The Black Death kills a third of Europe's population
Plague carried from a Crimean siege reaches Sicily and spreads along every trade route in Europe
Quick facts
- Pathogen
- Yersinia pestis
- Entry point
- Sicily, via Genoese ships from Caffa
- Estimated deaths
- 25-30 million in Europe
- Population recovery
- Not until c. 1550
What happened
The plague bacterium Yersinia pestis reached Europe in 1347 when Genoese ships fleeing a Mongol siege of the Black Sea port of Caffa carried infected rats and fleas to Sicily; besieging Mongol forces at Caffa had reportedly catapulted plague-infected corpses into the city, spreading the disease to the Italian traders there. From Sicily it spread along Mediterranean and overland trade routes, reaching France, Spain, Britain, and Ireland by the end of 1349 and Germany, Scandinavia, and Russia through 1350-1352. Medieval doctors, unaware of bacteria, had no effective treatment and often made things worse by ignoring quarantine, since panicked residents fleeing outbreaks frequently carried the disease with them. Mortality varied enormously by city, from Florence's loss of 50,000 of its 85,000 residents to Milan's comparatively light toll, but historians estimate 25 to 30 million deaths across Europe, on average 30 percent and in the worst-hit areas up to half the population of affected regions.
Why it matters
Europe's population did not return to its pre-1347 level until around 1550, and the sudden, catastrophic shortage of labor gave surviving peasants unprecedented bargaining power, accelerating the decline of serfdom, driving demands to end labor wage caps, and feeding a broader questioning of authority that fed directly into revolts like England's Peasants' Revolt a generation later.
How we know
Genetic studies of plague DNA recovered from medieval burial sites, published in 2011, traced the pathogen's origin to central Asia, corroborating contemporary chronicle accounts of the disease's spread from the Black Sea into the Mediterranean.
Sources
- World History Encyclopedia. Black Death · Reputable sourceworldhistory.org · The domain "worldhistory.org" is on our Reputable source registry. · Link is live and its text matches the event's key terms (Jul 2026)
- World History Encyclopedia. Black Death · Reputable sourceworldhistory.org · The domain "worldhistory.org" is on our Reputable source registry. · Link is live and its text matches the event's key terms (Jul 2026)
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