US President Trump is "doing very well" and is up and moving about as he undergoes treatment for Covid-19, according to his medical staff, but a top White House officials says next 48 hours critical.

White House doctor Sean Conley says President Trump is not on oxygen or taking hydroxychloroquine.
White House doctor Sean Conley says President Trump is not on oxygen or taking hydroxychloroquine. (Reuters)

US President Donald Trump went through a "very concerning" period on Friday and the next 48 hours will be critical in terms of his care as he battles the coronavirus at a military hospital, White House chief of staff Mark Meadows has said.

Meadows comments on Saturday came after it was revealed that Trump was administered supplemental oxygen on Friday morning at the White House before he was transported to the hospital, although his medical staff insisted he had only mild symptoms.

Trump's doctors, for their part, painted a rosy picture of the president's health in a press conference at Walter Reed National Military Medical Center. But the briefing by Navy Commander Dr Sean Conley and other doctors raised more questions than it answered.

"The team and I are extremely happy with the progress the President has made," Conley said.

Trump's medical staff said he is not on oxygen or taking hydroxychloroquine. 

Conley also said Trump has started treatment with Remdesivir, a drug known to help patients recover from the virus while refusing to reveal whether the president had ever been on oxygen, despite repeated questioning. 

Later on Saturday, Conley said Trump is free of fever and improving but is not yet out of danger.

"He spent much of the afternoon conducting business, and has been up and moving about the medical suite without difficulty," Conley said in a statement.

Trump's symptoms including cough and nasal congestion "are now resolving and improving," his health staff said. "He's in exceptionally good spirits," said another doctor, Sean Dooley.

Trump released a new hospital video in which he says he’s starting to feel better and hopes to “be back soon.”

In the four-minute video, Trump says he “wasn’t feeling so well” when he was admitted to the hospital on Friday after testing positive for the coronavirus.

But he says that “I feel much better now” and that “We’re working hard to get me all the way back.”

US first lady Melania Trump is also "doing great" and has no indications for hospitalisation, doctors added.

Presidential race upended

Trump is staying at a military hospital for treatment after testing positive for Covid-19, an extraordinary development that has upended the presidential race a month before the November 3 election.

New cases also emerged among some of his top advisers and allies. 

Roughly 17 hours after he made his diagnosis public, Trump walked slowly from the White House to a waiting helicopter to be taken to Walter Reed National Military Medical Center in Bethesda, Maryland. 

He wore a mask and business suit and did not speak to reporters.

"I think I'm doing very well, but we're going to make sure that things work out," Trump, 74, said in a brief video message posted on Twitter.

Trump will work in a special suite at the hospital for the next few days as a precautionary measure, White House press secretary Kayleigh McEnany said.

Trump had no public events scheduled on Saturday.

A number of other prominent Republicans have tested positive, including former White House senior adviser Kellyanne Conway and Republican Senators Mike Lee and Thom Tillis.

On Saturday, a third senator was diagnosed with Covid-19: Republican Ron Johnson, chairman of the Senate Homeland Security Committee.

Former New Jersey governor Chris Christie checked himself into a hospital as a precautionary measure after testing positive for the virus.

READ MORE: Trump joins growing list of world leaders testing positive for coronavirus

Experimental treatment  

On Friday, Dr Conley said the president felt fatigued and that he had been given an experimental treatment aimed at staving off a severe case of Covid-19.

Earlier, Trump was given an experimental antibody drug that's currently in late-stage studies from Regeneron Pharmaceuticals Inc.

Dr Conley also said the president had been given remdesivir at the military hospital.

READ MORE: Trump's Covid-19 post deleted by Twitter and Facebook over misinformation

Unpredictable virus

"The odds are far and away that he’ll have a mild illness" as most people with the virus do, said Dr Gregory Poland, an infectious disease specialist at the Mayo Clinic who has no role in Trump’s care.

But Covid-19 is very unpredictable, he stressed.

"We have young people who die. We have nursing home patients, a lot of them, who actually do quite well," Poland said.

READ MORE: Too little, too late? Trump embraces masks in about-face

Signs and symptoms

Coronavirus infection causes mild or no symptoms in about 80 percent of cases. About 15 percent of people become seriously ill and 5 percent get critically ill.

Symptoms, when they do occur, usually appear two to 14 days after infection and can include loss of smell or taste, coughing, a sore throat, trouble breathing, fatigue, muscle or body aches, headache, nausea or vomiting, diarrhea, and fever.

Up to half of the patients who are hospitalised don't have a fever when admitted but nearly all develop one. How people fare varies widely, some seem to be recovering and then suddenly worsen.

Pneumonia, often with a specific appearance on X-rays, sometimes develops but complications in virtually every organ of the body have been reported.

Doctors also increasingly recognise that some people have long-lasting symptoms.

Trump's risks

Older age, being male, and having any other health problems increase the chance of severe illness, and Trump has those.

At 74, "his age would be the primary risk factor", said Dr David Banach, an infectious disease physician at the University of Connecticut's health system.

People ages 65 to 74 are seven times more likely to be hospitalised for Covid-19 than those who are 18 to 29 years old, according to the US Centers for Disease Control and Prevention. 

The risks rise exponentially at older ages.

Trump also is obese, with a body mass index just past 30.

"Obesity is a state of chronic lowered immunity. In other words, you don’t respond to vaccines as well, you don’t respond to infections as well” as people of normal weight, Poland said.

Trump takes a statin drug to lower his cholesterol, and that condition also raises his risk for Covid-19 complications, doctors said.

READ MORE: US President Trump and first lady test positive for Covid-19

Next steps

Doctors likely will check Trump often for any difficulty breathing, coughing or other symptoms, Banach said.

No drugs are known to help for people with no or very mild symptoms. 

Remdesivir and steroids have shown benefit for certain moderately and severely ill patients and remdesivir is now being tested for patients in the early stages of Covid-19.

Antibodies are proteins the body makes when an infection occurs. 

They attach to a virus and help it be eliminated. 

The Regeneron drug is made with purified versions of two such antibodies.

READ MORE: What you need to know about Covid-19 vaccines in the works

Risk to others

Could Trump have infected Democratic presidential nominee Joe Biden during the debate Tuesday night?

Possible, but not likely, experts said. 

The candidates were almost two metres apart. 

But both candidates, especially Trump, spoke loudly, which research suggests can make virus particles travel farther, Poland said.

Biden said on Friday that he and his wife, Jill, tested negative.

'This is a wake up call'

Dr George Abraham, who heads the infectious disease board for the American Board of Internal Medicine, warned that "a negative test doesn’t guarantee that someone is not harbouring virus" because there might be too little to detect early in infection.

"This is a wake up call" that shows the need for social distancing, wearing masks, and other measures to reduce spread, Abraham said.

Biden similarly tweeted, "I hope this serves as a reminder: wear a mask, keep social distance, and wash your hands."

A myriad of other people who have been around Trump in the previous 48 hours are at risk, doctors said.

"Contact tracing is going to be really important," Banach said. "The president comes into contact with many individuals during the day."

READ MORE: Trump, Biden push into crucial first 2020 campaign face-off

Source: TRTWorld and agencies