In less than a year some malign necromancy has transformed the fearless social beings who once thronged shops and cafés in the run-up to each Christmas into an infestation of dangerous, outsized germs: or, if scrupulous examination of the facts has left you confident that “the novel coronavirus” is no more threatening to moderately healthy people than the nastier brands of flu, into the crazed adherents of some apocalyptic cult.