President Donald Trump’s coronavirus diagnosis comes after a busy week running his administration and campaigning ahead of the 3 November election, during which time he has interacted with many high-level officials.
The president announced positive test results for himself and his wife, Melania, in a tweet on Friday, at around 01:00 local time (05:00 GMT).
This followed a positive diagnosis for his close aide, Hope Hicks, who reportedly started feeling symptoms on Wednesday and tested positive the next day.
It takes five days on average from the moment a person is infected for symptoms to start showing, but it can be much longer, so the World Health Organization advises a 14-day isolation period.
The peak infectious period for the virus is the day before symptoms appear and the two days after, although a large proportion of people never show any symptoms at all.
The White House says it has begun contact-tracing. Here is a look at some of the people we know Mr Trump has crossed paths with in the last week.
Saturday, September 26: The Supreme Court pick
President Trump announced his Supreme Court pick, Judge Amy Coney Barrett, in front of a crowd of about 200 people on the White House lawn.
On Saturday evening, President Trump held a rally at Harrisburg International Airport in Middletown, Pennsylvania.
Since the afternoon’s ceremony, Judge Coney Barrett has held meetings with various senators - including Senate Majority Leader Mitch McConnell - ahead of her much-anticipated confirmation hearing, which is due to take place on 12 October.
Judge Coney Barrett said on Friday that she had tested negative. Sources told US media she had the virus earlier this year.
Several people who attended the Rose Garden event for her announced on Friday they had tested positive.
They include former White House counsellor Kellyanne Conway and Senator Mike Lee of Utah and Senator Thom Tillis of North Carolina, who are both on the judiciary committee, and the president of the University of Notre Dame, John Jenkins. It is unknown when they caught it.
Sunday, September 27: Golf and a veterans’ event
The president played golf at his club in Potomac Falls, Virginia, on Sunday morning and led a White House reception for the families of military veterans in the evening.
Monday, September 28: The Covid briefing
On Monday, President Trump held a news briefing - giving an update on his administration’s coronavirus testing strategy - in the White House Rose Garden.
It was attended by Vice-President Mike Pence, Health Secretary Alex Azar, Education Secretary Betsy DeVos, and the chief executive of Abbott Laboratories, Robert Ford, among others.
Also on Monday, Trump viewed a model of a new pickup truck - being built at a factory in Ohio - on the White House lawn. Representatives from the company, Lordstown Motors, attended, as well as two members of Congress.
The White House regularly tests officials who come in contact with the president. However, US media has noted that mask-wearing and social distancing around him is less common, suggesting that people may be too reliant on the testing system, which is not foolproof.
Tuesday, September 29: Debate day
The president faced his election rival, Joe Biden, at their first face-to-face debate in Cleveland, Ohio on Tuesday evening.
President Trump flew there on his presidential plane, Air Force One, alongside his wife, adult children and multiple aides. Many were seen not wearing masks when boarding or disembarking, according to US media reports.
Also on the plane were: White House Chief of staff Mark Meadows; campaign strategist Jason Miller; policy adviser Stephen Miller; Robert C O’Brien, the national security adviser who tested positive for the virus in July; and Ohio Congressman Jim Jordan.
After landing, the president’s campaign manager, Bill Stepien, was spotted getting into a staff van with Ms Hicks, the New York Times reports. Late on Friday, it was announced that Mr Stepien had tested positive for Covid-19 and was experiencing mild flu-like symptoms.
The debate was held at Cleveland Clinic’s Health Education Campus, a shared facility with Case Western Reserve University.
The organisers, the Commission on Presidential Debates, brought in numerous Covid-era safety precautions. There were no handshakes between the two candidates and everyone attending - including the 80 or so audience members - was tested before the event and asked to wear masks throughout.
In the run-up, Mr Trump’s eldest daughter, Ivanka, posted a picture of herself backstage in a mask, alongside her sister Tiffany, sister-in-law Lara and stepmother Melania.
However, during the event itself, Ivanka Trump and other family members, including siblings Don Jr and Eric, were pictured mask-less. Moderator Chris Wallace has since told Fox News that they were offered masks by event staff but they waved them away.
Don Jr told Fox News on Friday he had tested negative.
Observers said those on Mr Biden’s side of the room kept their masks on.
Mr Trump and Mr Biden kept a distance during the debate, at podiums on opposite sides of the stage.
When the candidates were greeted by the wives on stage afterwards, Jill Biden wore a mask and Melania Trump didn’t.
At a separate campaign event in Pennsylvania on Tuesday, Vice-President Mike Pence said he had been in the Oval Office with President Trump earlier that day. It is thought to be their last in-person meeting. On Friday, Mr Pence said he and his wife Karen Pence had tested negative, as have Mr and Mrs Biden.
President Trump and much of his entourage flew back to Washington DC on Tuesday night.
Wednesday, September 30: A fundraiser and a rally
The day after the debate, President Trump was straight back into campaign business, flying to Minnesota. Ms Hicks was among those accompanying him.
He attended a closed-door fundraiser at a private home in Minneapolis, and he later held a large rally in at an airport in Duluth, in front of a crowd of thousands. Few wore masks but there was distance between them and the president.
Minnesota Congressman Kurt Daudt tweeted a picture of himself close to Mr Trump, with neither wearing masks.
On Wednesday evening, Mr Trump and various aides returned to Washington DC on Air Force One again.
Ms Hicks, who was feeling unwell, was isolated in a separate cabin, according to US media. She reportedly disembarked from the back of the plane, instead of the front alongside the other passengers.
Thursday, October 1: More fundraising
President Trump flew to his Bedminster golf resort in New Jersey for a private fundraiser.
Several aides who were in proximity to Ms Hicks scrapped their plans to accompany the president, according to the Associated Press.
Kayleigh McEnany, the White House press secretary, who is thought to have been in close contact with Ms Hicks, held a briefing for reporters at the White House on Thursday, without mentioning her colleague’s test and without wearing a mask. She has since said she did not know about the diagnosis.
That night, in pre-taped remarks to the annual Al Smith dinner in New York City, held virtually this year, he said that “the end of the pandemic is in sight”.
Mr Trump later announced in a phone evening interview on Fox News that he and the first lady were being tested for the virus.
Though it is not known how many of his supporters he came into contact with in recent days, he told Fox presenter Sean Hannity that people were always wanting to get close to him. “They want to hug you, and they want to kiss you,” he said.
Friday, October 2: The announcement
President Trump announced that he and Mrs Trump had tested positive around 01:00 on Friday in a tweet, adding that they will begin the “quarantine and recovery process immediately”.
Just before 11:00, his chief of staff, Mark Meadows, told reporters the president has “mild symptoms” but remains in “good spirits”.
Mrs Trump tweeted to say she also had mild symptoms.
So far, the vast majority of released test results have been negative. No-one can be sure who caught the virus first among these leading US political figures and their relatives, or who passed it to whom, or where they caught it.
A negative test usually means a person does not have Covid-19.
However, test accuracy can vary depending on when a sample is taken during the course of the illness, and one taken very soon after exposure may not give an accurate result.
Hope Hicks, president’s adviser - positive
Donald Trump, president - positive
Melania Trump, first lady - positive
Former White House counsellor Kellyanne Conway - positive
Joe Biden, presidential candidate - negative
Jill Biden, wife of Joe Biden - negative
Mike Pence, vice-president - negative
Karen Pence, second lady - negative
Kamala Harris, vice-presidential candidate - negative
Doug Emhoff, husband of Kamala Harris - negative
Amy Coney Barrett, Supreme Court nominee - negative
Mike Lee, Utah senator on judiciary committee - positive
Thom Tillis, North Carolina senator on judiciary committee - positive
Mike Pompeo, secretary of state - negative
Steve Mnuchin, treasury secretary - negative
Alex Azar, secretary of health and human services - negative
William Barr, attorney general - negative
Ivanka Trump, president’s daughter - negative
Jared Kushner, president’s son-in-law - negative
Donald Trump Jr - negative
Bill Stepien, president’s campaign manager - positive