The US commander-in-chief has Covid-19 and the top military brass are now isolating as the coronavirus pandemic takes a toll on the national security establishment of the most powerful nation in the world. As the coronavirus breached the walls of the Pentagon, the Defence Department was quick to stress that there had been "no change to the operational readiness or mission capability of the US Armed Forces". President Donald Trump, the custodian of the nuclear codes, tested positive for the coronavirus last week and was in hospital for three days, returning to the White House on Monday. No sooner had Mr Trump returned to work than the Pentagon announced that members of the Joint Chiefs of Staff, including Gen Mark Milley, the chairman, were self-quarantining. They all tested negative for Covid-19 but would isolate after coming into contact during meetings last week with the vice commandant of the Coast Guard, Adm Charles Ray, who tested positive for the coronavirus. It is not clear when Adm Ray was infected, although he attended a number of White House events including the September 27 announcement by Mr Trump of Amy Coney Barrett as his nominee for Supreme Court. At least 11 others who attended the event have now tested positive but the White House has not done any contact tracing. The Coast Guard said Adm Ray had tested positive on Monday after showing mild symptoms and was quarantined at home. The list of those who attended meetings with Adm Ray read like a Who's Who of the US military's top brass. Besides Gen Milley, they included Gen John Hyten, the Joint Chiefs vice chairman, Adm Michael Gilday, chief of naval operations, Gen James McConville, the army chief of staff, and Gen Charles Brown, the air force chief of staff, a Pentagon official said. Also attending meetings with Adm Ray were Gen Daniel Hokanson, the head of the National Guard, Gen John Raymond, chief of the Space Force, and Gen Paul Nakasone, the director of the National Security Agency and head of US Cyber Command, the official said. "All have been tested with no positive results to report and none are exhibiting any symptoms," the official said. Pentagon spokesman Jonathan Hoffman said those who had come into contact with Adm Ray would self-quarantine "out of an abundance of caution." "We are conducting additional contact tracing and taking appropriate precautions to protect the force and the mission," Mr Hoffman said. "Senior military leaders are able to remain fully mission capable and perform their duties from an alternative work location." Defence Secretary Mark Esper was on a foreign trip last week and was not among the Pentagon officials who are going into isolation. Mr Esper attended in a conference on the future of the US Navy on Tuesday but did not make any comments about the quarantine situation at the Pentagon. Senior officials said the US threat level had not been heightened last week following the announcement that the president had Covid-19 and no new threats had been detected. But former US officials said the administration needed to remain wary. "We have to look at whether or not any of our global adversaries want to take advantage of the distraction taking place right now," John Brennan, who served as CIA director under president Barack Obama, told NPR radio. Stephen Hadley, who served as national security adviser to former president George W Bush, also warned that "adversaries may think that America may be distracted, so that they can get away with something". Representative Adam Smith, chairman of the Democratic-majority House Armed Services Committee, hit out at Mr Trump's handling of the coronavirus crisis and said it had endangered national security. "While our military can still operate while leadership is quarantined, the national security implications of the president's recklessness cannot be overstated," Mr Smith said. "Our adversaries are always looking for any weakness to exploit. "President Trump's pathetic attempts to exude strength aren't fooling anyone – Americans know he is weak and so do those who wish us harm," Mr Smith said. "Instead of leading, President Trump continues to wilfully jeopardise the safety and security of the American people and our military apparatus."