The Bubonic Plague, also known as the Black Death, was a devastating pandemic that afflicted Europe and Asia in the 14th century. It was caused by the bacterium Yersinia pestis, which is usually transmitted between animals by fleas and can be passed to humans. The plague resulted in the deaths of an estimated 30-60% of Europe's population between 1347-1351 and was one of the deadliest pandemics in human history.