What is a Bubonic Plague?

Bubonic Plague is an infectious disease of animals and humans caused by a bacterium named Yersinia pestis. People usually get plague from the bite of a rodent flea that is carrying the plague bacterium or by handling an infected animal. Millions of people in Europe died from plague in the Middle Ages, when flea-infested rats inhabited human homes and places of work. Today, modern antibiotics are effective against the plague, but if an infected person does not seek treatment promptly, the disease is likely to cause illness or death. Despite its epidemic history and the deaths of millions of people, the public still knows little about the disease.

Due to its bacterial nature, Yersinia pestis has proven difficult to classify; however, new technologies have allowed researchers to classify it more accurately in the past several years. Y. pestis is a prokaryotic bacterium and, therefore, is of the kingdom Monera. Taxonomists formerly classified its genus, Yersinia, in the family Pasteurellaceae, but based on DNA similarities to Escherichia coli, the Yersinia group became members of the Enterobacteriaceae family. Numerous biochemical differences among its members are the basis of differentiation among the members of the family Enterobacteriaceae. More recently, biologists have applied nucleic acid techniques to assist in the definition of genera and species within this family; hence, as more techniques are applied, newly defined genetic relationships have to lead to changes in classification. Though there are 11 named species in the genus Yersinia, doctors consider only three significant human pathogens: Y. pestis, the agent of plague, Y. pseudotuberculosis, and Y. enterocolitica. Y. pseudotuberculosis is the closest genetic relative to Y. pestis but can be distinguished from the plague bacteria by its clinical manifestations and by laboratory test results. Both Y. pestis and Y. pseudotuberculosis do not frequently infect humans in contrast t