Joe Biden continued to test positive for coronavirus on Sunday and will “continue his strict isolation measures” his physician said.

The US president feels well, the White House said. Biden tweeted about the economy and about regretting being unable to meet in person to commiserate with military veterans and their families visiting Capitol Hill in support of a long-awaited bipartisan bill that would expand healthcare access for those exposed to toxic burn pits.

Some Republican senators had reversed their support for the legislation at the last minute.

Biden tweeted a video of himself sitting outside at the White House on a green sofa, wearing an open-necked blue shirt and a baseball cap with the presidential seal as he video-chatted with the families gathered on the steps leading up to the US Congress and had pizza sent to them.

The president on Saturday tested positive for Covid-19 only days after testing negative and having apparently largely shrugged off an infection with the virus.

His physician, Kevin O’Connor, said on Sunday that Biden is being monitored daily and his positive test that morning was unsurprising.

The president had originally contracted Covid and tested positive on July 21, then apparently recovered.

But Biden had been taking the anti-viral medication Paxlovid, which has reported numerous cases of effectively reducing the viral load of Covid only for it to return once the medication is stopped.

In accordance with Centers for Disease Control and Prevention guidelines, on Saturday Biden, 79, had re-entered isolation for at least five days. The agency says most “rebound” cases remain mild and that severe disease during that period has not been reported.

Paxlovid has been proven to significantly reduce severe disease and death among those most vulnerable to severe Covid.

Biden is fully vaccinated, after getting two doses of the Pfizer coronavirus vaccine shortly before taking office, a first booster shot in September and an additional dose 30 March.

The weekend positive tests jeopardize a Tuesday trip Biden had planned to Michigan, which is holding its fiercely-contested primary elections that day.