Plague

Article By:

Palmer, Darwin L. Infectious Disease Division, Department of Medicine, Veterans Administration Hospital Medical Center, University of New Mexico School of Medicine, Albuquerque, New Mexico.

Last reviewed:June 2019

DOI:https://doi.org/10.1036/1097-8542.521100

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• Plague, published June 2014:Download PDF Get Adobe Acrobat Reader

An infectious disease of humans and other mammals, especially rodents, caused by the bacterium Yersinia pestis. Flea-borne plague (see illustration), which is caused by the bacterium Yersinia pestis, is a serious and historically important disease. There are three main clinical forms of infection: bubonic (which infects lymph nodes), pneumonic (which infects lungs), and septicemic (which infects blood vessels). The most common form is bubonic plague. Also known as the Black Death during the Middle Ages, this extraordinarily acute disease is believed to have killed more than 200 million people over the course of human history. In the past, explosive urban epidemics of plague occurred as the result of dense populations of infected city rats living closely with humans. The disease then was spread both by infected rat fleas and by transmission between humans. During these outbreaks, as much as 50% of the European population died. Today, the sylvatic (wild-animal) form persists in more than 200 species of rodents throughout the world, and contact with wild rodents and their fleas leads to sporadic human disease. See also: Epidemic; Infection; Infectious disease; Medical bacteriology; Microbiology; Rodentia; Yersinia; Zoonoses

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