How human institutions-markets, states, communities, religions, guilds and families-have helped both to control and to exacerbate epidemics throughout history.How do societies tackle epidemic disease? In Controlling Contagion, Sheilagh Ogilvie answers this question by exploring seven centuries of pandemics, from the Black Death to Covid-19. For most of history, infectious diseases have killed many more people than famine or war, and in 2019 they still caused one death in four. Today, we deal with epidemics more successfully than our ancestors managed plague, smallpox, cholera or influenza. But we use many of the same approaches. Long before scientific medicine, human societies coordinated and innovated in response to biological shocks-sometimes well, sometimes badly.Ogilvie uses historical epidemics to analyse how human societies deal with "externalities"-situations where my action creates costs or benefits for others beyond those that I myself incur. Social institutions-markets, states, communities, religions, guilds, and families-help us manage the negative externalities of contagion and the positive externalities of social distancing, sanitation, and immunization. Ogilvie shows how each institution enables us to coordinate, innovate and inspire each other to limit contagion. But each institution also has weaknesses that can make things worse. Markets shut down voluntarily during every epidemic in history-but they also brought people together, spreading contagion. States mandated quarantines, sanitation, and immunization-but they also waged war and censored information, exacerbating epidemics. Religions admonished us to avoid infecting our neighbours-but they also preached against science and medical innovations. What decided the outcome, Ogilvie argues, was a temperate state, an adaptable market, and a strong civil society where a diversity of institutions played to their own strengths and checked each other's flaws.