White House senior adviser Stephen Miller said he had tested positive for Covid-19 on Tuesday, the latest case of coronavirus reported among Donald Trump's inner circle since the Republican president announced he had the virus last week.
"Over the last 5 days I have been working remotely and self-isolating, testing negative every day through yesterday," Miller said in a statement.
"Today, I tested positive for Covid-19 and am in quarantine."
Trump returned to the White House on Monday after three nights in a military hospital, urging Americans not to be afraid and not to let the coronavirus dominate their lives.
The pandemic has killed more the 210,000 people in the United States, more than any other country.
White House Deputy Press Secretary Brian Morgenstern told CNN late on Tuesday that there were no new Covid cases in the White House beside Miller.
Trump said on Friday that he and first lady Melania Trump had tested positive for the coronavirus.
Others announcing they had tested positive in recent days include close Trump adviser Hope Hicks; White House spokeswoman Kayleigh McEnany; Trump's campaign manager Bill Stepien; and Republican Senators Mike Lee, Thom Tillis and Ron Johnson.
Miller's wife, Katie Miller, who is a spokeswoman for Vice President Mike Pence, tested positive for the virus in May.