President arrives at White House, removes mask and salutes

In a tweet announcing the move, Trump wrote, "Don't be afraid of Covid."

President Donald Trump's condition is continuing to improve as he fights a coronavirus infection, doctors said, and he left Walter Reed Medical Center on Monday evening, landing at the White House shortly before 7 p.m.

Doctors also reported that Trump, over the course of exhibiting coronavirus symptoms, had earlier experienced two episodes of "transient drops" in his oxygen saturation.

Yet the president was feeling well enough Sunday evening to briefly leave Walter Reed for a surprise drive-by, waving to supporters outside the hospital.

Administration member Judd Deere subsequently put out a statement saying that, "President Trump took a short, last-minute motorcade ride to wave to his supporters outside and has now returned to the Presidential Suite inside Walter Reed."

Meanwhile, numerous questions remain about how many people at the highest levels of government had been exposed to the virus after a week of events involving the president where social distancing and mask-wearing were lax in the White House and elsewhere.

Trump campaign fundraising off president’s exit from Walter Reed

The Trump campaign is already fundraising off of President Trump's exit from Walter Reed Medical Center Monday night, urging supporters not to be, "afraid of Covid," which has killed over 200,000 Americans.

The subject of a fundraising email sent Monday night said: "I'M BACK" -- even though his doctors said earlier in the day that he's not out of the woods yet.

The email goes on to argue "under the Trump Administration, we have developed some really great drugs and knowledge," but since testing positive the president has received some of the best treatment in the world -- which most Americans don't have access to.

"This is it...I need you to step up to the front lines during this critical time," the email urges supporters.

--ABC News' Will Steakin

Biden hits back at Trump’s tweet telling Americans not to let COVID-19 ‘dominate your life’ 

Former Vice President Joe Biden slammed Trump's tweet telling Americans, "don't let (coronavirus) dominate your life."

Biden responded in an interview with Local 10 News in South Florida shortly before the president left Walter Reed for the White House.

"President's getting out, I saw a tweet he did, they showed me," Biden said. "They said, 'don't let COVID control your lives.' Tell that to the 205,000 families who lost somebody."

President Trump "is essentially asking to be rehired, and the number one job he's had to do in the eyes of Americans is manage this pandemic -- and his own workplace is a contagion," said ABC News Senior National Correspondent Terry Moran.

Trump arrives at the White House, takes off his mask 

Marine One landed on the White House South Lawn at 6:53 p.m. Trump, again, did not stop and talk to reporters but made a dramatic return without speaking a word.

He, instead, walked up the steps of White House, faced the cameras and took off his mask -- in an apparent effort to project strength and flout public health protocols as he continues to battle COVID-19. Trump also gave a thumbs up and an extended salute to Marine One, before walking inside the residence.

The president is returning to a White House plagued by COVID-19 as 18 people in Trump's orbit have reported testing positive since last week.

Multiple White House sources told ABC News there is "a full-blown freak-out" in the administration waiting to see who will be next to test positive -- with aides not trusting each other and some trying to find ways to avoid coming into work.

Trump departing Walter Reed for White House

After spending three nights in the hospital, Trump is departing Walter Reed Military Medical Center in Bethesda, Maryland, en route to the White House, despite not having completed his full COVID-19 treatment.

Trump -- in a mask -- surrounded by Secret Service -- walked out of the hospital at 6:38 p.m. ET and waved to reporters as he entered a vehicle to take him to Marine One.

He did not answer shouted questions from the press on the health of his staff.

The president tweeted shortly before his departure that he "Will be back on the Campaign Trail soon!!!"

Earlier in the day, the president’s physician said he supported Trump's move to the White House but also acknowledged the president is “not necessarily out of the woods yet” and that he is on “uncharted territory” in terms of his treatment.

Guidelines from the Center for Disease Control and Prevention say that transporting a patient “outside of their room should be limited to medically essential purposes.”

Trump arrived on Friday evening after announcing at 12:54 a.m. on Twitter that he had tested positive for COVID-19.