US President Joe Biden ended his Covid isolation Wednesday, telling cheering aides that his quick recovery from infection should inspire Americans to take advantage of free vaccines and treatments.

"I thought I heard a rumbling in my staff saying, 'He's back,'" Biden joked to a crowd of staff in the Rose Garden after he emerged from the White House residence for the first time since ending a five-day isolation period. "Thanks for sticking around."

Wearing his beloved Aviator sunglasses under a scorching sun, the 79-year-old Democrat noted the difference when Republican Donald Trump got Covid and had to be airlifted to hospital at the height of the pandemic in October 2020, before vaccines were available.

"When my predecessor got Covid, he had to get helicoptered to Walter Reed Medical Center. He was severely ill. Thankfully, he recovered. When I got Covid, I worked from upstairs of the White House, in the offices upstairs, for the five-day period," Biden said.

Biden said that being fully vaccinated, taking preventative tests, then using the Paxlovid therapeutic to speed up recovery from infection, prevents deaths and is all available at no cost.

"You don't need to be president to get these tools," he said, urging Americans to visit the covid.gov website for information. "The same treatment I got is available to you."

"Let's keep emerging from one of the darkest moments in our history," Biden said, before finishing his nine-minute address with an enthusiastic: "And now I get to go back to the Oval Office."

Biden had tested positive for coronavirus last Thursday and experienced a hoarse voice and fatigue. He worked from his residence with a somewhat lighter schedule than normal.

The official White House doctor said Wednesday he gave the all clear after two negative tests.

"Given these reassuring factors, the president will discontinue his strict isolation," presidential physician Kevin O'Connor wrote in a memorandum.

While now out of isolation, the president will wear a mask for 10 days when around others and continue to test regularly for the virus in case of a "rebound," O'Connor said.

Biden has no fever, the doctor added, noting "his symptoms have been steadily improving, and are almost completely resolved."

Biden is the oldest person ever in the US presidency, but his physician says he is generally in good health. He has been fully vaccinated and received two booster shots against the coronavirus.