Around the same time, Trump tweeted: "Going well, I think! Thank you to all. LOVE!!!"
Trump's diagnosis -- followed by his move to Walter Reed, where the White House said he plans to stay and work for "the next few days" -- presented the most serious known health threat to the US presidency since former President Ronald Reagan was non-fatally shot in 1981.
The decision to take Trump to the hospital marked a sharp turn from the statement Conley made early Friday when he first confirmed the Covid-19 diagnosis of Trump and first lady Melania Trump, and said the couple would remain at the White House during their convalescence.
Wearing a suit and mask, Trump, who's 74, gave a low-key wave to the press but took no questions as he walked without assistance across the South Lawn of the White House to Marine One, the helicopter that airlifted him to the hospital. He left for Walter Reed after receiving a dose of the experimental medical treatment Regeneron -- which may have signaled a rising level of concern among his physicians, Dr. Jonathan Reiner, CNN medical analyst and professor at George Washington University, told CNN on Friday.
Though White House staff claimed the President made the move "out of an abundance of caution," there were still more questions than answers about the President's condition on Friday, in part because of the consistent lack of transparency from this White House and the fact that his physicians have not briefed the press, which has been typical protocol when past presidents have faced health concerns.
White House officials underscored that the President has not transferred power to Vice President Mike Pence, as is sometimes customary when a president is ill or scheduled to undergo a procedure that could require anesthesia.
The President "is in charge," a White House communications aide said Friday, and Trump released a short recorded video on Twitter thanking his supporters for their well wishes as he arrived at Walter Reed shortly before 6:30 p.m. ET.
"I want to thank everybody for the tremendous support. I'm going to Walter Reed Hospital. I think I'm doing very well," Trump said in the 18-second video, which was notable for its brevity. "We're going to make sure that things work out. The first lady is doing very well. So thank you very much, I appreciate it. I will never forget it. Thank you."
Melania Trump remained at the White House with what the White House physician described as a mild cough and a headache.
But her husband's age, his sex and the fact that he is clinically obese put him at greater risk of complications from the virus. It was unclear exactly when the couple was tested and how long they could have been contagious.
The incubation period for the virus is estimated to be anywhere between five and 14 days, according to the US Centers for Disease Control and Prevention, and the agency's guidelines say that anyone exposed to the virus should quarantine for 14 days.
A pattern of dismissing the virus
Following the same recklessness the President has shown throughout the pandemic, Trump decided to go to a campaign fundraiser in Bedminster, New Jersey, Thursday evening even though he had learned before the trip that Hicks, one of his senior aides who had traveled with him throughout the week, had tested positive for the virus.
The President not only traveled earlier in the week to the first presidential debate with Biden, who tested negative on Friday, but he also attended several campaign rallies over the past week.
There are increasingly troubling signs from the White House events last Saturday when Trump and the first lady hosted a sizable crowd in the Rose Garden as the President announced the nomination of Judge Amy Coney Barrett to the Supreme Court. Guests did not socially distance and very few wore masks. At least seven people, including the President and first lady, have tested positive. University of Notre Dame President the Rev. John Jenkins, Conway and Republican Sens. Mike Lee of Utah and Thom Tillis of North Carolina, who were seated relatively close to each other, tested positive.
Lee was seen on video hugging other attendees. Barrett and her husband contracted the virus earlier this summer and recovered, according to three sources familiar with the matter.
Conway, Stepien and Hicks were all involved in the President's preparations for his debate with Joe Biden on Tuesday. Coronavirus symptoms can appear within two to 14 days of exposure, but most often develop with four to five days.
A longstanding credibility gap
The lack of information about the severity of Trump's illness Friday night was complicated by the fact that the President and his allies have downplayed the dangers of Covid-19 ever since the virus reached the US.
Trump and members of his administration already faced a major credibility gap because of their extensive history of putting out false or misleading information about a variety of topics over the past four years, including the severity of the pandemic and the risks to public health.
The descriptions of the President's condition shifted throughout the day Friday -- and much of the early information about his well-being was reported by the press first and then confirmed by the White House, underscoring the lack of transparency from this administration.
On Friday morning, as the White House tried to project a business-as-usual demeanor, chief of staff Mark Meadows described Trump as energetic. But later in the day, Conley, the doctor intimately involved in Trump's care, wrote in a memo that he was "fatigued." And CNN learned from another source that the President had a fever for much of the day.
In the afternoon memo, Conley said Trump was given the Regeneron polyclonal antibody cocktail, an experimental drug that has not yet been approved by the Food and Drug Administration. Trump's doctor also said he is taking zinc, vitamin D, famotidine, melatonin and a daily aspirin.
"As of this afternoon the President remains fatigued but in good spirits," his physician wrote. "He's being evaluated by a team of experts, and together we'll be making recommendations to the President and First Lady in regards to next best steps."
Within a few hours, Trump was headed to Walter Reed.
Dr. Leonard Schleifer, the CEO of biotechnology company Regeneron, told CNN's Wolf Blitzer that Trump would have received the experimental antibody treatment that his company manufactures to help boost his immune system, which he said is now in "a race" against the virus.
"If the virus wins you can have dire consequences, obviously, and what our antibodies do is we make it a fair fight," Schleifer said on CNN. "He's in a higher risk group for a variety of reasons, such as being older, and if we give our antibodies, we hope that we will give his immune system enough of a boost so that he can win this and make a complete recovery."
An inevitable outcome
The President's cavalier attitude toward the virus, his decision to keep traveling and holding large rallies, and the fact that he discouraged mask use by most Americans until late this summer made his eventual diagnosis all but inevitable -- given how he has practiced behaviors that his own coronavirus task force has discouraged to the public.
As recently as this week's presidential debate in Ohio, Trump mocked Biden for wearing a mask. In prerecorded remarks for Thursday night's Al Smith charity dinner, the President proclaimed that the "end of the pandemic is in sight."
He has continually undercut and contradicted the advice of his top medical experts as he has flouted public health guidelines by holding events with few masks and people in close proximity to one another, putting his supporters and their contacts at risk.
And as he tries to win reelection, Trump has insisted, in contradiction to the statistics and statements of the nation's top infectious disease experts, that the US is rounding the corner in its fight against Covid-19, stating that it is time for Americans to get back to work and children back to school. He has falsely argued that Biden wants to shut down the country instead of opening it back up, citing that as a reason why Americans should reelect him.
Throughout the spring and summer, both Trump and his aides continually answered questions from the press about why the President refused to wear a mask by insisting that he and the people around him are tested for coronavirus on a daily basis.
But many medical experts have pointed out that testing only offers a snapshot of one's diagnosis at a moment in time and that it may have given White House staffers -- and the President -- a false sense of security as aides continually showed up for work at the White House not wearing masks.
At the debate this week, the President's children arrived wearing masks, but took them off during the event.
On Friday evening, Trump's son Eric made it clear in a tweet that this was no ordinary situation as he called his father a "true warrior" and asked the President's supporters to join him in prayers.
"He will fight through this with the same strength and conviction that he uses to fight for America each and every day. I ask you to join me in praying for his recovery," Eric Trump said on Twitter. "I have never been more proud of someone and what they have had to endure."