adds extraordinary drama to an already fast-moving and tumultuous election campaign.
It is likely to have a destabilising effect in the US and around the world.
On Saturday, after spending his first night at a military hospital, Mr Trump said he was “feeling much better" and that he’d be “back soon”.
There are a number of questions still unanswered, but here's a summary of what we know so far:
Where is he now?
Mr Trump will just outside Washington to undergo treatment, but will continue to work, the White House said on Friday.
The president's campaign manager Bill Stepien said on Friday that all previously announced campaign events ahead of the 3 November election would be held virtually or postponed.
Mr Stepien has since tested positive to the virus, according to a senior campaign official, as reported by Reuters.
Marine One lifts off from the White House to carry President Donald Trump to Walter Reed National Military Medical Center Source: AP
What treatment is he receiving?
White House physician Sean Conley said on Friday evening that the president was "doing very well" in hospital and was not requiring any supplemental oxygen.
He was first given a single dose of Regeneron Pharmaceutical's experimental antibody cocktail, Dr Conley said in a letter earlier on Friday. The is being studied in four late-stage clinical trials but hasn't yet received any form of regulatory approval.
He has also been given at least two doses of remdesivir, an intravenous antiviral drug, and has been taking zinc, vitamin D, famotidine, melatonin and a daily aspirin.
As a 74-year-old man, Mr Trump is "at higher risk for severe illness" from the virus, according to US health agency CDC.
Mr Trump is being monitored closely for the wide range of common symptoms, which include fever, chills, cough, shortness of breath, fatigue, muscle ache and headache.
What are his symptoms?
On Thursday, Mr Trump did not immediately isolate after his close aide Hope Hicks tested positive.
Instead, he boarded a plane to New Jersey, where he attended a fundraiser at his golf club and delivered a speech surrounded by dozens of people before returning to the White House.
The New York Times quoted unnamed sources saying Mr Trump showed mild symptoms at the Thursday night event, seeming lethargic. One source told the paper he had displayed cold-like symptoms.
As he arrived at the hospital on Friday, Mr Trump said in a video posted to Twitter he was "doing very well”.
During a briefing on Mr Trump's condition on Saturday, Dr Conley said the president was not receiving extra oxygen and still "doing very well".
Dr Conley said Mr Trump had been fever-free for 24 hours and his symptoms, including a cough and nasal congestion, were "resolving and improving".
However, a source familiar with Mr Trump's health, named by multiple US media outlets as his chief of staff Mark Meadows, .
"The president's vitals over the last 24 hours were very concerning and the next 48 hours will be critical in terms of his care," the source told White House pool reporters on Saturday. "We're still not on a clear path to a full recovery."
In a video posted to Twitter a few hours later, Mr Trump said he was “feeling much better". He also thanked the medical professionals looking after him and said he thought he’d be “back soon”.
“This [diagnosis] was something that happened, and it’s happened to millions of people all over the world, and I’m fighting for them … We’re going to beat this coronavirus, or whatever you want to call it, and we’re going to beat it soundly,” he said.
In a written update issued on Saturday night, Dr Conley said Mr Trump had been making "substantial progress" and his medical team remained "cautiously optimistic".
How did he get it?
It is unknown how Mr Trump contracted the coronavirus, but he has defied medical advice by seldom wearing a mask and often meeting with large groups of people.
White House alarm bells started to ring when Ms Hicks tested positive. She is a central figure in Mr Trump's inner circle and travelled with him several times over the last week.
She was also closely involved in his preparations for Tuesday's debate against Democrat Joe Biden. At the televised event, many of Mr Trump's guests did not wear masks.
Questions are also being asked about where Mr Trump announced his nomination of Judge Amy Coney Barrett to the Supreme Court.
A crowd watches on at the White House Rose Garden last week as Donald Trump announces Amy Coney Barrett as his nominee to the Supreme Court Source: AP
Former White House adviser Kellyanne Conway attended the event and tested positive on Friday, along with Republican senators Mike Lee and Thom Tillis and University of Notre Dame President John Jenkins.
The senators sit on the chamber's Judiciary Committee, which is slated to hold confirmation hearings for Judge Barrett.
Who else around Mr Trump has it?
Vice President Mike Pence, who would step in if Mr Trump falls seriously ill, tested negative on Friday, as did Mr Trump's teenage son Barron.
Ivanka Trump and Jared Kushner, the president's daughter and son-in-law who are top White House advisers, also tested negative, as well as Secretary of State Mike Pompeo, Treasury Secretary Steven Mnuchin and Health and Human Services Secretary Alex Azar.
Mr Biden and his presidential running mate Kamala Harris also tested negative, their campaign said on Friday.
Those confirmed on Friday to have tested positive included Ms Hicks, Ms Conway, Mr Stepien, Mr Lee, Mr Tillis and chair of the Republican National Committee Ronna McDaniel.
On Saturday, Chris Christie, a former New Jersey governor who is now a campaign adviser for Mr Trump and also attended the Rose Garden event, tested positive as well.
The latest is one of the president's personal assistances, Nick Luna, who tested positive after having travelled with Mr Trump several times recently, a White House official who requested anonymity confirmed on Saturday night.
Several White House journalists have also returned COVID-positive tests.
Additional reporting by AFP, Reuters.
