In a public advisory, written back in the summer, Dr Vivek Murthy warned of a growing ‘epidemic of loneliness and isolation’, which he believes is not just destined to affect the physical and mental health of individuals but could end up being detrimental to democracy itself. ‘The nation’s doctor’ speaks to Jonathan Freedland about why some bad faith actors are choosing to manipulate this problem and how political leaders on all sides can address it before it gets worse