U.S. President Joe Biden tested positive again for COVID-19, "which was to be expected," his doctor said in a memo released by the White House, adding that the president feels well and will continue isolation measures.

After testing negative on Tuesday and Wednesday last week, Biden tested positive again for COVID on Saturday in what his doctor called a "rebound" seen in a small percentage of patients taking the antiviral drug Paxloid.

Paxlovid is an antiviral drug from Pfizer Inc. used to treat high-risk patients.