U.S. President Donald Trump is being treated with the antiviral drug remdesivir and is “resting comfortably” after testing positive for the coronavirus and being admitted to hospital, his doctor has said.

The doctor, Sean P Conley said this late on Friday in a statement released by the White House after Trump was admitted to the Walter Reed medical centre.

“This evening I am happy to report that the president is doing very well,” Conley said.

“He is not requiring any supplemental oxygen, but in consultation with specialists we have elected to initiate remdesivir therapy.

“He has completed his first dose and is resting comfortably,” the White House physician continued.

The effectiveness of remdesivir, a drug originally developed by pharmaceutical giant Gilead to treat Ebola, is uncertain, with some research suggesting it can reduce recovery time and other research saying it has no benefits at all for COVID-19 patients.

Its makers say it can significantly reduce the chances of death in severe cases of COVID-19.

In a tweet, Trump himself said: “Going welI, I think! Thank you to all. LOVE!!!”

The president was flown to the Walter Reed hospital, a military facility that has historically treated presidents, by helicopter earlier on Friday out of what the White House said was an “abundance of caution.”

He walked out of the White House on his own and without assistance, giving a thumbs up as he boarded the Marine One helicopter.

In an 18-second video released before he set off, he was shown standing and wearing a blue suit and tie.

The 74-year-old president, who is in the high-risk category because of his age and weight, has exhibited what his staff called “mild symptoms.”

He has also been given an experimental antibody cocktail produced by drug-maker Regeneron.

His wife, Melania, also tested positive and has a cough and headache.

Trump’s illness, which was first announced to the world through his Twitter account in the early hours of Friday, has upended the presidential race, with just 32 days to go until the election.

Trump is in “good spirits and very energetic,” and is continuing to work, chief of staff Mark Meadows said outside the White House earlier in the day.

He spoke to reporters from a distance but without wearing a mask.

“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,” the White House said in a formal announcement.

Concerns are increasing that a large event held by Trump at the White House on Saturday may have spread the coronavirus.

Two senators, a university president, and ex-Trump adviser Kellyanne Conway, all announced Friday that they had tested positive after attending the event at the White House Rose Garden to announce Trump’s nominee for the U.S. Supreme Court.

The timeline indicates the president was already infected on Thursday when he attended a fundraiser in New Jersey.

He also held an outdoor rally in Minnesota on Wednesday.

Vice President Mike Pence has tested negative, and the White House physician said he does not need to quarantine.

Democratic presidential nominee Joe Biden wished the Trumps “a swift recovery.”

Biden was on stage with the president on Tuesday for the first presidential debate but has so far tested negative for the virus.

Trump, 74, who is known for his boisterous campaign rallies is now confined to the hospital as his campaign events are postponed or going virtual while Biden continues to campaign.

Wearing a face covering and giving an outdoor speech in Michigan on Friday, Biden urged the public to wear masks in public, saying it would save tens of thousands of lives.

“Be patriotic. It’s not about being a tough guy. It’s about doing your part,” Biden said, while offering his prayers for the Trump family.

Trump is often seen in public without a mask, which the White House has justified by saying the president practices social distancing and that his close contacts are regularly tested.

Stocks were down at close in New York, as markets digested both the president’s diagnosis and fresh jobs numbers, which suggest the economic recovery is slowing.

The initial news about Trump’s health came just after midnight, hours after he had already said he would quarantine because senior adviser Hope Hicks was confirmed to have contracted the virus.

It remains unclear when exactly Trump learned of Hick’s diagnosis and his spokeswoman, Kayleigh McEnany refused to provide details when pressed during an interview on Fox News.

“I’m not going to get into an exact timeline,” McEnany said.

More than 7 million people in the U.S. have tested positive for the virus, with the country one of the hardest hit by the pandemic.

More than 207,000 people have died.

Speaker of the House Nancy Pelosi criticized Trump’s recent public behaviour on the coronavirus, particularly on face coverings, while expressing hope for a “saner approach” to the pandemic from the administration.

She encouraged wider mask-wearing among the public.

The positive test result comes weeks before the November 3 election.

The president has been aggressively campaigning, holding regular rallies often in airport hangars, which are outdoors, but also hosting indoor fundraisers.

This is a crucial period for his campaign. Trump is trailing Biden in the polls, with a significant deficit that goes beyond the margin of error in some cases.

A significant issue weighing on the president’s campaign is a perception that he has mishandled the pandemic.

It is unclear whether the next presidential debate, due in less than two weeks, will take place