WASHINGTON (BLOOMBERG) - United States President Donald Trump said that he would begin self-quarantine while waiting for coronavirus test results after Ms Hope Hicks, one of his closest aides, tested positive for Covid-19.

"She did test positive. I just heard about this," Mr Trump said in an interview on Thursday (Oct 1) night on Fox News, about two hours after Bloomberg News first reported Ms Hicks' positive test.

Later, in a tweet, the President said that he and First Lady Melania Trump had been tested for the virus and were waiting on the results.

"In the meantime, we will begin our quarantine process!"

It was unclear from the President's tweet whether that meant he planned to halt campaigning for re-election. An official White House schedule released less than an hour earlier still listed his plans to meet supporters in Washington on Friday, then fly to Florida for a campaign rally near Orlando.

Ms Hicks travelled with Mr Trump aboard Air Force One to and from the presidential debate in Cleveland on Tuesday and to a Minnesota rally on Wednesday. She felt poorly in Minnesota and quarantined aboard the presidential plane on the way home, according to people familiar with the matter.

The people asked not to be identified because her infection had not been publicly announced until Mr Trump's interview. Messages left for Ms Hicks were not immediately returned.

"I'll get my test back either tonight or tomorrow morning," Mr Trump said. He said he "was surprised" about Ms Hicks' infection, remarking that she often wears a mask. "She is a very warm person," he said.

He suggested that members of the military or law enforcement might pose a risk of infection to White House staff, including himself.

"You know, it's very hard when you're with soldiers, when you're with airmen, you're with Marines and police officers - I'm with them so much - that when they come over to you, it's very hard to say, 'stay back, stay back', you know," Mr Trump said.

"It's a tough kind of a situation. It's a terrible thing," he said.

He added later in the interview that "people from the military or from law enforcement" approach him and his staff and "want to hug you and they want to kiss you because we really have done a good job for them".

"You get close and things happen," he said.

Ms Hicks is the latest person in Mr Trump's orbit to contract the virus, which has infected more than 7.2 million Americans and killed more than 200,000. Other senior staff have contracted Covid-19 and recovered, including National Security Adviser Robert O'Brien, but few spend as much time with the President as Ms Hicks, whose service dates to his 2016 campaign.

Some people close to Ms Hicks were told that she is experiencing symptoms of the disease.

"The President takes the health and safety of himself and everyone who works in support of him and the American people very seriously," White House spokesman Judd Deere said in a statement.

"White House Operations collaborates with the physician to the President and the White House Military Office to ensure all plans and procedures incorporate current CDC guidance and best practices for limiting Covid-19 exposure to the greatest extent possible, both on complex and when the President is travelling."

The development is likely to inflame criticism of the Trump administration's response to the coronavirus pandemic, as well as the president's disregard for public health measures to combat it.

Mr Trump seldom wears a mask and has belittled his re-election challenger, Mr Joe Biden, for routinely covering his face. The President has resumed holding large campaign rallies at which thousands of his supporters gather, shoulder to shoulder, few in masks.

Most of the events are held outdoors at airports but two recent events in Arizona and Nevada were indoors, a setting that public health experts warn raises the risk of virus transmission.

Ms Hicks travelled with Mr Trump to the debate with Mr Biden on Tuesday and to a Minnesota rally on Wednesday. Mr Trump's entourage entered the debate hall without face coverings, or removed them as they sat down, and refused an offer of masks from a doctor at the Cleveland Clinic, which was co-hosting the event.

Mr Biden's guests wore masks.

Ms Hicks was seen on Tuesday riding maskless in a staff van with White House senior adviser Stephen Miller, campaign adviser Jason Miller and others.

When they returned to Washington on Tuesday, Mr Stephen Miller and Ms Hicks were seen sharing an umbrella as they exited Air Force One in the rain. Mr Miller's wife, Katie Miller - Vice-President Mike Pence's press secretary - recovered from Covid-19 earlier this year.

Ms Hicks felt poorly in Minnesota on Wednesday and was quarantined aboard Air Force One during the return flight, according to people familiar with the matter. She tested positive for the virus on Thursday.

Mr Trump is tested regularly, though it is not clear precisely how often. People who work in the White House are tested daily, including members of the press corps, and anyone scheduled to meet the President is tested beforehand.

Mr Trump's staff wear masks when travelling with him aboard the presidential helicopter, Marine One, and Ms Hicks observed that protocol this week.

But his aides worry that Mr Trump's lack of sleep during the final stretch of the presidential campaign could leave him especially vulnerable to infection. The President did not return to the White House until after midnight following his Tuesday and Wednesday trips.

Mr Trump's age, 74, also puts him at greater risk for serious illness from the virus.

A person familiar with the debate commission's testing protocols said there should have been no co-mingling between the Trump and Biden campaign staff in Cleveland, and that there were separate entrances and rooms for both groups.

The person added that everyone in the debate hall had to be tested 72 hours before the event, and everyone travelling with Mr Biden and top people in his campaign had to be certified by medical personnel that they had tested negative for the virus.