US President Donald Trump has made a theatrical return to the White House to continue his treatment for coronavirus after a three-night hospital stay.
Mr Trump, who is still contagious, removed his mask on the balcony of the White House, while posing for pictures.
His physician said he would continue treatment from there, and he "may not entirely be out of the woods yet".
Several of Mr Trump's staff and aides have also tested positive for the virus in recent days.
Questions remain over the seriousness of Mr Trump's illness after a weekend of conflicting statements.
On Tuesday, his first morning back in the White House, the president took to Twitter to compare Covid-19 to the flu.
"Flu season is coming up!" he wrote. "Are we going to close down our Country? No, we have learned to live with it, just like we are learning to live with Covid."
The US remains the country worst-hit by Covid-19, with 210,000 deaths and 7.4 million cases. Between 1 October 2019 and 4 April 2020, the flu caused between 24,000 and 62,000 deaths in the US, according to government figures.
Mr Trump's diagnosis has upended his campaign for a second term in office, less than a month before the Republican president faces Democratic challenger Joe Biden in the presidential election.
What happened during Trump's return?
Wearing a navy business suit, tie and mask, Mr Trump walked out of Walter Reed National Military Medical Center in the Washington DC suburbs on Monday evening pumping his fist.
After a short helicopter ride, Mr Trump was pictured alone on the Truman Balcony of the White House. He removed his protective face mask, before giving a thumbs-up and a military-style salute.
A couple of hours later, he tweeted a campaign-style clip of his return set to stirring music.
Mr Trump also recorded a video message, urging Americans to get back to work.
"You're going to beat it [coronavirus]," he told them, adding: "We're going to be out front. As your leader, I had to do that. I knew there's danger to it, but I had to do it. I stood out front, and led."
Mr Trump also speculated: "Now I'm better, maybe I'm immune, I don't know".
The World Health Organization says it is too early to know if people who have recovered from Covid-19 are protected from a second infection, and if so, how long this protection might last. The president's own medical team does not consider him to be fully recovered yet.
Mr Trump also promised that vaccines were "coming momentarily", although the US Centers for Disease Control has said no vaccine is expected to be widely available before the middle of next year.
Before leaving hospital, the president told Americans in a tweet not to fear the disease and said he would be back on the campaign trail "soon".
Democratic presidential nominee Joe Biden said he was "glad" the president appeared to be "coming along pretty well".
But he criticised Mr Trump, saying: "Anybody who contracts the virus by essentially saying masks don't matter, social distancing doesn't matter, I think is responsible for what happens to them."
According to US public health guidelines, Mr Trump should remain in isolation for up to 10 days after symptoms first appear. The White House says the president first started to appear ill on Thursday evening, and later tested positive.
An almost messianic message
Analysis box by Anthony Zurcher, North America reporter
Donald Trump says he has overcome the coronavirus - and you can, too.
In his video message from the White House, a mask-less Trump tells the American public: "Don't be afraid of it. You're going to beat it."
And so the president's message in the final weeks of his re-election campaign takes shape. He contracted the coronavirus because he was an out-front leader and he "had to do that".
"Nobody that's a leader would not do what I did," he said.
It is a message almost messianic in its undertones - one that the rest of his party is amplifying. The president has suffered and overcome, and will lead the nation to a promised land beyond the virus.
New York Post columnist Miranda Devine, quote-tweeted by the president, said Mr Trump would return to the campaign trail as an "invincible hero". Georgia Senator Kelly Loeffler tweeted out a video of Mr Trump tackling a virus-headed antagonist.
There is political and personal risk for the president, of course. He could experience a relapse or long-term medical difficulties. Americans who have lost loved ones to the disease may find his words and actions ill-considered or offensive.
The president, however, seems determined to turn his recent weakness into a strength.
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What did Trump's doctors say?
His physician Sean Conley said on Monday afternoon that the president, whose oxygen levels dipped twice over the weekend, would be "surrounded by world-class medical care 24/7" at the White House.
He refused to answer questions about when Mr Trump last received a negative test or to go into the specifics of his treatment. He would not offer details regarding the president's scans to check for pneumonia, citing patient protection laws.
He did confirm Mr Trump is still on the steroid dexamethasone and has received three doses of antiviral drug remdesivir. He was to receive another before discharge and a fifth at the White House.
When asked about whether Mr Trump was safe to travel for campaign events, Dr Conley said: "We'll see."
"If we can get through to [next] Monday with him remaining the same or improving, better yet, then we will all take that final deep sigh of relief," he added.
What the doctors will be looking out for
Analysis box by Michelle Roberts, health editor
Considering we're told President Trump tested positive on Thursday, he seems to be making great progress - especially as he is a high risk patient, being 74, a man, overweight and living with a heart condition. He's received a cocktail of drugs normally reserved for the sickest of Covid patients who have been ill for weeks, not days, to aid and hasten his recovery.
It's not clear when Mr Trump caught the virus or first started to feel unwell. Most people who develop symptoms do so on around day five. Some people have only mild symptoms that clear up after a week or so with some bed rest.
A turning point can be around seven days later, with some patients getting a more serious lung infection from the virus. These patients need to be in hospital because they can deteriorate quickly and need expert care. The body can go into overdrive fighting the virus, leading to respiratory failure, septic shock and multiple organ damage.
Mr Trump's doctors say they remain cautiously optimistic about the president's health but "on guard" for at least the coming week should things take a turn for the worse.
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What's the latest with the White House outbreak?
The president's discharge comes as more new cases have been reported among White House staff.
Press secretary Kayleigh McEnany became the latest high-profile figure close to the president to confirm a positive test earlier on Monday.
US media said two other aides to the press secretary had had positive results. Ms McEnany was seen speaking to journalists without wearing a mask on Sunday but said no members of the press had been listed as close contacts by the White House medical unit.
First Lady Melania Trump, senior aides and several Republican senators have also tested positive.
Mrs Trump, who is 50, has been isolating at the White House, reportedly with mild symptoms. In a tweet she said: "I am feeling good [and] will continue to rest at home".
At least 12 people close to Mr Trump have now tested positive, as have several junior staff members.
Many of those attended a gathering at the White House Rose Garden on 26 September that is being scrutinised as a possible "super-spreader event".
Among them is former New Jersey Governor Chris Christie, who said on Saturday he had checked himself into hospital because he is asthmatic, a known high-risk factor.
The latest coronavirus case to emerge from that event, at which the president unveiled his nominee for the US Supreme Court, is a Christian minister from California.
Pastor Greg Laurie, who is said to have mild symptoms, was also with US Vice-President Mike Pence earlier in that day at a prayer march in central Washington DC.
Plexiglass will be used to separate Vice-President Mike Pence and Democratic challenger Kamala Harris and limit the risk of Covid transmission when they go head-to-head in a debate in Salt Lake city, Utah, on Wednesday. Both candidates have recently tested negative.