There were different forms of the Black Death, and they were spread in different ways, though they were caused by the same organism. The Bubonic Plague was a form carried by such animals as rats and the fleas that lived on them, both of which exhibited symptoms of the disease. When a flea bit an infected rat, it would get sick; subsequently, if it bit another rat or a human being, it would vomit as it bit, infecting that animal or person.