White House physician Dr. Kevin O'Connor said in a letter that Biden "has experienced no reemergence of symptoms, and continues to feel quite well." O'Connor said "there is no reason to reinitiate treatment at this time."

In accordance with Centers for Disease Control and Prevention guidelines, Biden will reenter isolation for at least five days. He will isolate at the White House until he tests negative. The agency says most rebound cases remain mild and that severe disease during that period has not been reported.

Word of Biden's positive test came — he had been negative Friday morning — just two hours after the White House announced a presidential visit to Michigan this coming Tuesday to highlight the passage of a bill to promote domestic high-tech manufacturing. Biden had also been scheduled to visit his home in Wilmington, Delaware, on Sunday morning, where first lady Jill Biden has been staying while the president was positive. Both trips have been canceled as Biden has returned to isolation.