Anyone listening to the BBC this week could be forgiven for thinking that the musician Bob Geldof had just emerged from Africa, like a latter-day Dr Livingstone, the first westerner with news of a deadly new virus. He and his makeshift band of celebrities have adopted Ebola, their song blazing from the radio while Geldof himself has been in every studio exhorting people, with his usual stream of expletives, to buy it.