The Covid-19 crisis had already haunted Donald Trump's first term in office, as his scatter-gun response placed him increasingly at odds with the science. Then he tested positive, a month before the election.

The US president announced in the small hours of Friday that he and First Lady Melania Trump would be going into quarantine after they were both found to have contracted the novel coronavirus.

Hours earlier, Hope Hicks, one of his top aides who is also close to the first lady, had received news of her own positive test.

The coronavirus, which emerged late last year in China and early in 2020 in the US, has upended Donald Trump's presidency, casting him into a dangerous moment in his battle with Democratic rival Joe Biden over who will occupy the White House for the coming four years.

Trump first mentioned the new coronavirus in public on January 22, 2020, during a visit to the World Economic Forum in Davos, Switzerland.

"We have it totally under control. It's one person coming in from China. It's going to be just fine," he said at the time.

The populist Republican has consistently downplayed the threat posed by the pandemic, saying on numerous occasions that the virus would disappear as the weather warmed.

"Typically, it will go away in April," he said in February.

According to The Washington Post, which analyzed the president's statements, he said 34 times that the virus would disappear on its own.

Instead, the outbreak spread rapidly, forcing state governors and local authorities across the country to impose lockdowns.

By mid-March, the US had ground to a standstill, with schools closed and links to the rest of the world drastically reduced.

The economy soon collapsed and with it one of the president's main arguments for re-election.

During his first debate Tuesday with Biden, Trump maintained that he had built "the greatest economy in history." But he was harking back to pre-pandemic conditions that no longer hold.

Since the beginning of the crisis, Trump has promoted unproven remedies for Covid-19 such as hydroxychloroquine, an anti-malarial drug which doctors say has proved ineffective against the coronavirus.

US President Donald Trump, pictured at the White House in 2018, accuses the media of bias against him
US President Donald Trump, pictured at the White House in 2018, accuses the media of bias against him AFP / Jim WATSON

He backed the drug with the full force of the federal government, announcing on March 28 from the White House that it had been given emergency authorization.

Trump even announced at the end of May that he himself had embarked on a preventive course of the therapeutic.

"I'm taking it, hydroxychloroquine, right now, yeah. Couple of weeks ago, I started taking it," he declared.

The Food and Drug Administration's emergency approval would later be revoked, but Trump remained an ardent promoter of the treatment on the world stage.

The episode was emblematic of the president's confused messaging on the outbreak.

Amid the repeated promises of a vaccine, the far-fetched remedies and the rush to reopen the economy, Trump left the actual management of the fightback to individual states, dooming any chance of a unified national response.

In early April, health authorities recommended that masks be worn in an announcement at the White House that Trump immediately undercut by insisting he himself would not wear one.

The billionaire former reality TV star has even gone as far as piling mockery on those who do follow the advice to mask up, including Biden.

Trump didn't appear masked in public until July 11 but has rarely been seen covered up since.

He has been excoriated for his stewardship of a crisis that has so far led to almost 208,000 deaths in the United States, among 7.2 million registered cases.

The US -- home to less than five percent of the world's population -- is the worst-hit nation, accounting for more than 20 percent of the global death toll.

In stark contrast to the cautious, by-the-book Biden, who has spent much of the election season at home in Delaware, Trump decided to continue actively campaigning and has basked in large crowds of devoted supporters in a series of rallies.

He was in Minnesota on Wednesday. An event scheduled for Friday in Florida has been canceled, and appearances scheduled for Saturday in battleground state of Wisconsin look likely to fall be the wayside, too.

Tests carried out regularly on the 74-year-old president had so far come back negative.

Until his late night tweet when he made the announcement that stunned the world: "Tonight, @FLOTUS and I tested positive for COVID-19."