Donald Trump has “mild symptoms” but is in “good spirits” after contracting coronavirus, a White House official has said.
The president and his wife Melania are self-isolating after testing positive for COVID-19, just one month before the US election.
His election rival Joe Biden – who took part in a televised debate with the president earlier this week – confirmed he has tested negative for the virus, along with his wife.
The Democratic presidential candidate wrote on Twitter: “I’m happy to report that Jill and I have tested negative for COVID. Thank you to everyone for your messages of concern. I hope this serves as a reminder: wear a mask, keep social distance, and wash your hands.”
White House chief of staff Mark Meadows told reporters on Friday that the president and first lady “remain in good spirits” but confirmed Mr Trump “does have mild symptoms”.
“He continues to be, not only in good spirits, but very energetic,” Mr Meadows said.
“I’m optimistic that he will have a quick and speedy recovery.”
Mrs Trump wrote on Twitter that she also has “mild symptoms” but is “overall feeling good”, adding: “I am looking forward to a speedy recovery.”
A White House official told NBC News that discussions are taking place about whether Mr Trump will address the American public later.
Campaign events being run by Mr Trump have now been moved online or have been postponed, according to his re-election team, as have ones involving his family.
However, Vice President Mike Pence, who has tested negative, “plans on resuming his scheduled campaign events.”
The president confirmed on Twitter that he and Mrs Trump have been diagnosed with COVID-19, saying: “We will begin our quarantine and recovery process immediately. We will get through this TOGETHER!”
The couple’s 14-year-old son, Barron, has tested negative and “all precautions are being taken to ensure he’s kept safe and healthy”, the first lady’s chief of staff Stephanie Grisham told NBC News.
World leaders offered messages of support, as did Mr Biden, who said he was sending his thoughts to Mr and Mrs Trump “for a swift recovery”.
“We will continue to pray for the health and safety of the president and his family,” Mr Biden said.
Prime Minister Boris Johnson, who spent time in intensive care with coronavirus in April, said: “I think we all want to send our best wishes to the president and the first lady.
“I’m sure that they’ll both stage a very strong recovery.”
Russian President Vladimir Putin also expressed his “sincere support” to Mr and Mrs Trump “in this difficult moment,” according to the Kremlin.
It said Mr Putin had sent a message which read: “I hope that your inherent vitality, good spirits and optimism will help you cope with the dangerous virus.”
Democratic House of Representatives Speaker Nancy Pelosi said she hoped Mr Trump’s diagnosis might be a “learning experience” about the virus and warned against “brazen” behaviour that allowed “something like this to happen”.
“Let us all pray for the president’s health,” she told MSNBC. “This is tragic, it is very sad.”
Mr Trump is 74 years old and his health records earlier this year showed he was categorised as obese, putting him at higher risk of serious complications from the virus.
He is now expected to self-isolate for two weeks while he receives treatment for the disease.
Mr Trump’s doctor, Sean Conley, said the president and first lady would remain at the White House during their period of isolation.
He said: “Rest assured I expect the president to continue carrying out his duties without disruption while recovering, and I will keep you updated on any future developments.”
Writing on Twitter, Mrs Trump said: “As too many Americans have done this year, (the president) & I are quarantining at home after testing positive for COVID-19.
“We are feeling good & I have postponed all upcoming engagements. Please be sure you are staying safe & we will all get through this together.”
Before testing positive, Mr Trump had said he and his wife were self-isolating after Hope Hicks, one of his top aides, had contracted the virus.
Ms Hicks, who serves as a counsellor to the president, is the closest aide to Mr Trump to test positive so far.
She had travelled with the president several times over the last week, including on presidential helicopter Marine One, and on Air Force One to Tuesday night’s first presidential debate.
Mr Meadows told reporters on Friday that it was discovered that Ms Hicks had tested positive for the virus “right as Marine One was taking off yesterday”.
US Vice President Mike Pence, Secretary of State Mike Pompeo, Mr Trump’s daughter Ivanka and his son-in-law and senior adviser Jared Kushner have all tested negative.
Mr Trump’s positive test come as the virus continues to spread at an alarming rate in the US, even as the president has tried to downplay the threat of the disease.
More than 200,000 people have died in the US after contracting COVID-19 and more than seven million people have been infected.
But Mr Trump has continued to hold campaign rallies which have drawn thousands of supporters.
His diagnosis now throws into question the nature of the rest of the campaign, including the remaining two presidential debates.
The next debate is scheduled for 15 October in Miami.
Two days before testing positive, during the first debate, Mr Trump belittled his Democratic challenger Joe Biden for frequently wearing masks and not having campaign rallies that matched his own in size.
The president continued to shake hands with visitors despite public health officials warning against it and also initially resisted being tested.
Mr Trump also refused to wear a mask in public under almost all circumstances.