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Bubonic Plague

A Relatively Rare Disease With Bioterrorist Appeal

Apr 6, 2009 Stephen Allen Christensen

For most people, the Black Death is a tale from history books. This disease still occasionally breaks out in some areas, and it can still kill.

Even casual students of history have heard of the Black Death of the Middle Ages, a massive epidemic that may have decimated as much as 60% of Europe’s population. Most scientists attribute the cause of this pandemic to a bacterial organism, Yersinia pestis.

Y. pestis primarily infects wild rodents such as rats, mice, squirrels, prairie dogs, and marmots. The infection is most commonly spread to humans through the bites of fleas that have acquired the organism from these rodents.

In the US, over 90% of human plague occurs in the southwestern states (New Mexico, Arizona, California, and Colorado). In such endemic areas (i.e., places where the disease is more common, but not at epidemic levels), people can also be infected by exposure to the bites or secretions of household pets.

At least three major forms of plague can occur, with some overlap between these syndromes. Other, less common forms of the disease have been described as well (e.g., pestis minor, a less severe form of bubonic plague; pharyngeal plague; plague meningitis).

Major Types of Plague and Their Signs and Symptoms

Bubonic plague: The most common form of plague, characterized by massive swelling of lymph nodes (buboes) in various areas of the body (groin, armpits, neck, etc.). Incubation period from time of exposure ranges from a few hours to two weeks. High fever (sometimes to 106º), rapid pulse, hypotension, restlessness, delirium, confusion and loss of coordination then occur abruptly. Swollen nodes are exquisitely tender and may open and drain after a week or so. Liver and spleen enlargement are not uncommon. Approximately 60% of untreated patients die.
Pneumonic plague: Incubation period is two to three days, followed by rapid onset of high fever, chills, rapid heart rate, and severe headache. Cough develops gradually over a day or two. Sputum progresses from clear to blood-tinged to uniformly pink or frankly bloody (“raspberry syrup”). Respiratory distress develops quickly—with mortality reaching nearly 100% within 48 hours in untreated patients.
Septicemic plague: Usually accompanies bubonic or pneumonic plague as a fulminant, rapidly-progressive illness, but can be fatal on its own before either bubonic or pneumonic signs are predominant. Incubation period is variable, but symptoms are similar to other forms. About 40% of patients with septicemic plague also develop severe abdominal pain, probably due to involvement of lymph nodes in the abdominal cavity. Mortality in untreated patients is essentially universal.

Diagnosis and Treatment of Plague

Diagnosis of plague may be delayed due to its relative rarity outside of endemic areas. Physicians who are unfamiliar with plague may not recognize it in a timely fashion.

Staining of Y. pestis from sputum or from fluid aspirated from lymph nodes is the quickest means of diagnosis. Antibody titers and cultures of blood, sputum and lymph node aspirates are useful. PCR and immunofluorescent staining are diagnostic, if they are available.

Antibiotic therapy for pneumonic or septicemic plague (doxycycline, fluoroquinolones, streptomycin, etc.) must begin within 24 hours of symptom onset. Appropriate treatment reduces mortality to less than 5%.

All patients with plague must be isolated; those with pneumonic plague require strict respiratory isolation due to risks to other individuals.

Persons traveling to areas where plague is endemic should consider prophylaxis with doxycycline. Prior vaccination for plague does not confer 100% protection.

The diagnosis of plague is relatively rare in the United States, although sporadic outbreaks occur in endemic areas. Unfortunately, Yersinia pestis has significant potential as an agent of bioterrorism; therefore, physicians and the general population should be cognizant of this disease’s signs and symptoms and the necessity for prompt treatment.

The copyright of the article Bubonic Plague in General Medicine is owned by Stephen Allen Christensen. Permission to republish Bubonic Plague in print or online must be granted by the author in writing.