The Black Death

The Black Death was the second great pandemic of plague, caused by the bacterium Yersinia pestis and spread primarily by fleas carried on black rats, that struck Europe, the Middle East and parts of North Africa between 1347 and 1351, after arriving in Sicily aboard Genoese trading ships fleeing a Mongol siege of the Crimean port of Kaffa. Modern estimates of its mortality vary widely, commonly ranging from roughly a third to as much as sixty percent of Europe's population within a few years, with even wider estimates for individual regions, and no possibility of a precise figure given the absence of reliable contemporary records. It killed an enormous share of the population of every region it reached, causing labor shortages that historians credit with weakening the manorial system of serfdom in western Europe, triggering religious and social upheaval including the flagellant movement and violent persecution of Jewish communities blamed for the disease, and prompting the earliest known public health measures, including the quarantine period from which the word itself derives, first instituted at the port of Ragusa, present-day Dubrovnik, in 1377. Plague did not disappear after 1351 but recurred in periodic waves across Europe for the next four centuries, including the Great Plague of London in 1665, though none matched the mortality of the first outbreak. The pandemic belongs to a larger wave of plague, the Second Pandemic, whose origins historians and geneticists increasingly trace to Central Asia in the early fourteenth century, connected to the same overland trade routes that the Mongol Empire's unification of Eurasia had opened.