Overview
Bubonic plague is an illness caused by the bacterium
Yersinia pestis. This bacterium is carried by a certain type of flea, commonly known as a rat flea, which infects humans and animals. Humans can get bubonic plague from the bite of an infected flea, from the bite of an animal infected with
Y. pestis, or from handling the carcass of an infected animal. The name of the illness comes from the classic skin lesions that develop in persons infected with
Y. pestis: large, swollen lymph nodes called buboes.
Bubonic plague is easily treated with modern antibiotics, if the diagnosis is made quickly; this was not the case in the Middle Ages, when millions of people died from a bubonic plague epidemic. Today, bubonic plague exists around the world but in very small numbers. In the United States, there are 10–15 cases per year. Mortality, in disease that has undergone treatment, is about 5–15%; mortality, in disease that has been untreated, approaches 60%.
Y. pestis has the potential to be used as a weapon of bioterrorism; if this were to happen, the bacterium would likely be dispersed as an aerosol and would cause a different form of plague, known as pneumonic plague. Unlike bubonic plague, pneumonic plague is highly contagious among humans (bubonic plague is
not contagious among humans), and mortality is even higher. In the case of a bioterrorism attack with
Y. pestis, the United States maintains a stockpile of appropriate antibiotics to treat plague.
