US President Donald Trump has said he and the US first lady are in quarantine after one of his closest aides tested positive for coronavirus.
He tweeted that both he and Melania Trump were now awaiting their own test results after Hope Hicks was infected.
The 31-year-old adviser to the president is the closest aide to Trump to test positive so far.
She travelled with him on Air Force One to a TV debate in Ohio earlier this week.
Hicks was pictured getting off the presidential jet on Tuesday in Cleveland without a mask.
She was in even closer proximity to him aboard the presidential helicopter Marine One on Wednesday when the president held a rally in Minnesota.
Trump tweeted on Thursday night: "Hope Hicks, who has been working so hard without even taking a small break, has just tested positive for Covid 19. Terrible!
"The First Lady and I are waiting for our test results. In the meantime, we will begin our quarantine process!"
It is not clear how the quarantine will affect arrangements for the second presidential debate, which is scheduled for 15 October in Miami, Florida.
During a phone call with Fox News host Sean Hannity on Thursday night, Trump said he and Trump "spend a lot of time with Hope".
"So we'll see what happens," said the president, adding that Hicks often wore masks but still tested positive.
The disease has infected more than 7.2 million Americans, killing over 200,000 of them.
The White House tests aides and anyone else who comes into contact with the president daily.
Trump mostly spurns mask-wearing and is often pictured not socially distanced with aides or others during official engagements.
According to Bloomberg News, Hicks is experiencing symptoms of the disease, and was quarantined on Air Force One on the trip back from Minnesota.
Hope Hicks, who has been working so hard without even taking a small break, has just tested positive for Covid 19. Terrible! The First Lady and I are waiting for our test results. In the meantime, we will begin our quarantine process!— Donald J. Trump (@realDonaldTrump) October 2, 2020
Hicks is the latest White House aide to contract Covid-19. Vice-President Mike Pence's press secretary Katie Miller tested positive in May and recovered.
That same month, a member of the US Navy who was serving as one of Trump's personal valets tested positive for coronavirus.
But the White House said neither the president nor vice-president were affected.
National Security Adviser Robert O'Brien, a number of Secret Service agents, a Marine One pilot and a White House cafeteria worker have also tested positive.
Hicks was a campaign spokeswoman during Trump's candidacy before becoming communications director in his White House.
She stepped down in March 2018 to become chief communications officer at Rupert Murdoch's Fox, before returning to the White House in February.