Black death was a world wide epidemic of bubonic. The plague was believed to be caused by flees that latched and bite rats resulting in wide spread of the plague. When infected rats came in contact with humans they contaminated food and water spreading the disease. Because of the decline of rats the flees where in desperate need of a new host. They thus turned to human as they breeding grounds infecting humans with painful buboes filled with puss resulting in swelling in groins, under armpits on lymph nodes and on the neck. Early recovery was possible but once the the pulmonary epidemic or pneumonic plague spread it made it impossible to survive. The plague appeared in different forms such as the pulmonary or pneumonic plague which attacked the lungs and the septicaemic plague that attacked the blood stream,