U.S. President Donald Trump and his wife, Melania, have tested positive for COVID-19.

President Trump announced their diagnoses via Twitter on Friday, writing, "We will begin our quarantine and recovery process immediately. We will get through this together."

Trump is 74 years old, putting him at higher risk of serious complications from a virus that has now killed more than 200,000 people in the United States.

Tonight, @FLOTUS and I tested positive for COVID-19. We will begin our quarantine and recovery process immediately. We will get through this TOGETHER!

— Donald J. Trump (@realDonaldTrump) October 2, 2020

Trump's positive test comes just hours after the White House announced that senior aide, Hope Hicks, came down with the virus.

Hicks travelled with the president multiple times this week, including aboard Marine One, the presidential helicopter, and on Air Force One to a rally in Minnesota Wednesday, and aboard Air Force One to Tuesday night's first presidential debate in Cleveland.

The diagnosis marks a major blow for a president who has been trying desperately to convince the American public that the worst of the pandemic is behind them even as cases continue to rise with less than four months before Election Day. And it stands as the most serious known public health scare encountered by any sitting American president in recent history.

Yet Trump had consistently played down concerns about being personally vulnerable to contracting COVID-19, even after White House staff and allies were exposed and sickened.

"I felt no vulnerability whatsoever," he told reporters back in May.

He has instead encouraged governors to reopen their states and tried to focus the nation's attention on efforts to revive the economy — not a growing death toll — as he seeks another four-year term.

The president has been reluctant to practise his own administration's social distancing guidelines for fear of looking weak. He continued to shake hands with visitors long after public health officials were warning against it and has refused under almost all circumstances to wear a mask in public.

Trump shares a video message from hospital following his COVID-19 diagnosis.

President Donald Trump has shared a video message to his personal Twitter account from hospital. This is the first time that he has spoken on camera to the world since the diagnosis, and he made a point to thank the medical staff appointed to him and Melania for taking good care of them.

“I came here, wasn’t feeling so well. I feel much better now. We’re working hard to get me all the way back,” Trump explained in the four minute long video. 

pic.twitter.com/gvIPuYtTZG

— Donald J. Trump (@realDonaldTrump) October 3, 2020

Many have asked questions around what Trump's diagnosis means for his presidential campaign, so Trump was quick to address this by saying, “I’ll be back, I think I’ll be back soon. And I look forward to finishing up the campaign the way it was started”. 

Although Trump's camp have worked hard to project an image of a president largely unaffected by the coronavirus, the president did acknowledge in his video that the next few days would be critical for him.

“You don’t know over the next period of a few days, I guess that’s the real test,” he said. “So we’ll be seeing what happens over those next couple of days.”

More to come.

- With AAP.