The White House has said staff is regularly tested for the virus, and O'Brien is the most senior official to be found positive amid the pandemic.
US President Donald Trump's national security adviser Robert O'Brien has tested positive for the novel coronavirus, but there is no risk of exposure to Trump or Vice President Mike Pence, the White House said in a statement.
"He 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," according to the statement.
The White House has said staff is regularly tested for the virus, and O'Brien is the most senior official to be found positive amid the pandemic.
A US military member who works at the White House as a valet tested positive for coronavirus in May as did Vice President Mike Pence's press secretary.
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