A sweeping global history that looks beyond European urban centers to show how slavery, colonialism, and war propelled the development of modern medicine. Most stories of medical progress come with ready-made heroes. John Snow traced the origins of London's 1854 cholera outbreak to a water pump, leading to the birth of epidemiology. Florence Nightingale's contributions to the care of soldiers in the Crimean War revolutionized medical hygiene, transforming hospitals from crucibles of infection to sanctuaries of recuperation. Yet histories of individual innovators ignore many key sources of medical knowledge, especially when it comes to the science of infectious disease. Reexamining the foundations of modern medicine, Jim Downs shows that the study of infectious disease depended crucially on the unrecognized contributions of nonconsenting subjects-conscripted soldiers, enslaved people, and subjects of empire. Plantations, slave ships, and battlefields were the...