THE BUBONIC PLAGUE Plague, was a term that was used in the Middle Ages to describe all fatal epidemic diseases, but now it is only applied to an infectious, contagious disease of rodents and humans. In humans, plague occurs in three forms: bubonic plague, pneumonic plague, and septicemic plague. The best known form is the bubonic plague and it is named after buboes, or enlarged, inflamed lymph nodes, which are characteristics of the plague in the groin or neck or armpit. Bubonic plague can only be transmitted by the bite of any of numerous insects that are normally parasitic on rodents and that seek new hosts when the original host dies.