The Guardian reports that in a video posted on Twitter, Johnson, confirmed he had developed mild symptoms -- 'a temperature and persistent cough' -- over the last 24 hours and, on the advice of the chief medical officer, he took a test which returned positive for coronavirus.Johnson said he was now self-isolating and working from home. He said thanks to "the wizardry of modern technology' he would continue to lead the national fightback against the virus.