WASHINGTON (BLOOMBERG) - US President Donald Trump remains in a US military hospital outside Washington after contracting the coronavirus, as his physician said late Friday night (Oct 2) that the President was being treated with the antiviral drug Remdesivir and did not require supplemental oxygen.

As the day wore on, more and more prominent people in political circles revolving around Mr Trump tested positive for the virus. They include his campaign manager, Mr Bill Stepien, his former counsellor, Ms Kellyanne Conway and two Republican senators.

In a tweet, Mr Trump thanked Americans for their well wishes. "Going welI, I think! Thank you to all. LOVE!!!" he said.

He also spoke in a video he tweeted out: "We are going to make sure that things work out."

The White House said his symptoms were mild and that he would continue to work from a suite at the Walter Reed National Military Medical Centre in Maryland, but his hospitalisation heightened fears that his condition was more serious.

That Mr Trump, who is wary of doctors, agreed to go to Walter Reed is a sign of concern about his condition, several people familiar with the matter said.

Within the White House, several aides said they had received no more information about Mr Trump's condition than the public.

Earlier, White House physician Sean Conley issued a statement saying Mr Trump had been treated with a Regeneron Pharmaceuticals "antibody cocktail".

Regeneron shares spiked in late trading, rising more than 3 per cent after the market closed in New York.

The company's experimental treatment for Covid-19 hasn't been approved by the Food and Drug Administration, but Regeneron confirmed in a statement that it had provided a a single dose of the medicine for Mr Trump's use after receiving a "compassionate use" request from the President's doctors.

There will be no transfer of power from Mr Trump to Vice-President Mike Pence while the President is in the hospital, White House spokesman Judd Deere said.

The helicopter flight to Walter Reed was the most dramatic moment in a day of dizzying developments in Washington sparked by the President's disclosure of his illness just a month before Election Day.

As the Trump campaign was scrapping most of its planned events, the President's Democratic challenger, Mr Joe Biden, was campaigning in the battleground state of Michigan, where he delivered a speech while wearing a face mask.

Mr Biden, who took part in a chaotic debate with Mr Trump on Tuesday, expressed wishes for a speedy recovery for both Mr Trump and First Lady Melania Trump, who also tested positive for the coronavirus, and said the diagnosis was a "bracing reminder" to take the disease seriously.

Fresh anxiety over the virus continued to reverberate into Friday night. Mr Stepien, who was promoted to run the campaign this summer to help revive Trump's re-election bid, has been infected, a campaign spokesman said.

Mr Conway, who managed Trump's 2016 campaign before joining the administration, said she had tested positive.

"My symptoms are mild (light cough) and I'm feeling fine. I have begun a quarantine process in consultation with physicians," Ms Conway, who left the White House in August, wrote on Twitter.

The two Republican senators, Mr Mike Lee of Utah andMr Thom Tillis of North Carolina said that they, too, had tested positive.

Both sit on the Judiciary Committee, which is preparing for hearings on Mr Trump's nomination of Judge Amy Coney Barrett to the Supreme Court. The senators and Ms Conway attended the Rose Garden ceremony last Saturday in which Mr Trump announced Mrs Barrett's selection.

Senate judiciary chairman Lindsey Graham, who said he had tested negative, insisted that the confirmation hearings would begin as scheduled on Oct 12, but Democrats expressed alarm that Republicans still weren't taking enough precautions against Covid-19 on Capitol Hill.

On Friday evening, several top staffers gathered outside to see the President off, wearing masks.

Mr Trump and the marine who saluted him as he boarded Marine One also wore masks.

Face coverings had not been commonplace at the White House before 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," press secretary Kayleigh McEnany said in a statement.

Her statement wasn't issued until after financial markets closed in the US.

The drug that Mr Trump received at Walter Reed, Remdesivir, has been authorised to fight the virus in a number of countries.

It was cleared by the US Food and Drug Administration on May 1 for emergency use after research showed that the medicine, made by Gilead Sciences, helped hospitalised patients recover from Covid-19 more quickly than standard care alone.

Mr Trump and the First Lady had been in isolation at the White House since his diagnosis, which he announced after Bloomberg News reported that one of his closest aides, Ms Hope Hicks, had tested positive for coronavirus infection.

Mr Trump learnt of Ms Hicks's positive test on Thursday morning but continued with his planned schedule for the day, including a fund-raiser at his Bedminster, New Jersey, golf resort that raised US$5 million (S$6.8 million) for his campaign, according to people familiar with the matter.

Mr Trump and Ms Hicks had been in close contact in the days before her diagnosis. She travelled with him to the debate in Cleveland on Tuesday and to campaign events in Minnesota on Wednesday.