US national security adviser, Robert O'Brien, has become the highest ranking official in President Donald Trump's inner circle to test positive for the coronavirus.
Announcing the infection, the White House said in a statement there was no risk of exposure to Mr Trump or Vice President Mike Pence.
The announcement caught some White House staff off guard, as there had not been an internal memo about it, one source said.
White House officials do not reliably wear masks while working in the West Wing because of the regular testing regimen.
An administration official said Mr O'Brien had not had contact with the president in several days.
The National Security Council did not immediately respond to questions about Mr O'Brien.
The White House statement said: "He (O'Brien) has mild symptoms and has been self-isolating and working from a secure location off site. There is no risk of exposure to the president or the vice president. The work of the National Security Council continues uninterrupted."
Mr O'Brien, who took over as national security adviser from John Bolton last September, had travelled to Paris in mid-July to represent the United States at Bastille Day ceremonies.
He met French President Emmanuel Macron while there.
The virus has been disruptive for Mr Trump, who last week was forced to cancel plans for the Republican convention in Jacksonville, Florida, where he was to be formally nominated for a second term.
A US military member who works at the White House as a valet tested positive for coronavirus in May as did Mr Pence's press secretary.
