EMPIRES ARE BIG AND MICROBES SMALL, but both have shaped history by conquering territories and bodies, leaving death, disease, and devastation in their wake. Yet humans have survived many such onslaughts and brought, at hard-won cost, peace, knowledge, and protection.
Conquerors such as the Romans in Britain or the Mongols in China first massacred local people who were not yet “immune”—that is to say, submissive. Huge numbers of people died, but afterward rulers and subjects worked out an accommodation where regular taxation replaced mere plunder. In the same fashion, diseases settled into an arrangement with humanity. The initial casualties as new viruses and bacteria emerged from the wilderness died down as immunity developed or diseases became less lethal, allowing a mutual, if uneasy, existence.
Disease and empire also marched together.…