The Black Death was a devastating global epidemic of bubonic plague that struck Europe and Asia in the mid-1300s. It was caused by the bacteria Yersinia pestis, which was often transmitted via flea bites from infected rats. Symptoms included swollen and bleeding lymph nodes, as well as fever, vomiting and diarrhea. It ultimately killed an estimated 25-50 million people in Europe alone, reducing the population by around 50%. The plague spread along trade routes from Central Asia to Europe in 1347-1351, leaving massive societal impacts like pogroms against Jewish communities before subsiding by 1351.