The Black Plague originated in Asia, likely China or the Gobi Desert, and was first recorded in Constantinople in 570 CE. It was caused by the bacterium Yersinia pestis and spread by fleas on rats. Symptoms included painful swellings, fever, vomiting, and death within 2-4 days. It spread along trade routes to Italy in 1347 and killed 30-60% of Europe's population by 1351, reducing the world population from 450 to 350 million. Lacking medical knowledge, Europeans scapegoated Jews, witches and lepers and engaged in flagellation to appeal to God. The plague had severe economic impacts including depressed trade and a labor shortage.