What was the “Black Death” (1347–1351) primarily?

The story behind the answer

Caused by the bacterium Yersinia pestis, it spread via flea-infested rodents and, in its pneumonic form, through respiratory droplets. Between 1347 and 1351 it swept across Eurasia and North Africa, killing perhaps a third to half of Europe’s population—far exceeding the toll of wars, famines, or market shocks of the era.

Trade routes carried it from Central Asia to Black Sea ports like Caffa, then on Genoese ships into the Mediterranean. The catastrophe reshaped society: severe labor shortages raised wages and mobility, weakening parts of feudalism; authorities tried new public-health measures, including 40-day isolation (“quarantine”) in places like Ragusa; and fear fueled religious movements and persecution, especially of Jews. Its mark endures in art, literature, and the very vocabulary of disease control.