"And no bells, tolled, and nobody wept no matter what his loss because everyone expected death.... And people said and believed, "This is the end of the world." (Agnolo di Tura, citizen of Siena, 1348)

The Black Death first struck mainland Italy in January, 1348, at the cities of Genoa and Venice. From there the disease spread to port after port, following the trade routes, journeying inland with the rats that shuffled and tunneled in the thatch of the peasants roofs and the lice they carried, as well as with infected persons. A few villages were left mysteriously untouched, but most were scathed by the illness. Some lucky individuals recovered while others, rising healthy in the morning, would by nightfall die an agonizing death.

In vain the physicians bled their patients, and in vain the healthy tried to remove themselves from the foul airs that were said to cause death. In vain, families fled to areas where disease was absent -- too often only to carry the plague along with them as a cruel if unintended gift. The living dropped dead in the streets. The shallow soil covering rapidly-filling common graves could not prevent dogs from digging up the bodies to gnaw upon them. The residents of Milan tried to save themselves by walling in the ill, along with their families, and leaving them to perish. Elsewhere Christians willingly submitted to bloody beatings, seeking to propitiate God's wrath. Jews became scapegoats and were tortured along with lepers and misfits. All to no avail. Within three years, the plague had swept from the Mediterranean through Scandinavia, and a third of the population of Europe had died.

Today scholars have a deeper understanding of the bubonic plague that ripped apart Europe's settlements, economy, and social fabric in the mid-1300s. The plague bacillus -- Pasteurella pestis -- traveled by caravan from China to the Crimea, and from there by ship to a Europe whose vulnerability had soared to the breaking point. After a few centuries of massive economic growth, nearly all of northwestern Europe had become densely populated, to the point that food was scarce, the environment degraded, and deforestation had left many areas short of wood for fuel or building materials. Many districts by 1350 were struggling to feed themselves; their population had reached a size that would not be matched again until the beginning of the 20th century. Mechanisms for the rapid spread of disease were in place: more intensive trade routes were shipping goods (and infectious agents) more quickly and year-round. Black rats, ready vectors for the bacillus, had spread throughout Europe.

And then the climate changed. The onset of the Little Ice Age brought colder and wetter weather. Grain crops failed. Already-undernourished people became hungrier, their immune systems correspondingly weaker. The overpopulated, underfed populations presented a ready fuel. The changing climate was the tinder, the plague bacillus the spark. They came together to torch Europe until the continent lay blanketed in death.