President Joe Biden tested positive for Covid late Saturday morning, by antigen testing, after testing negative several days in a row, his doctor said in a letter.
“After testing negative on Tuesday evening, Wednesday morning, Thursday morning and Friday morning, the President tested positive late Saturday morning, by antigen testing. This in fact represents ‘rebound’ positivity,” wrote White House physician Dr. Kevin O’Connor.
Biden, 79, has not experienced any re-emergence of symptoms and continues to feel well, O’Connor said. “This being the case, there is no reason to reinitiate treatment at this time, but we will obviously continue close observation.”
He will, however, return to strict isolation procedures, the doctor added.
“Folks, today I tested positive for COVID again. This happens with a small minority of folks,” the president tweeted Saturday.
“I’ve got no symptoms but I am going to isolate for the safety of everyone around me," Biden continued. "I’m still at work, and will be back on the road soon.”
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This story first appeared on NBCNews.com.