The Great Mortality: An Intimate History of the Black Death, the Most Devastating Plague of All Time

by John Kelly

The Plague of Justinian marked an important turning point in Europe’s relationship with infectious disease. The centuries preceding the First Pandemic were a period of chronic, devastating epidemics. In the second and third centuries, smallpox and measles outbreaks may have killed a quarter to a third of the population in parts of the Roman Empire. The centuries after Justinian were, if not disease-free, then close to it. During the early Middle Ages, all forms of infectious illness became uncommon and plague (as far as is known), nonexistent. For this disease-free interim, the collapse of civilization deserves some credit. A disease is more than just a pathogen plus a transportation system. To ignite an epidemic, a friendly environment is also necessary, and after Rome fell, the environment in Europe, particularly northwest Europe, became increasingly unfriendly to epidemic disease. In the early Middle Ages, the population plunged precipitously, shrinking the pool of potential host-victims. In the second and third centuries, Roman Europe had 50 to 70 million people; by 700, Europe had 25 to 26 million. The disappearance of urban life removed two other necessities: concentrations of people, and filthy, rodent-infested streets. At its height, the city of Rome had a population variously estimated at half a million to ten million; by 800, no city in Europe contained more than twenty thousand residents. “In the middle of the debris of great cities,” wrote one Dark Ages scribe,...