It may start out as a terrible headache, and then turn into chills and a high fever. Nausea, vomiting, back pains, and soreness of the limbs are soon to follow. Bright light will become hard to withstand. All of this came and went within three to four days. These are symptoms millions of people suffered during the fourteenth century. The bubonic plague, also known as the Black Death or Black Plague, was one of the most horrible outbreaks of that time period. (Death Defined)
Before death, swellings of the lymph nodes called buboes appeared, giving the disease its name. These inflammations were hard, painful, and burned or irritated the skin. These growths could expand to the size of an orange. (Death Defined) "The disease at this point began to take on the qualities of a deadly sickness, and the body would be covered with dark and livid spots, which would appear in great numbers on the arms, the thighs, and other parts of the body; some were large and widely spaced while some were small and bunched together.
And just like the gavaciolli (a commoner's term for the swellings) earlier, these were certain indications of coming death (Boccaccio: The Decameron)." The swellings would expand until they burst, causing death soon after.
The disease was spread by the bacteria Yersinia pestis and transmitted by fleas and infected rats commonly found on the streets of many European cities in the fourteenth century. The fleas would infest the infected rat and spread the disease to humans and other rats by regurgitating the contaminated blood into the bloodstream of the new host. Many at the time did not know this was the means of dispersal for the disease and insisted on other ways of prevention, instead of trying to stay away from the rats.