33. The Recurring Plague
By 1352, the worst of the Black Death was over, and the pandemic had mostly burned itself out. Mostly, but not completely. Like a persistent ex turned crazy stalker, the Yersinia pestis bacterium kept coming back to wreak more havoc in subsequent decades. There were further outbreaks in 1361 to 1363, 1369 to 1371, 1374 to 1375, 1390, and 1400. None of the recurrences were as horrific as the original mid-century one, but they were still pretty bad: each time they hit, they killed about 10% to 20% of the population.
All in all, during the second half of the fourteenth century, the plague was introduced and reintroduced to Europe numerous times, arriving along the trade routes from China and Central Asia in multiple waves. Modern research suggests that climate fluctuations played a key role in those recurrences, as they affected populations of rats and other rodents infested with the plague-carrying fleas.