The most important parts of the book are undoubtedly those that say something larger about human behaviour. It is striking that primates seem to quarantine newcomers, keeping them at the edge of a troop for some weeks. Striking too that a 2011 psychological study shows that people who had been recently vaccinated were less likely to show prejudice towards immigrants than those unprotected by a vaccine. Yet if we are to fight pandemics, Kenny argues, we have to fight instincts that “are increasingly ill-matched to a connected world”.
Medieval medicine had no answer to the Black Death. As Kenny points out, for most of history, 'medical advice was often worse than useless'. The only thing that worked was isolation. Lepers were herded into lazar-houses and left, literally, to rot. There was little sympathy for a disease thought to be caused by lechery and most likely to strike 'those . . . who look upon a woman lustfully'. In the past couple of centuries, we have developed three effective weapons in the battle against infectious disease.