History of the Black Death | How One Bacteria Killed 200 Million People

In the fourteenth century, a single bacterium emerged from the grasslands of Central Asia and went on to kill an estimated two hundred million people worldwide — roughly a third to half of Europe's entire population. This is the full story of the Black Death, told from its origins on the Eurasian steppe to its final retreat back into the lands it came from. We trace how the Pax Mongolica and the Silk Road first gave the plague bacterium, Yersinia pestis, a path out of its natural rodent reservoir. We follow it to the siege of the Crimean trading city of Caffa, where a conflict between Genoese merchants and the Mongol khan Jani Beg turned into one of history's earliest documented uses of biological warfare. From there, we track the disease as it crossed the Mediterranean by ship, devastating Constantinople, Sicily, Genoa, and Marseille, before reaching Florence, Paris, and eventually England and Scandinavia. Along the way, we examine the science of the three plague variants — bubonic, pneumonic, and septicemic — and how medieval society responded with everything from astrology and bloodletting to the strict quarantine measures pioneered in Venice, which gave us the very word "quarantine." We also confront the darkest chapter of this history: the persecution of Jewish communities who were falsely blamed for the disease. Sources referenced in research: • John Kelly, The Great Mortality (HarperCollins, 2005) • Ole J. Benedictow, The Black Death 1346-1353: The Complete History (Boydell Press, 2004) • World Health Organization, plague fact sheets • Centers for Disease Control and Prevention, plague history and biology resources • Giovanni Boccaccio, The Decameron, introduction (primary source account of Florence) • Cambridge University Press, journal articles on medieval demography • Encyclopaedia Britannica, entries on the Black Death and Mongol Empire • National Archives (UK), records on the Black Death in England