The period between infection and illness can range from a few days to two weeks, so he could have contracted it repeatedly and in various people.
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Here is a summary of some of the people involved so far:
Donald Trump, 74 ans
US President since 2016, he has seen his campaign effectively suspended after testing positive for COVID-19.
He was at the Rose Garden of the White House on Saturday September 26 to announce the appointment of Justice Amy Coney Barrett to the Supreme Court. He attended a rally in Pennsylvania on Saturday night and another event in Ohio on Monday.
He was at a fundraiser and rally in Minnesota on Wednesday, where he gave a shorter speech than usual.
On Thursday morning, Mr. Trump was said to have learned of the positive test result for Hope Hicks. Despite this, he organized a fundraising trip to his New Jersey golf club. According to public health guidelines, he should have isolated himself, having been near a person infected with the virus.
In the early hours of Friday, after returning from the New Jersey event, he tweeted to say that he and his wife had tested positive and were in isolation.
Hope Hicks, 31 ans
Presidential adviser and former director of communications for the White House. She is a close confidante of Mr. Trump.
Ms Hicks was not at the Rose Garden event on September 26.
She was part of the team that traveled with Mr Trump to Cleveland for the presidential debate on Tuesday. She returned a negative test Wednesday morning and joined others for the trip to Minnesota that day. It was in Minnesota that she said she felt bad.
She stayed away from the others on the first leg of the trip (by plane) and did not bring the crowded Marine One back to the White House. Thursday morning, his test was positive. Those who were near her were not immediately informed.
Melania Trump, 50 ans
First Lady, wife of Donald Trump.
She often travels with her president husband and she was at the Rose Garden event in late September.
Her diagnosis was announced at the same time as that of her husband on Friday October 2.
She tweeted later in the day that she was experiencing “mild symptoms” and that she “felt good overall,” adding, “I look forward to a speedy recovery.
Kellyanne Conway, 53
Former presidential adviser who left the White House in August.
She was at the Rose Garden event on Saturday, seated in the front row.
Photos from the event showed a few hundred people sitting next to each other, many without masks, including Ms Conway.
She tweeted: “My symptoms are mild (mild cough) and I feel fine. “
Senator Mike Lee, 49
Republican from Utah, Mr. Lee was also at the Rose Garden last Saturday and met with Amy Coney Barrett, who was announced as Mr. Trump’s choice for the vacant seat on the United States Supreme Court, days more late.
He announced he tested positive for COVID-19 on Friday, after testing negative earlier in the week.
Senator Thom Tillis, 60
Republican of North Carolina and member of the Judiciary Committee.
He tested negative before attending the White House Rose Garden event on Saturday and met with Mr. Trump’s Supreme Court candidate Ms. Coney Barrett on Wednesday. Mr Tillis was pictured wearing a mask at Saturday’s event, but not at Wednesday’s meeting.
On Thursday night, he took part in a debate with Democratic challenger for his Senate seat, Cal Cunningham. Both wore masks.
Mr Tillis revealed his positive test result on Friday. Mr Cunningham said he was going to be tested.
John Jenkins, 65 ans
President of the University of Notre Dame, Mr. Jenkins is another person who was at the Rose Garden event last Saturday and who announced his positive test result on Friday.
University vice-president Paul Browne said in a statement that Jenkins had “learned that a colleague he was in regular contact with has tested positive for COVID-19.”
Bill Stepien, 42 ans
The president’s campaign manager has also tested positive for the coronavirus and is experiencing “mild flu-like symptoms.”
Mr. Trump’s immediate campaign events have all been called off and his next debate with Democrat Joe Biden, scheduled for October 15, is now in question.
The trio tested positive on Friday after spending last weekend at the White House or traveling with Mr. Trump, according to Zeke Miller, president of the White House Correspondents Association.
Joe Biden, 77 years old
A Democratic presidential candidate, Mr. Biden debated Tuesday with Mr. Trump in Cleveland.
Unlike Mr. Trump, Mr. Biden regularly wore a mask in public. However, during the exchanges, he did not wear one.
Many in the audience, including members of Mr. Trump’s family, were also not wearing masks.
Mr Biden and his wife Jill tested negative on Friday.
Kamala Harris, 55 ans
Vice-presidential candidate Mr Biden’s running mate took a routine test and the result was negative on Thursday.
Amy Coney Barrett, 48 ans
Mr. Trump’s Supreme Court candidate was at the Rose Garden event on September 26 to accept her Supreme Court nomination.
She recovered from a confirmed case of coronavirus earlier this year.
Mike Pence, 61 ans
The US Vice President and his wife Karen tested negative Friday morning.
Mr Pence was reportedly in the Oval Office with the President on Tuesday and was last seen publicly with him at a press conference on Monday.
William Barr, 70 ans
The U.S. Attorney General was at the Rose Garden event on September 26 and was seen without a mask, speaking with Ms Conway, but tested negative on Friday, a Department of Justice spokesperson said.