Abstract

Over millennia, epidemics have wielded as much sway over human affairs as have wars, economic crises, and political upheavals. Devastating epidemics in the past have changed the course of history. This article focuses on the yellow fever epidemic of 1802 in St. Domingue to demonstrate how science has deepened our understanding of the epidemic, and hence of the Haitian Revolution. Genetics, affirming epidemiology, demonstrated that the origin of the virus was in Africa, and genomics demonstrated that the vector of yellow fever, the _Aedes aegypti_ mosquito, evolved in the context of the ecological creation of the Sahara and the Sahel. The vector fed on humans and reproduced in man-made water containers, allowing transport to the Caribbean during the African slave trade. Serological studies in Africa later demonstrated that many African-origin slaves would have had adaptive immunity. French fighters did not, and they were decimated. The French withdrew, Haiti was created, and the Louisiana Purchase was executed.