Trump "is doing very well" Saturday morning, Dr. Sean Conley, physician to the president, said from Walter Reed Medical Center in Bethesda, Maryland. 

Trump is in “exceptionally good spirits” and is not having difficulty breathing or walking around, Conley said.

"He did have a fever Thursday into Friday and since Friday he's had nothing," Conley said, though he would not say how high Trump's fever was.

"The president's been fever-free for over 24 hours. We remain cautiously optimistic, but he's doing great," he added.

"We have monitored his cardiac function, his kidney function, his liver function, all of those are normal," Conley said.

Trump will be treated with a five-day course of Remdesivir.

"Thursday he had a mild cough with some nasal congestion and fatigue all of which are now resolving and improving," Conley said. "The team and I are extremely happy with the progress the president has made."

Pressed on whether the president had been treated with supplemental oxygen at any point since his diagnosis, Conley wouldn’t provide a clear, declarative answer.

“And you said he's not received any supplemental oxygen?” a reporter asked.

“He's not on oxygen right now, that's right," Conley said.

When the reporter followed up on whether he had at any point, Conley replied, “He’s not needed any this morning, today, at all.”

At one point, Conley said, "yesterday and today he was not on oxygen." In another answer later he said, "Thursday, no oxygen. None at this moment. And yesterday with the team while we were all here, he was not on oxygen." He did not address whether Trump had received oxygen while his team was not on site.

Asked whether Trump has experienced difficult breathing, Conley said, "No. No, he has not. Never did."

Reporters questioned when Trump last had a positive test, but Conley would not answer.

Conley also raised questions about the timeline by saying the president was "72 hours into the diagnosis," though Trump's diagnosis was announced to the public about 36 hours ago. Conley then in a memo sent by the White House said he "incorrectly used the term 'seventy two hours' instead of day three' and 'forty eight hours' instead of 'day two.'" Conley confirmed that Trump was diagnosed Thursday night.

Conley did not say when Trump would be discharged. "I don't want to put a hard date on that," Conley said.

This was Conley’s first on-camera briefing on the president’s condition.

ABC News' Elizabeth Thomas contributed to this report.

Former New Jersey governor and ABC News contributor Chris Christie, who helped Trump prep for Tuesday’s debate from the White House on Monday, tweeted Saturday morning, “I just received word that I am positive for COVID-19.”

“I will be receiving medical attention today and will keep the necessary folks apprised of my condition,” he wrote.

Christie is one of eight people who have tested positive after attending last weekend's event in the White House Rose Garden where Trump officially nominated Amy Coney Barrett to the Supreme Court.

While the president had experienced a shortness of breath after testing positive for the virus, Saturday morning he is not having difficulty breathing, sources familiar with the matter tell ABC News.

Trump went to Walter Reed Medical Center after experiencing a low-grade fever, chills, nasal congestion and cough. The president still has those symptoms on Saturday, multiple sources said. 

Trump rested well through the night as doctors continue to monitor and evaluate him through the weekend to determine when he can return to the White House, sources told ABC News. As of Saturday morning, the president was still feeling fatigued but was signing papers and working, the sources said. 

The president is still not considering any transition of power to Vice President Mike Pence. However, the president is worried, as coming down with the virus has spooked him and top aides, sources said.

White House Chief of Staff Mark Meadows, who stayed at Walter Reed with the president overnight, tested negative for COVID-19 again Saturday morning.

ABC News' Katherine Faulders and John Santucci contributed to this report.

Donald Trump Jr., who attended Tuesday’s debate with the president, tweeted Saturday that he’s tested negative.

"I'll give it a few more days out of and [sic] abundance of caution and test again and if I’m clear I’ll be back to work asap," he tweeted.

"Thanks to all those who so lovingly have reached out … It truly means a lot to us,” he added.

Now that the president's current campaign manager and a former top White House official have tested positive for COVID-19, attendance at Monday’s debate prep session at the White House has become a common denominator among many. 

Below is a list of who ABC News knows was in the room and their current status. 

IT WAS IN: The Map Room (with some aides moving to the Oval Office after) 

IT HAPPENED: Monday, Sept. 28 at midday

THE ATTENDEES:

President Donald Trump - POSITIVE 
Campaign Manager Bill Stepien - POSITIVE 
Former Senior Advisor Kellyanne Conway - POSITIVE
Counselor Hope Hicks - POSITIVE 
Senior Advisor Jared Kushner - NEGATIVE 
Personal Lawyer Rudy Giuliani - NEGATIVE 
Campaign Senior Advisor Jason Miller - NEGATIVE 
Senior Adviser Stephen Miller - TBD 
Former New Jersey Gov. Chris Christie - AWAITING RESULTS

Other aides potentially popped in over the course of the meeting which was in one room but lingered to the Oval Office. 

 ABC News' John Santucci, Katherine Faulders and Will Steakin