The White House has defended the US President’s astonishing motorcade drive-by after drawing criticism from a top medic, who described the outing as a moment of “insanity”.

White House spokesperson Judd Deere said “appropriate precautions” were taken as Donald Trump – who confirmed late on Thursday (local time) that he had COVID-19 – left the presidential suite at Walter Reed National Military Medical Centre, accompanied by Secret Service agents on Sunday.

“Appropriate precautions were taken in the execution of this movement to protect the President and all those supporting it, including PPE. The movement was cleared by the medical team as safe to do,” Mr Deere said.

Infected and contagious – and one month out from the presidential election – Mr Trump ventured from his sick bed in a motorcade to salute cheering supporters, eager to project strength despite his illness.

The move disregarded precautions meant to contain the deadly virus that has forced his hospitalisation and killed more than 209,000 Americans.

The President surprised supporters who had maintained a vigil outside the hospital since he was admitted late last week, driving by in a black SUV with the windows rolled up.

Secret Service agents inside the vehicle wore masks and other protective gear.

The driveby came New Jersey officials said they had contacted 206 guests who were at a campaign fundraiser at the Trump National Golf Course in Bedminister, just hours before the President announced he had COVID-19.

They have been asked to monitor for symptoms and, if they were close to Mr Trump or his staff, to quarantine for 14 days.

Kellyanne Conway who tested positive to the virus after the Rose Garden ceremony is seen speaking to Attorney-General Bill Barr. Photo: AAP

More than 20 people who attended a gathering in the White House Rose Garden for Mr Trump’s introduction of Judge Amy Coney Barrett as his nominee for the Supreme Court have now tested positive to the virus.

The event was highly social, but not distanced.

In the days that followed, a succession of attendees reported they had also contracted COVID-19. They included senators Mike Lee and Thom Tillis, former counsellor to the president, Kellyanne Conway and former New Jersey Governor Chris Christie.

On Monday (Australian time), Ms Conway’s daughter, Claudia, confirmed on social media that she also had the virus.

Several Secret Service agents accompanied the President. Photo: AAP

In a video posted to Twitter minutes before the drive-by, Mr Trump said he had “learned a lot” about the virus since his hospitalisation.

But one medical professional inside the hospital questioned whether Mr Trump had really learned anything.

“They might get sick. They may die. For political theater. Commanded by Trump to put their lives at risk for theatre. This is insanity.”

“Every single person in the vehicle during that completely unnecessary presidential ‘drive-by’ just now has to be quarantined for 14 days,” Dr James Phillips, an attending physician at Walter Reed, tweeted.

“For political theatre,” the doctor added. “Commanded by Trump to put their lives at risk for theatre.”

Former White House communications director Anthony Scaramucci took to Twitter to say the “stunt” showed a “total disregard for the health of the secret service and their families”.

“You lack intelligent messaging and leadership,” he wrote.

And CNN’s medical analyst and ER physician Leana Wed said “If [Trump] were my patient, in unstable condition + contagious illness, & he suddenly left the hospital to go for a car ride that endangers himself & others” she would call security to “restrain him then perform a psychiatric evaluation to examine his decision-making capacity.”

Supporters cheer and wave flags as Mr Trump’s motorcade passes. Photo: AAP

Trump declares he now ‘gets’ the virus

In the Twitter video, Mr Trump declared, “I get it,”.

“It’s been a very interesting journey. I learned a lot about COVID,” Mr Trump said, standing in his hospital room wearing a dark suit, no tie and an open-necked white shirt. “I learned it by really going to school.”

He added, “I get it, and I understand it.”

Earlier, his doctors sidestepped questions about exactly when his blood oxygen dropped – an episode they neglected to mention in multiple statements the day before – or whether lung scans showed any damage.

It was the second straight day of obfuscation from a White House already suffering from a credibility crisis after differing reports about exactly when he tested positive to the coronavirus.

One staffer told The Hill: “I’m not going to give you a detailed readout with timestamps every time the President’s tested. He’s tested regularly and the first positive test he received was after his return from Bedminster”.

But it raised more doubts about whether the doctors treating the president were sharing accurate, timely information with Americans about the severity of his condition.

Pressed about conflicting information he and the White House released on Saturday, Navy Commander Dr Sean Conley acknowledged he had tried to present a sunnier description of Mr Trump’s condition.

“I was trying to reflect the upbeat attitude that the team, the President, that his course of illness has had,” he said.

“Didn’t want to give any information that might steer the course of illness in another direction,” Dr Conley said.

“In doing so, you know, it came off that we were trying to hide something, which wasn’t necessarily true.”

Medical experts said Dr Conley’s revelations were hard to square with his talk of a discharge.

“There’s a little bit of a disconnect,” said Dr Steven Shapiro, chief medical and scientific officer at the University of Pittsburgh Medical Center.

According to CDC guidelines, “in general, transport and movement of a patient with suspected or confirmed SARS-CoV-2 infection outside of their room should be limited to medically essential purposes”.

-with agencies