But most of humanity—not just medieval people—lacked the ability to fight infections or even under-stand how they spread for much of history. England during the Renaissance suffered regular deadly outbreaks of plague, smallpox, syphilis, typhus, malaria, and a mysterious illness called “sweating sickness.” Upon contact with Europeans, upwards of 95 per cent of the Indigenous peoples of the Americas were killed by European diseases. Plagues even rav-aged the twentieth century: from 1918–1920, half a billion 14 / The Devil’s Historianspeople were infected with the Spanish Flu global pandemic, which killed between 50 and 100 million people. And let’s not forget that we are currently living with the global pandemic of HIV/AIDS