Masked Trump waves to well-wishers as he walks to helicopter to be airlifted to Walter Reed

Donald Trump has been airlifted to hospital less than a day after testing positive for coronavirus, upending his re-election campaign.

Wearing a black face mask, the president waved as he crossed the White House lawn to board the Marine One helicopter for a brief ride to the Walter Reed Military Medical Centre in Bethesda, Maryland, at about 5.30pm on Friday.

The president will spend “a few days” at the hospital as a “precautionary measure” after he and Melania Trump, as well as as number of top Republican figures, reported positive Covid-19 tests within the last 24 hours.

“President Trump remains in good spirts, has mild symptoms, and has been working throughout the day,” press secretary Kayleigh McEnany said on Friday. “Out of an abundance of caution, and at the recommendation of his physician and medical experts, the president will be working from the presidential offices at Walter Reed for the next few days.”

Mr Trump has been treated with an experimental antibody cocktail for Covid-19 and his physician, Dr Sean Conley, said in a statement that his patient “remains fatigued but in good spirits”. The 74-year-old president is reportedly suffering a fever and cough. According to his physician's memo, he is also taking vitamin D, zinc, melatonin, a daily aspirin and an antacid.

However, he remains in power and has not transferred control of the executive to Mike Pence, the vice president, the White House said.

The president announced on Twitter late on Thursday that he and his wife had tested positive for Covid-19. The couple were tested after senior aide Hope Hicks was found to be infected following an event at Mr Trump’s New Jersey golf club. Ms Hicks had also travelled to Minnesota for a fundraiser and a rally on Wednesday.

During a virtual address to the Alfred E Smith Memorial Foundation Dinner on Thursday night, an annual fundraiser for Catholic charities, the president once again made optimistic and misleading statements about the state of the public health crisis.

He said that a vaccine, of which there are several in late-stage clinical trials, was “on track” to be developed and distributed “before the end of the year, and maybe substantially before”. “I just want to say that the end of the pandemic is in sight, and next year will be one of the greatest years in the history of our country,” he said.

Several other prominent figures announced their positive diagnoses on Friday including Republican senators Mike Lee and Thom Tillis, and GOP chair Ronna McDaniel.

Before boarding Marine One on Friday evening Mr Trump recorded a video message, thanking supporters for their well wishes and saying he believed he was doing “very well”.

“We're going to make sure that things work out,” he added in his first tweet for a full day. “The first lady is doing very well. So, thank you very much, I appreciate it, I will never forget it. Thank you.” 

Mr Trump’s diagnosis has upended his re-election campaign. His team has postponed all upcoming events, including two rallies scheduled for this weekend, and scrambled to test its network across several potential points of transmission – all while sparring with the Commission on Presidential Debates over proposed rules for additional “structure” to upcoming events following the chaotic opener on Tuesday, 

It remains unclear when the president and first lady were exposed to the virus.

During a White House briefing on Thursday, Ms McEnany was asked whether it was appropriate that the president continued to hold rallies with thousands of supporters despite risks of infections in so-called "red zones" where infection rates remain high.

She said: “There really seems to be two standards of health in this country, one for Trump supporters and one for everyone else,” she said. “So it's vital if you're protesting, but somehow political speech is no longer vital when it comes to a Trump supporter.”

She told reporters on Friday that she did not discover Hope Hicks had caught Covid-19 until after she had held that press conference.

At least three White House news reporters received positive diagnoses on Friday.

Republicans have meanwhile pressed on with plans to confirm Amy Coney Barrett, the president's pick to replace the late Ruth Bader Ginsburg on the US Supreme Court, in the face of opposition from Democrats. The latter group say that lawmakers do not know the “full extent of potential exposure stemming from the president's infection".

Judge Barrett had been in close contact with the president over the weekend at a White House event announcing her nomination. She reported testing negative on Friday. Senator Lee was among three people at that event, including Mr Trump and Notre Dame president John Jenkins, who have since both tested positive for Covid-19.

Republican National Committee chair Ronna McDaniel, who last met with the president on 25 September, also announced she had tested positive.

Vice president Mike Pence, who could assume presidential duties if Mr Trump became too ill to perform them, tested negative on Friday. He has returned to Washington DC.

But the president has not transferred authority to Mr Pence, according to White House officials. “The president is in charge,” said White House communications director Alyssa Farah. 

The vice president's physician said he is “not considered a close contact with any individuals who have tested positive” and “does not need to quarantine” despite health guidelines that urge anyone to self-isolate for 14 days following the initial point of contact with an infected person.

The statement suggested that Mr Pence has not been in close contact with any administration official or staff who have also been in close contact with the president, first lady or Ms Hicks, though Mr Pence attended a coronavirus briefing at the White House Rose Garden on Monday and reportedly met with the president on Tuesday, two days before Mr Trump revealed the positive diagnosis, and placing him within the threshold for quarantine.

Mr Pence is scheduled to travel to Salt Lake City, Utah on Monday ahead of his debate on Wednesday against his Democratic opponent Kamala Harris.

In remarks on Friday, Democratic presidential candidate Joe Biden said Mr Trump’s diagnosis served as a "bracing reminder" for the need to take seriously an illness that has killed more than 200,000 Americans and infected millions of others.

While Mr Biden, who has tested negative for coronavirus, paused “negative” advertising in the wake of his election opponent’s ill health, he is hitting the campaign trail in Michigan this weekend. The former vice president said he and his wife, Dr Jill Biden, wished the Trumps well and were praying for them.