BETHESDA, Md. (NewsNation Now) — President Donald Trump’s physician Sean P. Conley reports improvement of Trump’s COVID-19 symptoms of mild cough, nasal congestion, and fatigue.

However, a source said the president went through a “very concerning” period Friday and the next 48 hours will be critical in terms of his care.

In a Saturday news briefing, Dr. Conley told reporters the president’s heart and kidney function is normal and he is “not on oxygen.” The Associated Press reports a person familiar with Trump’s condition said the president was administered supplemental oxygen on Friday at the White House.

President Donald Trump’s doctor says he is doing “very well” as he spends the weekend at a military hospital for treatment of COVID-19.

Conley said Trump has been fever-free for 24 hours as he updates the nation on the president’s condition from the hospital Saturday morning. Trump was admitted Friday after testing positive for the coronavirus.

“Just 72 hours into the diagnosis now, the first week of COVID, in particular days 7-10 days as the most critical in determining the likely course of this illness,” said Conley. “At this time, the team and I are extremely happy about the progress the president has made.”

Later Saturday, Conley clarified his previous statement.

“This morning while summarizing the President’s health, I incorrectly used the term “seventy two hours” instead of “day three” and “forty eight hours” instead of “day two” with regards to his diagnosis and the administration of the polyclonal antibody therapy. The President was first diagnosed with COVID-19 on the evening of Thursday, October 1st and had received Regeron’s antibody cocktail on Friday, October 2nd.”

While Conley said the president is not currently on oxygen, he refused to say whether the president had ever been on oxygen, despite repeated questioning. He said that Trump’s symptoms, including a cough and nasal congestion “are now resolving and improving.”

“He’s in exceptionally good spirits,” said another doctor, Sean Dooley. He said Trump told doctors, “I feel like I could walk out of here today.”

Conley provided another update on Trump’s condition Saturday evening, saying the president has completed a second dose of Remdesivir.

“President Trump continues to do well, having made substantial progress since diagnosis,” said Conley. “He remains fever-free and off supplemental oxygen with a saturation level between 96 and 98% all day.”

President Donald Trump arrived at Walter Reed National Military Medical Center late Friday following a positive coronavirus diagnosis.

Friday evening, Dr. Conley said President Trump is not requiring supplemental oxygen, but is now getting Remdesivir therapy.

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

Trump tweeted late Friday, “Going welI, I think! Thank you to all. LOVE!!!”

The president, wearing a mask, boarded Marine One at the White House, gave a thumbs up to the reporter pool and a short wave; he did not stop to talk. The president was walking normally on his own without any visible signs of difficulty. Marine One lifted off at 6:20 p.m. ET

TOPSHOT – US President Donald Trump gives a thumbs up as he walks to Marine One prior to departure from the South Lawn of the White House in Washington, DC, October 2, 2020, as he heads to Walter Reed Military Medical Center, after testing positive for Covid-19. – President Donald Trump will spend the coming days in a military hospital just outside Washington to undergo treatment for the coronavirus, but will continue to work, the White House said Friday (Photo by SAUL LOEB / AFP) (Photo by SAUL LOEB/AFP via Getty Images)

The White House Friday announced the president is moving into a special suite at the military medical center in Bethesda, Maryland for the next “few days” as a precautionary measure. A senior White House official tells NewsNation no transfer of power is expected; “the president is in charge.”

“President Trump remains in good spirits, has mild symptoms, and has been working throughout the day. 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. President Trump appreciates the outpouring of support for both he and the First Lady,” White House Press Secretary Kayleigh McEnany said in a statement.

Doctors urged the move so the president could receive immediate care if needed, a White House official said. The president was flown to Walter Reed via Marine One, the president’s helicopter.

Friday afternoon, Dr. Conley said “the President remains fatigued but in good spirits.”

President Trump received a received a single 8 gram dose of Regeneron’s investigational antibody cocktail, Dr. Conley said “as a precautionary measure,” in addition to zinc, vitamin D, famotidine, melatonin and a daily aspirin.

A spokesperson says Vice President Mike Pence, who tested negative for the virus along with his wife Karen, is at his official residence at the U.S. Naval Observatory in Washington as the White House prepares to transfer the president to Walter Reed. Pence is in good health, his spokesperson says. Pence is scheduled to host a campaign event in Arizona on Thursday.

While the full severity of Trump’s symptoms remain unknown, the positive test raises questions about what would happen if he were to become incapacitated due to the virus.

John Hudak, a senior fellow and deputy director at the Brookings Institution’s Center for Effective Public Management, outlined some of the scenarios designed to protect the continuity of government in the event of a positive COVID-19 test in a research note published in July.

“In an unfortunate scenario in which the president were to contract COVID-19 and need therapies such as a ventilator and/or the use of other therapies that would impair his cognitive abilities and/or abilities to communicate, there are a few procedures in place to deal with that situation,” Hudak said. For transparency, the Brookings Institute is a public policy nonprofit based in Washington, D.C.

Vice President Mike Pence, House Speaker Nancy Pelosi, Sen. Chuck Grassley (who is president pro tempore, third in line for the presidency), and members of the cabinet would all need to be isolated from the president, said Hudak.

If Trump’s treatment were to impair his ability to perform his duties, the president could invoke Section 3 of the 25th Amendment to the Constitution.

This would allow the vice president to become “acting president” until the president notifies the House and Senate that he is able to perform his duties once again.

President Ronald Reagan invoked Section 3 in 1985 and President George W. Bush did so twice in 2002 and 2007, all for medical procedures.

If Trump were to decline rapidly, ruling out the possibility of invoking Section 3, Hudak said Section 4 of the 25th Amendment would provide a solution to such a crisis.

In that scenario, the vice president and a majority of the cabinet would send notice to the House and Senate “that the President is unable to discharge the powers and duties of his office.” This would also see the vice president assume the role of acting president until the president recovers.

“While presidential incapacity would be a serious national situation, the government would be able to function in a largely uninterrupted way until the president is recovered,” Hudak said.

This is a developing story. Refresh for details.