Plague: from natural disease to bioterrorism

Abstract

Yersinia pestis is the causative agent of plague, an enzootic vectorborne disease usually infecting rodents (rats) and fleas. Humans can become infected after being bitten by fleas that have fed on infected rodents. In humans, the disease usually occurs in the form of bubonic plague. In rare cases, the infection spreads to the lungs via the bloodstream and causes secondary pneumonic plague. Person-to-person transmission has been described for pneumonic plague but is rare in primary bubonic plague. Bubonic plague can usually be treated successfully with antibiotics; however, pneumonic plague develops rapidly and carries a high fatality rate despite immediate treatment with antibiotics. Plague is also recognized as a potential agent of bioterrorism. It has been used, or considered for use, as a biologic weapon on several occasions. It is important for the medical community to be familiar with the epidemiology, diagnosis, and symptoms of plague so it can deliver an appropriate and calm response should the unthinkable happen.

Figure 1

The plague in Naples. Courtesy of the National Library of Medicine.

Figure 2

The plague doctor (German woodcut, 1650s). Courtesy of the National Library of Medicine.

Figure 3

Dr. Alexandre Yersin in front of the National Quarantine Station, Shanghai Station, 1936. This was where Dr. Yersin first isolated and described Pasteurella pestis, the old term used for Yersinia pestis. Photo by Antoine Danchin; used courtesy of the Pasteur Research Centre and the Public Health Image Library.

Figure 4

Dark stained bipolar ends of Yersinia pestis can clearly be seen in this Wright's stain of blood from a plague victim (1993). Photo from CDC; used courtesy of the Public Health Image Library.

Figure 5

Yersinia pestis on sheep blood agar, 72 hours. Y. pestis grows well on most standard laboratory media. After 48 to 72 hours, it shows gray-white to slightly yellow opaque raised, irregular “fried egg” morphology; alternatively, colonies may have a “hammered copper” shiny surface. Photo by Larry Stauffer, Oregon State Public Health Laboratory; used courtesy of the CDC and the Public Health Image Library.

Figure 6

Oriental rat flea. Photo from the World Health Organization; used courtesy of the Public Health Image Library.

Figure 7

Plague patient with an axillary lymphadenopathy. Courtesy of the Public Health Library of Medicine, CDC.

Figure 8

This patient presented with symptoms of plague that included gangrene of the hand causing necrosis of the fingers. Photo from CDC/Dr. Jack Poland; used courtesy of the Public Health Image Library.

Figure 9

Chest x-ray in a patient with secondary pulmonary plague. Photo from CDC/Dr. Jack Poland; used courtesy of the Public Health Image Library.

Figure 10

This photomicrograph illustrates the histopathologic changes in lung tissue in a case of fatal human pneumonic plague (hematoxylin and eosin stain, × 160). Note the moderate suppurative pneumonia including the presence of many polymorphonuclear leukocytes, capillary engorgement, and intraalveolar debris, all indicative of an acute infection. Photo from CDC/Dr. Marshal Fox; used courtesy of the Public Health Image Library.