President Donald Trump’s national security adviser, Robert O’Brien, has tested positive for the coronavirus — making him the highest-ranking official to test positive so far. The White House said O’Brien has mild symptoms and “has been self-isolating and working from a secure location off site.” Officials did not respond to questions about the last time the president and O’Brien had contact, but the White House insisted that “There is no risk of exposure to the President or the Vice President” and that the “work of the National Security Council continues uninterrupted.”