Bubonic plague

Alternative names
Plague; Pneumonic plague; Septicemic plague

Plague is an infection caused by the organism Yersinia pestis. It is carried by wild rodents and transmitted to humans.

Causes, incidence, and risk factors

Plague is transmitted among rodents and to humans by flea bite or ingestion of the feces of fleas. It can also be transmitted from human to human when a plague victim develops pneumonia and spreads infected droplets by coughing. An epidemic may be started this way.

Plague is rare in the United States, but areas where the disease is known to occur include parts of California, Utah, Arizona, Nevada, and New Mexico.

There are two types of plague, bubonic and pneumonic. The incubation period is 2 to 10 days but may be as short as a few hours for pneumonic plague.

Risk factors for plague include a recent flea bite; and occupational or environmental exposure to rodents (especially rabbits, squirrels, or prairie dogs; or scratches or bites from infected domestic cats).


  • Sudden onset of high fever  
  • Chills  
  • General discomfort, uneasiness, or ill feeling (malaise)  
  • Muscular pains  
  • Severe headache  
  • Smooth, oval, reddened, painful swellings of swollen lymph glands called buboes in the groin, armpits, neck, or elsewhere in the body. Pain may occur in the area before the swelling; the most common area is in the groin  
  • Seizures


  • Severe cough  
  • Frothy, bloody sputum  
  • Difficulty breathing


  • Fever  
  • Extreme illness  
  • Nausea, vomiting, diarrhea, and abdominal pain  
  • Low blood pressure  
  • Blood clotting problems  
  • Failure of several or all organ systems

Signs and tests
These tests may indicate a plague infection:

  • Culture of bubo  
  • Culture of sputum  
  • Blood culture  
  • Lymph node culture


Immediate treatment with antibiotics such as streptomycin, chloramphenicol, or tetracycline is indicated. Oxygen, intravenous fluids, and respiratory support are additional treatments.

Patients with pneumonic plague are strictly isolated from other patients. People who have had contact with anyone infected by pneumonic plague are observed closely and are given antibiotics as a preventive measure.

Note: Oral tetracycline is usually not prescribed for children until after all the permanent teeth have erupted. It can permanently discolor teeth that are still forming.

Expectations (prognosis)
Half of bubonic plague victims die if not treated, and almost all victims of pneumonic plague die if not treated. Treatment reduces the death rate to 5%.


Some complications include septicemia (blood poisoning).

Calling your health care provider
Call your health care provider if symptoms develop after exposure to fleas or rodents, especially if you live in or have visited in an area where plague occurs.

Rat control and surveillance of the disease in the wild rodent population are the main measures used to control the risk of epidemics. A vaccination is available for high-risk workers, but its effectiveness is not clearly established.

Johns Hopkins patient information

Last revised: December 8, 2012
by Brenda A. Kuper, M.D.

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