The US vice president's spokesperson became the second White House staffer this week to test positive for the coronavirus, officials said Friday.

News that staffer Katie Miller had fallen ill boosted fears that the White House is at risk of becoming a viral hot spot just when Trump is leading efforts to wind down nationwide quarantine measures that have devastated the world's biggest economy.

Miller is spokesperson for Vice President Mike Pence, giving her frequent access to high-level meetings. She is also married to top Trump aide Stephen Miller, the speech writer behind the administration's hardline immigration measures.

A senior administration official initially said only that a member of Pence's staff had been tested and found to have the coronavirus.

Trump, speaking later at an event with Republican lawmakers, identified the person as "Katie," saying she works with Pence as a "press person." This confirmed multiple US media reports that Katie Miller was the person in question.

Well wishes

On Friday, Miller thanked people for their well wishes, and in a tweet said: "I'm doing well and look forward to getting back to work for the American people."

As recently as Thursday, Miller was seen mingling with officials at an outdoor prayer ceremony hosted by Trump and attended by dozens of people, including the wives of Trump and Pence and many senior staff.

Miller's positive test disrupted a trip by Pence to Des Moines, Iowa, with six people who may have had contact with her made to get off the airplane.

"Out of abundance of caution we went back and looked into all the person's contacts most recently," said the senior administration official, who asked not to be named.

On Thursday, a Trump spokesperson said the president's valet, a member of the military who is in close contact with the president, had tested positive.

Trump and Pence were tested and confirmed to be negative. Both are tested daily