US President Joe Biden's condition has improved since he first tested positive for Covid-19, the White House has said.

The 79-year-old is experiencing mild symptoms, including a runny nose and fatigue. His doctor says he is responding well to medication.

Mr Biden has continued working while in isolation, according to the White House, and on Thursday tweeted that he was "doing great".

The president is expected to resume normal duties once he tests negative.

An update released on Friday by the president's physician, Dr Kevin O'Connor, noted Mr Biden had a slight fever on Thursday evening that responded well to Tylenol.

The president still has an occasional cough, and his pulse, blood pressure and oxygen saturation levels remain "entirely normal", Dr O'Connor added.

In a Zoom meeting with his economic and energy advisers on Friday, Mr Biden sounded hoarse but said he was "feeling much better than I sound".

The president is still also being treated with Paxlovid, an anti-viral medicine that helps stop the Covid virus from multiplying in the body. This, in turn, allows the immune system to better combat the infection.

In a news briefing at the White House, press secretary Karine Jean-Pierre said she had spoken to the president and that "he wants to remind Americans to get vaccinated".

Ms Jean-Pierre added that the president had been "very active" and felt well enough to work an eight-hour day, which also included virtually receiving the president's daily briefing produced by US intelligence agencies.

Dr Ashish Jha, the White House's Covid response co-ordinator, said that Mr Biden had "slept well last night".

"He ate his breakfast and lunch, fully," he added. "He actually showed me his plate."

Dr O'Connor added that he believes the president - who is fully vaccinated and boosted - "will respond favourably [to the medication], as most maximally protected patients do."

"There has been nothing in the course of his illness so far which gives me cause to alter that initial expectation," Dr O'Connor said.

The presidential doctor's assessment was echoed by his chief medical adviser, National Institute of Allergy and Infectious Diseases director Dr Anthony Fauci, who told CBS that he "fully expects" Mr Biden to "do very well".

"[Mr Biden] is generally a healthy person. He has been vaccinated and boosted twice... and is feeling well enough to perform duties from the White House," Dr Fauci added.

White House officials have confirmed that Vice-President Kamala Harris, as well as the First Lady, Jill Biden, have so far tested negative for the virus. Both were being considered a close contact of the president.

The president is continuing to isolate in the White House, while his wife - following her original schedule - will travel home to Wilmington, Delaware, for the weekend.

On Friday reporters grilled White House officials as to why a maskless Ms Harris had hugged someone during an event earlier in the day in Washington DC.