The New Dictionary of Cultural Literacy, Third Edition. 2002.
bubonic plague
(byooh-BON-ik, booh-BON-ik PLAYG) A highly contagious disease, usually fatal, affecting the lymphatic system. The bubonic plague is caused by bacteria transmitted to humans by rat-borne fleas.
From 1347 to 1351, a disease known as the Black Death, similar to the bubonic plague, entered Europe from Asia and killed a large percentage of the population, sometimes wiping out entire towns. It caused widespread social changes in Europe.