Joe Biden, the oldest person ever to serve as president of the United States, has tested positive for COVID-19, is experiencing mild symptoms and will continue working but in isolation, the White House said Thursday.

Biden, 79, has a runny nose, fatigue and an occasional dry cough, symptoms which he began to experience late Wednesday, White House physician Kevin O'Connor said in a note released Thursday. Biden has begun taking the anti-viral treatment Paxlovid, O'Connor said.

Fully vaccinated and twice boosted, Biden said he was "doing well" in a video posted on his Twitter account. In the 21-second clip, he also said he was "getting a lot of work done" and would continue with his duties.