One outbreak, then four and a half centuries of return
The second plague pandemic began with the Black Death, which reached Europe in 1346 and killed an estimated 75 to 200 million people across Europe, Asia and the Middle East within about four years, before receding after 1353 but becoming endemic and recurring regularly for centuries. Later major outbreaks included the Great Plague of Seville from 1647 to 1652, the Great Plague of London in 1665 and 1666, and the Great Plague of Marseille from 1720 to 1722, with a final significant wave affecting Ottoman territories and Egypt lasting into 1813 and 1814, giving the pandemic an overall span of roughly four and a half centuries rather than a single contained episode.
From chronicle description to confirmed DNA evidence
Historians reconstruct the pandemic’s course through several kinds of evidence: parish registers and tax records documenting mortality patterns, contemporary literary accounts such as Giovanni Boccaccio’s Decameron describing conditions in Florence, and letters from figures including Petrarch recording the psychological toll on survivors. A significant recent addition is genetic evidence: a 2010 study provided confirmation, through DNA analysis of remains from mass graves, that Yersinia pestis caused the pandemic, resolving a question that documentary sources alone, describing symptoms rather than pathogens, could not settle. Later research recovering plague DNA from teeth in Kyrgyzstan has further reshaped understanding of where the pandemic began.
Genoese traders, Crimean ports, and a disease already travelling
The disease is understood to have spread from parasitic fleas carried by rodents into human populations, reaching Europe through Genoese merchants trading via the Crimean port of Kaffa in 1347, after which it moved rapidly along Mediterranean and European trade routes. Research by the demographic historian Jean-Noel Biraben established that plague was present somewhere in Europe in every year between 1346 and 1671, indicating a level of persistence and recurrence that meant no single generation across that span was entirely free of active outbreaks, a continuity that shaped medical, religious and economic responses across successive centuries rather than a single crisis followed by full recovery.
Where it began and how it spread, both still argued over
Two specific points remain unresolved among specialists. The pandemic’s geographic origin was long assumed to lie in Mongolia, but twenty-first century research instead points toward the northwestern shores of the Caspian Sea, or further into Central Asia near modern Kyrgyzstan, with some scholars now doubting the plague reached India and China as early or as severely as once believed. A separate dispute concerns transmission: whether infected fleas travelling on rats drove the spread, as long assumed, or whether human fleas and body lice, or direct person-to-person transmission, played the larger role, a question archaeologists have raised partly because evidence for a mass die-off of rats in some affected cities, including London, is thinner than the traditional account would predict.
A death toll that reshaped labour, land and law across Europe
The initial Black Death alone is estimated to have killed between a quarter and three-fifths of Europe’s population depending on the region, with specific tolls including 700,000 to 800,000 deaths in England in the early 1360s and roughly half of Paris’s population of about 100,000. Later individual outbreaks remained severe in their own right, with France recording around a million deaths between 1628 and 1631 and Naples close to 1.25 million between 1656 and 1658, figures that meant plague continued to reshape populations, labour markets and land tenure patterns across Europe for centuries after the initial fourteenth-century wave had passed.
Worth reading for the evidence itself, not just the toll
The pandemic is worth studying closely because so much of what is now confirmed about it, the specific bacterium responsible, its likely Central Asian rather than Mongolian point of origin, depends on evidence that simply did not exist for most of the centuries historians have been trying to understand it, namely genetic analysis of centuries-old remains. Readers who know the outline, a fourteenth-century catastrophe that killed a large share of Europe, gain the most from tracing how recently some of the most basic facts about causation and origin were actually confirmed, and how much about its eventual disappearance in the early nineteenth century still resists a fully settled explanation.