Black death the most devastating natural disaster in european history in the mid fourteenth century. Ravaging europe and causing economic, social, political, and cultural upheaval. Bubonic plague, the most common and most important form of the black death, was spread by black rats infested with fleas who were host to the deadly bacterium yersinia pestis. Death was the first major epidemic disease to strike europe since the 7th century, an absence that helps explain medieval europe"s remarkable population growth. Europe in october 1347, when genoese merchants brought it from caffa to the island od sicily off the coast of southern italy. Mortality figures for the black death were incredibly high. The european population declined by 25-50 percent between 1347: the black death had spread to northern europe by the end of 1348. Jacquerie peasant revolt broke out in 1358 in northern france. Hundred years war began in a burst of knightly enthusiasm.