe you’re most contagious two days before your symptoms begin and during the first three days of illness. But researchers at Brigham and Women’s Hospital wanted to see if rapid antigen testing can help determine when it’s safe to return to public life.  

So they took 40 individuals with COVID-19 and had them perform rapid antigen tests six days after the onset of symptoms or after their initial positive test, whichever came first. Swabs were also sent for viral culture, considered a more accurate measure of contagion.  

They found that 75% of the participants still had positive rapid antigen tests on day six. However, only half of them had positive viral cultures.  

Also, all of the people who tested negative by rapid antigen on day six had negative viral cultures. The researchers say these findings suggest that even if someone has lingering symptoms if they have a negative rapid antigen test on day six, they may be able to safely end isolation.  

And if someone is still testing positive on day six but has no symptoms, they may also be able to safely end isolation.  

That said, the CDC still recommends that when people do come out of isolation after five days, they should continue to wear a mask for another five days to protect others.