In 1854 a London doctor persuaded local officials to take the handle off a water pump on Broad Street, and a cholera outbreak that had killed hundreds faded away. In 1977 a hospital cook in Somalia named Ali Maow Maalin recovered from the last natural case of smallpox, a disease that had killed an estimated 300 million people in the twentieth century alone. In 1964 the US Surgeon General told Americans plainly what tobacco companies had worked to obscure: cigarettes cause lung cancer. None of these victories came from a single cure. They came from public health, the work of keeping whole populations from getting sick in the first place.

In this course you will learn what public health is and why its successes are so often invisible. You will follow John Snow as he founded epidemiology, see how sewers and clean water lengthened lives more than almost any medicine, and learn how vaccines and herd immunity work. You will study the shift to chronic disease and the long fight against tobacco, explore why health follows the ladder of wealth and status, and trace pandemics from the Black Death to COVID-19. The course ends with the question that underlies all the rest: how health institutions earn, lose and rebuild the public's trust.