Donald trump and his wife melania have tested positive for covid-19 and will quarantine barely a month before the us presidential election.

Tonight, and i tested positive for covid-19. we will begin our quarantine and recovery process immediately. we will get through this together! mr trump tweeted.

Shortly after mr trump sent the tweet, the white house released a signed memorandum from the presidents physician confirming that both mr and mrs trump had tested positive for coronavirus on thursday evening.

The president and first lady are both well at this time, and they plan to remain home at the white house during their convalescence, dr sean conley said.

Rest assured i expect the president to continue carrying out his duties without disruption while recovering, he added.

Mr trumps diagnosis injects a new level of uncertainty into an already turbulent presidential campaign. it was not immediately clear if mr trumps quarantine would be over by the date of the next presidential debate on october 15, and how his quarantine would affect his ability to campaign in the final 32 days of the race.

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Mrs trump tweeted: as too many americans have done this year, & i are quarantining at home after testing positive for covid-19. we are feeling good & have postponed all upcoming engagements.

The president disclosed earlier on thursday that he and mrs trump had been tested for the virus after hope hicks, one of his closest aides, tested positive just two days after the president shared the debate stage with democratic rival joe biden in cleveland, ohio.

Mr bidens campaign did not release any immediate statements about the presidents diagnosis or about whether the former vice-president would also be tested.

Ms hicks had been among the aides who travelled with mr trump to the event, as were all of the presidents adult children, some of whom were pictured not wearing masks. ms hicks also accompanied mr trump to a campaign rally in minnesota the following day, but was quarantined on the air force one flight home after showing symptoms for the virus, us media reported.

In a television interview with fox news host sean hannity earlier on thursday, mr trump appeared to suggest that ms hicks had contracted the virus through her interactions with soldiers and law enforcement officers who would come over to her.

It is very, very hard when you are with people from the military or from law enforcement and they come over to you and they want to hug you and they want to kiss you...you get close and things happen, mr trump said.

His diagnosis represents a historic moment in the us presidency. while most people who contract coronavirus recover from the illness, the virus has been most detrimental to americans aged 65 and over. mr trump is 74. mr biden is 77.

Sam vinograd, a former national security adviser to president barack obama, tweeted, ahead of mr trump's positive diagnosis, that the confirmation of ms hicks' illness was a code red momentfor the us government, noting how many white house and administration staffers work in close physical proximity to each other.

A pandemic in the [west wing] is a worst-case scenario. immediately, critical resources will be diverted to mitigate any outbreak at the most senior levels of government.

The presidents positive diagnosis comes amid a bitter campaign for re-election with mr trump trailing mr biden both in national polls and key battleground states.

Amid the falling poll numbers, mr trump had ramped up his public events schedule. he was holding multiple mass rallies a week a style of campaigning that propelled him to the white house four years ago despite criticism from public health experts who warn that such events can help spread the disease, especially when many in the audience do not wear masks.

At tuesdays debate, mr trump pushed back against the suggestion that the rallies were dangerous.

Weve had no negative effect, and weve had, 35 to 40,000 people at some of these rallies, mr trump asserted. however, after an indoor trump rally in tulsa, oklahoma this summer, herman cain, a former candidate for the republican presidential nomination, contracted coronavirus and died.

Mr trump has also downplayed the effectiveness of masks despite contrary advice from us public health experts and suggested that wearing them made some people, such as waiters, more likely to transfer the disease.

The president has also mocked mr biden for wearing one.

Every time you see him, hes got a mask, mr trump said. he could be speaking 200 feet away from them and he shows up with the biggest mask ive ever seen, mr trump said.

The us has confirmed 7.2m cases and more than 200,000 deaths since the start of the pandemic, according to data from johns hopkins university, more than any other country.

Mr trump had been scheduled to host a rally in florida on friday night followed by two rallies in wisconsin on saturday. the white house published a revised schedule for the president on friday morning cancelling all public events.

With additional reporting by peter wells in new york and hudson lockett in hong kong