The Plague (also known as the Black Death) raged across Europe between 1346 and 1353, and reached its peak between 1348 and 1350. It wiped out between one-third and one-half of Europe’s population.
The cause of the Black Death is believed to have been the Bubonic Plague. The first symptoms were usually large boils or welts, and were soon followed by a high fever and vomiting of blood. A victim usually died within two to seven days after first manifesting symptoms.
The Plague also caused enormous social and religious upheaval. Mainstream religion was not protecting people, and some turned to more radical religious orders, like the Flagellants, who believed people had to atone for their sins by flagging themselves in public (this practice actually tended to weaken a person’s resistance and make him/her more vulnerable to the disease).
Another societal consequence of the Black Death is increased rights for the peasantry. With far fewer laborers, the peasants were able to press for more security.