In addition, the Chair of the Republican National Committee, Ronna McDaniel, who was with Mr Trump a week ago, has tested positive, the party said on Friday.
Several cases have been confirmed among those who have had close contact with Donald Trump and his aide Hope Hicks, whose diagnosis prompted the test that confirmed the US president had the coronavirus.
The period between infection and sickness can be anything from a few days to two weeks, so he could have contracted it on a number of occasions and from a variety of people.
Here is a summary of some of those involved so far:
Positive tests:
Donald Trump, 74
US president since 2016, he has seen his campaign effectively put on hold after testing positive for COVID-19.
He was at the White House Rose Garden last Saturday 26 September to announce the nomination of Judge 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 on Wednesday in Minnesota, where he did a shorter speech than usual.
By Thursday morning Mr Trump would have been aware of the positive test result for Hope Hicks. Despite this, he went ahead with a fundraising trip to his golf club in New Jersey. According to public health guidelines he should have isolated, having been in close proximity to someone infected with the virus.
In the early hours of Friday, after returning from the New Jersey event, he tweeted to say he and his wife had tested positive and were in isolation.
Ms Hicks was not at the Rose Garden event on 26 September.
She was part of the team who travelled with Mr Trump to Cleveland for the presidential debate on Tuesday. She returned a negative test on Wednesday morning and joined others for the trip to Minnesota that day. It was in Minnesota that she reported feeling unwell.
She stayed apart from others on the first leg of the journey (by plane) and did not take the crowded Marine One back to the White House. On Thursday morning her test was positive. Those who had been near her were not immediately told.
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 her husband's on Friday 2 October.
She tweeted later in the day that she was experiencing "mild symptoms" and was "overall feeling good", adding: "I am looking forward to a speedy recovery."
Republican from Utah, Mr Lee was also at the Rose Garden last Saturday and met Amy Coney Barrett, who was announced as Mr Trump's pick for the vacant seat on the US Supreme Court, a few days later.
He announced he had tested positive for COVID-19 on Friday, after a negative result earlier in the week.
He had a negative test before attending the White House Rose Garden event on Saturday and he met Mr Trump's Supreme Court nominee Ms Coney Barrett on Wednesday. Mr Tillis was pictured wearing a mask at the Saturday event, but not at the Wednesday meeting.
On Thursday night he took part in a debate with the Democratic challenger for his senate seat, Cal Cunningham. Both wore masks.
Mr Tillis revealed his positive test result on Friday. Mr Cunningham has said he will get tested.
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.
The university's vice president Paul Browne said in a statement that Mr Jenkins had "learned that a colleague with whom he has been in regular contact tested positive for COVID-19".
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 cancelled, and his next debate with Democrat Joe Biden, scheduled for 15 October, is now in question.
Three journalists
The trio tested positive on Friday after spending last weekend at the White House or travelling with Mr Trump, according to Zeke Miller, president of the White House Correspondents' Association.
Merimental: ITK. am well aware of wat he meant. he's referring to Trump as a civilian who received a complement from d uniform guy b4 boarding Airforce1.
Oga av been through military, no be today
You see, you are wrong. Presidents have always received salutes because they are the commander in chief.
Donpenny: Quick recovery president. But civilian will always be a civilian how would you received a naval salute compliment from a naval officer with a naval salute without an head gear.
The practice began with Ronald Reagan. Reagan served in the military and he discovered that some of the troops were confused about when they should end their salute when saluting the president. Reagan discussed with the commandant of the Marine Corp and the commandant told him that as commander in chief he can return the salute if he feels like, so Reagan began returning the salute and every president since then has done the same.
It's true that it is military tradition that you do not salute if you are not wearing a head dress, but the presiedent almost never wears a head dress so that rule doesn't apply to him.
Merimental: As d Commander in Chief of The Armed Forces, he is due a complete complement from a uniform man even while in bed till he leaves d white house.
Oga na Oga. uniform is for d ppl working under him.
Analysis by Anthony Zurcher. North America reporter
The US presidential election has been turned on its head.
That sentence could have been written about any number of moments in a tumultuous year in American politics, but nothing quite like this has occurred this year, this decade, this century.
Just 32 days before the presidential election, Donald Trump has tested positive for Covid-19. Given his age, 74, he is in a high-risk category for complications from the disease. At the very least, he will have to quarantine while he is treated, meaning the US presidential contest - at least his side of it - has been fundamentally altered.
The initial implications are obvious. The president's rigorous campaign schedule - which included visits to Minnesota, Pennsylvania, Virginia, Georgia, Florida and North Carolina in just the past week - is on indefinite hold.
Trump will certainly have surrogates on the trail for him, but given that he has relied heavily on his family and senior administration and campaign officials for such tasks in the past, and many of them may have to quarantine because of their own exposure to the virus, that campaign operation will be disrupted as well.
What treatment has the president already received?
Mr Trump's physician Sean Conley said in a statement earlier on Friday that the president had "as a precautionary measure received an 8g dose of Regeneron's polyclonal antibody cocktail" at the White House.
The medication is administered to help reduce virus levels and speed recovery.
He was also taking zinc, vitamin D, famotidine, melatonin and aspirin, Dr Conley said.
"As of this afternoon he remains fatigued but in good spirits," he added. The first lady, who is 50, was "well with only a mild cough and headache".
On Friday afternoon, Mrs Trump said she was experiencing mild symptoms but is "feeling good" and "looking forward to a speedy recovery".
The remainder of the Trumps' family, including the first couple's son Barron who also lives at the White House, tested negative.
How have Democrats reacted?
Mr Biden, the Democratic nominee, and his wife Jill tested negative on Friday.
"I hope this serves as a reminder," the White House candidate tweeted after the result. "Wear a mask, keep social distance, and wash your hands."
The Biden campaign said it was in the process of temporarily taking down all its negative ads regarding Mr Trump.
Mr Biden's staff said he would travel to Michigan on Friday as planned for several campaign events. He and his wife have wished the presidential couple a speedy recovery.
Speaking at a virtual campaign event for Mr Biden, former President Barack Obama also extended well wishes to Mr and Mrs Trump.
"We're all Americans and we're all human beings and we want to make sure everybody is healthy," he said.
Speaker of the House Nancy Pelosi said that her prayers for Mr Trump have "intensified" after she learned of positive coronavirus test, and that she hopes his diagnosis will be "a learning experience" for the country.
Mrs Pelosi, who is third in the presidential line of succession, was not notified in advance that the president would be taken to hospital, according to CBS.
Since the onset of the pandemic, Democrats have criticised the president for flouting basic health guidelines, such as social distancing and wearing a facial covering in public - including those promoted by his own administration. Mr Trump has also continued to hold large campaign rallies, gathering thousands of supporters, often without masks.
It is not known how exactly Mr and Mrs Trump became infected. On Thursday, the first couple said they intended to self-isolate after one of Mr Trump's closest aides, Hope Hicks, tested positive. Soon afterwards, they too received positive test results.
There has been criticism of Mr Trump's decision to go to a fundraiser attended by dozens of people in New Jersey on Thursday, apparently when officials already knew about Ms Hicks' symptoms.
Officials said the process of tracking all the president's contacts in recent days was ongoing, adding that Mr Trump was considering how he might address the nation or otherwise communicate with the American people on Friday.
Republican National Committee Chairwoman Ronna McDaniel, who was with Mr Trump a week ago, has tested positive, the party said on Friday. Two US senators, Mike Lee and Thom Tillis, who were recently in the president's orbit too, were also confirmed on Friday to have tested positive.
Both of them attended Mr Trump's unveiling of his Supreme Court nominee, Judge Amy Coney Barrett, at the White House last Saturday.
Judge Coney Barrett tested positive for coronavirus earlier this year but has since recovered, according to unnamed officials quoted by the Washington Post.
Several top White House aides have already tested positive in recent months for the virus including the vice-president's press secretary, Katie Miller, National Security Adviser Robert O'Brien and one of Mr Trump's personal valets.
US President Donald Trump has been flown to hospital less than 24 hours after testing positive for coronavirus.
The White House said the decision to transport him to Walter Reed National Military Medical Center was taken "out of an abundance of caution".
Mr Trump - who had a fever - said early on Friday he and First Lady Melania Trump had tested positive for Covid-19.
The White House said he was feeling "fatigued but in good spirits" and was experiencing mild symptoms.
The news comes just over a month before presidential elections, where he will face Democratic challenger Joe Biden.
How did the president look on Friday?
Wearing a mask and suit, Mr Trump walked out across the White House lawn on Friday afternoon to his helicopter, Marine One, for the short trip to hospital.
He waved and gave a thumbs-up to reporters but said nothing before boarding the aircraft.
In a video posted to Twitter, Mr Trump said: "I want to thank everybody for the tremendous support. I'm going to Walter Reed hospital. I think I'm doing very well.
"But we're going to make sure that things work out. The first lady is doing very well. So thank you very much, I appreciate it, I will never forget it - thank you."
The president's children, Ivanka and Eric, retweeted his post, praising him as a "warrior". Ms Trump added: "I love you dad."
Upon arrival at Walter Reed, the president did not go to the emergency room for treatment, but went directly to the hospital's presidential suite, according to the BBC's US partner, CBS News.
What is the White House saying?
White House press secretary Kayleigh McEnany said in a statement: "President Trump remains in good spirits, has mild symptoms, and has been working throughout the day.
"Out of an abundance of caution, and at the recommendation of his physician and medical experts, the president will be working from the presidential offices at Walter Reed for the next few days.
"President Trump appreciates the outpouring of support for both he and the first lady."
Mr Trump's symptoms include a low-grade fever, according to CBS.
Walter Reed, in the Washington DC suburbs, is one of America's largest and most renowned military medical centres. It is where US presidents usually go for their annual check-ups.
White House communications director Alyssa Farah said the president had not transferred his powers to Vice-President Mike Pence.
"The president is in charge," she said.
But he pulled out of a video conference call with vulnerable seniors scheduled for Friday, leaving Mr Pence to chair the meeting.
Under the US constitution, if Mr Trump did become too ill to carry out his duties, he could hand over his powers to the vice-president temporarily. That means Mike Pence would become acting president until Mr Trump was fit again and could resume work.
SAMBARRY: if he's truly infected how come bieden and those around him aren't infected?
Actually at least three people around him have become infected. In fact, the first announcement that was made this morning was that his senior aide had been infected. I guess it was that revelation that led to another test for Trump and his wife.
President and Mrs Trump announced that they had tested positive for COVID-19 and there was some concern that former vice president, Joe Biden and Dr Jill Biden might have also caught the disease due to Joe Biden's close proximity to Donald Trump at the presidential debate. See previous thread here.
Joe Biden has now announced that they have tested negative for the disease.
Joe Biden @JoeBiden
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.
Guzman101: Na which kind lie be this Guy your imformation is not correct donald trump and his wife are both in quarantine still awaiting their test result after his councillor tested positive to the deadly virus
Foreign Affairs › Re: President Trump Develops Fever, Flown To Walter Reed Hospital by naptu2(op): 12:23pm On Oct 03, 2020
