What city did black plague sweep through killing thousands when did thisoccur and why?

The Black Plague swept through Europe in the mid-14th century, with one of the most affected cities being Florence, Italy, in 1348. The outbreak, caused by the bacterium Yersinia pestis, killed an estimated one-third of the population. The disease spread rapidly due to increased trade, urban crowding, and poor sanitation, exacerbated by the movement of rats and fleas. The devastating impact of the plague led to significant social, economic, and cultural changes across Europe.