Lifespan's A - Z Health Information Library

Plague is a severe, and potentially deadly, infection. It is caused by the organism Yersinia pestis. Wild rodents, like rats, spread the disease to humans.

Plague is spread among rodents by a flea bite. Humans may get the plague when they touch or eat the infected animal, or when they come in contact with it's feces. 

Certain forms of the plague can be spread from human to human. When a plague victim with pneumonia coughs, microscopic droplets carrying the infection move through the air. Anyone who breathes in these particles can catch the disease. An epidemic may be started this way. (In the Middle Ages, massive plague epidemics killed millions of people.)

Plague is rare in the United States, but has been known to occur in parts of California, Utah, Arizona, Nevada, and New Mexico.

There three most common forms of plague are:

• Bubonic -- an infection of the lymph nodes.
• Pneumonic -- an infection of the lungs.
• Septicemic -- an infection of the blood.

The incubation period is typically 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 exposure to rodents, especially rabbits, squirrels, or prairie dogs, or scratches or bites from infected domestic cats.

Bubonic Plague: Symptoms appear suddenly, usually after 2-5 days of exposure to the bacteria.

• Sudden onset of high fever
• The classic sign is a smooth, painful swelling of a lymph gland(s), called a buboe. The most common area is the groin, but swollen glands may also occur in the armpits or neck. Pain may occur in the area before the swelling.
• Chills
• General discomfort or ill feeling (malaise)
• Muscular pain
• Severe headache
• Seizures

Pneumonic Plague: Symptoms begin abruptly, typically 2-3 days after exposure.

• Severe cough
• Frothy, bloody sputum
• Difficulty breathing

Septicemic Plague: This blood infection may cause death even before the signs of bubonic or pneumonic plague occur.

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

These tests may indicate a plague infection:

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

Patients with the plague need immediate treatment withing 24 hours of initial symptom development, or death may be unavoidable. Treatment consists of antibiotics such as streptomycin, chloramphenicol, or tetracycline. 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.

Oxygen, intravenous fluids, and respiratory support are usually also prescribed.

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.

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%.

Call your health care provider if symptoms develop after exposure to fleas or rodents, especially if you live in or have visited 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.

Kool JL. Risk of person-to-person transmission of pneumonic plague. Clin Infect Dis. 2005 Apr 15;40(8):1166-72.

Cobbs CG, Chansolme DH. Plague. Dermatol Clin. 2004 Jul;22(3):303-12, vi.

Josko D. Yersinia pestis: still a plague in the 21st century. Clin Lab Sci. 2004 Winter;17(1):25-9.