Once again, the world shuddered at news about President Trump. This time, it wasn’t something Mr. Trump said or did, but rather the announcement that he had tested positive for the coronavirus.
Mr. Trump is not the first world leader to be infected. Prime Minister Boris Johnson of Britain and President Jair Bolsonaro of Brazil both tested positive. And Mr. Johnson suffered a serious bout of Covid-19, ending up in an intensive care unit where, he said later, “things could have gone either way.”
But Mr. Trump, 74, is older and at higher risks than either of those men. The news of an American president contracting a potentially lethal virus carried global repercussions beyond that of any other world leader. Financial markets fell in Asia and looked set to open lower in Europe and the United States.
Expression of concerns and good wishes for Mr. Trump’s speedy recovery — as well as that of first lady Melania Trump — poured in from leaders in India, Britain and other countries.
“Wishing my friend @POTUS @realDonaldTrump and @FLOTUS a quick recovery and good health,” the prime minister of India, Narendra Modi, said in a tweet.
Britain’s housing secretary, Robert Jenrick, said, “All of us want to send our best wishes to President Trump, the first lady and the Trump family and wish them a speedy recovery.”
“We know what it’s like to have, in our case a prime minister who tested positive for Covid and setting aside politics we all want to see him and his wife get better soon,” Mr. Jenrick said on Sky News.
Some foreign commentators, however, took note of Mr. Trump’s cavalier handling of the pandemic, saying it was a grim reminder of a virus that drew on distinctions between rich or poor, weak or powerful.
Others suggested a degree of justice in his diagnosis, given his record of diminishing the threat of the virus, refusing simple precautions like wearing a face mask and holding campaign rallies without social distancing.
“When the president of the United States, the most powerful person in the world, can catch this, the virus has no boundaries,” said Wang Huiyao, the founder and president of the Center for China and Globalization, an influential research group in Beijing.
WASHINGTON — President Trump said early Friday that he and the first lady have tested positive for the coronavirus, throwing the nation’s leadership into uncertainty and escalating the crisis posed by a pandemic that has already killed more than 207,000 Americans and devastated the economy.
Mr. Trump received the test results after one of his closest advisers, Hope Hicks, became infected, bringing the virus into his inner circle and underscoring the difficulty of containing it even with the resources of a president. Mr. Trump has for months played down the severity of the virus and told a political dinner just Thursday night that “the end of the pandemic is in sight.”
Mr. Trump’s positive test result could pose immediate difficulties for the future of his campaign against former Vice President Joseph R. Biden Jr., his Democratic challenger, with just 33 days before the election on Nov. 3. Even if Mr. Trump, 74, remains asymptomatic, he will have to withdraw from the campaign trail and stay isolated in the White House for an unknown period of time. If he becomes sick, it could raise questions about whether he should remain on the ballot at all.
Even if he does not become seriously ill, the positive test could prove devastating to his political fortunes given his months of diminishing the seriousness of the pandemic even as the virus was still ravaging the country and killing about 1,000 more Americans every day. He has repeatedly predicted the virus “is going to disappear,” asserted that it was under control and insisted that the country was “rounding the corner” to the end of the crisis. He has scorned scientists, saying they were mistaken on the severity of the situation.
Mr. Trump has refused for months to wear a mask in public on all but a few occasions and repeatedly questioned their effectiveness while mocking Mr. Biden for wearing one. Trailing in the polls, the president in recent weeks increasingly held crowded campaign events in defiance of public health guidelines and sometimes state and local governments.
Global markets dropped early Friday after President Trump said that he and Melania Trump, the first lady, had tested positive for the coronavirus.
Futures markets that track stocks in the United States signaled that Wall Street would open more than 1.5 percent lower.
European futures suggested markets there would open similarly lower. Yields on United States Treasury bonds fell too, as did futures tracking crude oil prices.
The news throws the political leadership of the world’s largest economy into doubt. It also raises questions about his campaign for re-election against former Vice President Joseph R. Biden Jr., his Democratic challenger. The election is set for Nov. 3, a little more than a month away.
In Japan, where the news broke late on the trading day, stocks finished nearly 0.8 percent lower after spending most of the day in positive territory. Most other Asian markets were closed for autumn holidays.
Television news networks leapt into breaking news mode early Friday morning, rousing anchors and correspondents from their beds as the nation began to absorb the news about President Trump and the first lady.
Sanjay Gupta, chief medical correspondent at CNN, was asleep when the news broke. Within minutes, he was broadcasting live through a home video link. Ali Velshi took over the anchor chair on MSNBC.
On Fox News, the host Sean Hannity, a close confidant of Mr. Trump, dialed in to declare the president “strong” and “healthy.” An overnight anchor, Ashley Strohmier, later told Fox News viewers of the president: “He obviously does not sleep. The man works 24/7. He’s up, I feel, like every hour of the day.”
Mr. Trump’s former doctor, Ronny Jackson, called into Fox News and sought to downplay concerns about Mr. Trump’s health.
“I bet you he does not develop symptoms,” Dr. Jackson said. “This does not become a big deal.”
The Secret Service sustained a coronavirus outbreak in August at its training facility in Maryland, evidence of just how close the pandemic has been to President Trump in the weeks before he was infected.
At least 11 employees at the center in rural Maryland tested positive for the virus even after it was closed for several months to mitigate transmissions, according to officials briefed on the matter.
Some of the personnel are believed to have contracted the virus during training exercises or at a graduation celebration at a nearby hotel where participants did not practice social distancing, the people said.
The agency declined to discuss the specifics of the outbreak, but it said in a statement that it “has taken significant precautions at its training center to protect the health and welfare of its trainees and training staff.”
The details about the problem at the center were uncovered by the Project on Government Oversight, an independent watchdog group in Washington. The organization brought the information about the outbreak to The New York Times, which independently confirmed details of it with people briefed on the matter. Those people spoke on the condition of anonymity because they did not want to be identified discussing delicate personnel matters.
The news early Friday morning that the president and the first lady had tested positive for the coronavirus gave the Secret Service outbreak new relevance. Hours before that announcement, the White House confirmed that Hope Hicks, a close adviser to Mr. Trump, had been infected.