It killed up to half of Europe's population in four years — and the survivors inherited a radically different world: higher wages, less serfdom, and the seeds of the Renaissance.
The Black Death arrived in Europe in October 1347, carried by fleas on rats aboard twelve Genoese merchant ships docking in Sicily. By the time port authorities ordered the ships back out to sea, it was already too late. Over the next four years, the plague swept across the continent from Sicily to Norway, killing an estimated 25 to 50 million people — somewhere between 30% and 60% of Europe's entire population.
The disease came in three forms, all caused by the bacterium Yersinia pestis. Bubonic plague caused grotesque swellings in the groin, armpits, and neck — buboes that oozed pus and bled — followed by fever, vomiting of blood, and death within two to seven days in 80% of untreated cases. Pneumonic plague attacked the lungs and was almost always fatal. Septicemic plague, where the bacteria entered the bloodstream directly, killed so fast that victims sometimes died before the buboes even had time to develop.
The death toll in individual cities was staggering. Florence lost 80% of its population in four months in 1348. Half of Paris — roughly 50,000 people — died. In some English parishes, entire communities were wiped out. The scale of mortality overwhelmed burial traditions: mass graves were dug containing hundreds and sometimes thousands of bodies, priests could not keep up with last rites, and the living began to run out of ways to mourn the dead.
Medieval Europeans had no understanding of germ theory and no defense against what they were facing. Physicians attributed the plague to 'bad air' (miasma) or a conjunction of planets. Common treatments included lancing the buboes, applying live chickens to the swellings, and burning aromatic herbs. Some doctors wore early protective gear — long robes, gloves, and the famous beak-shaped masks filled with herbs — but mostly to filter the imagined bad air rather than actual contagion.
The search for someone to blame turned lethal. Jews were accused of poisoning wells across Germany, France, and Spain, and thousands were massacred in pogroms despite Pope Clement VI issuing a papal bull explicitly stating they were not responsible. In some cities, the Jewish population was entirely exterminated before the plague itself even arrived — one of many atrocities committed in the panic.
The long-term social consequences were enormous and paradoxical. The surviving peasants — suddenly scarce — found themselves with bargaining power they had never possessed. Wages rose dramatically across Europe. Serfs demanded freedom in exchange for their labor. The feudal system that had kept the poor in bondage for centuries began to crack. Peasant revolts broke out across England, France, and the Low Countries.
Historians now debate whether the Black Death was ultimately a catalyst for European modernity. The massive death toll disrupted the Church's authority (why had God allowed this?), accelerated the decline of feudalism, triggered an enormous demand for labor-saving technology, and — combined with the flight of Greek scholars from Constantinople — helped spark the Renaissance. The catastrophe that killed half a continent may have helped birth the modern world.