US President Donald Trump and his wife Melania have both tested positive for Covid-19.

It's being labelled a "Code Red" for the US government.

CNN's national security analyst Samantha Vinograd says this may be the most dangerous moment the US government has ever faced.

She says the President of the United States is suffering from the deadly virus, will have to quarantine, and isn't able to fully perform his duties as Commander-in-Chief.

Samantha Vinograd says, based on the number of people Trump comes into contact with every day without wearing a mask, it's logical other senior personnel within the national security apparatus could be infected as well.

Trump announced the news on Twitter, saying he and the First Lady would begin their quarantine and recovery process immediately.

"We will get through this together," he said.

The couple went into quarantine and got tested today after one of the President's closest advisers, Hope Hicks, contracted the infection.

In a memorandum, the President's physician said the President and First Lady "are both well at this time" and "plan to remain at home within the White House during their convalescence."

"Rest assured, I expect the President to continue carrying out his duties without disruption while recovering," he added.

Trump had announced earlier in an interview with Fox News that he and the First Lady were awaiting their results.

Trump said it was a difficult for him and those close to him to avoid the virus since so many others, including members of the military, try to interact with them.

"It's very hard when you're with soldiers, when you are with airmen, when you're with the Marines, and the police officers, I'm with them so much. And when they come over to you, it's hard to say, 'stay back, stay back.' You know, it's a tough kind of a situation, it's a terrible thing," he said.

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 just weeks before the November 3 election. And it stands as the most serious known public health scare encountered by any sitting American President in recent history.

Symptoms of Covid-19 can include fever, cough and breathing trouble. Most people develop only mild symptoms. But some people, usually those with other medical complications, develop more severe symptoms, including pneumonia, which can be fatal.

In an interview with Fox News host Sean Hannity earlier today, Trump said he was awaiting results of a Covid-19 test. "Whether we quarantine or whether we have it, I don't know," he said, adding that First Lady Melania Trump was also awaiting results.

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 on Wednesday, and aboard Air Force One to Tuesday night's first presidential debate in Cleveland.

Hicks, a former White House communications director who returned to the administration as a counsellor to Trump earlier this year, travelled to and from this week's presidential debate in Cleveland, Ohio with him.

She was also aboard the President's helicopter, Marine One, for a trip to Joint Base Andrews yesterday. And she was aboard Air Force One for Trump's visit to Minnesota, where he held a political rally.

Speaking to Fox News host Sean Hannity after his test, but before the result was known, Trump was in a fairly positive mood.

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 said told reporters 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 news was sure to rattle an already shaken nation still grappling with how to safely reopen while avoiding further spikes. The White House has access to near-unlimited resources, including a constant supply of quick-result tests, and still failed to keep the President safe, raising questions about how the rest of the country will be able to protect its workers, students and the public as businesses and schools reopen.

Trump is not the only major world leader known to have contracted the virus. British Prime Minister Boris Johnson spent a week in the hospital, including three nights in intensive care, where he was given oxygen and watched around the clock by medical workers. German Chancellor Angela Merkel self-isolated after a doctor who gave her a vaccination tested positive for the virus, and Canadian Prime Minister Justin Trudeau worked from home after his wife fell ill.

- In addition with AP and news.com