Bureau of Communicable Disease

Plague (Pneumonic plague, bubonic plague)

What is plague?

Plague is a bacterial disease caused by Yersinia pestis. Wild rodents, especially ground squirrels and prairie dogs, are the natural reservoir for plague. Rats, wild rodents, cats, and dogs can become infected with plague and the disease is occasionally transmitted to people by fleas.

Who gets plague?

Plague is extremely rare in the United States, where the small number of reported cases in recent years have been limited to the Western states. Plague occurs in areas where infection of wild rodents is common, including South America, parts of Africa, and South Asia.

Are there different kinds of plague?

Yes. Bubonic plague gets its name from the enlarged and tender lymph glands, or nodes (called "buboes" during the 14th century, when the disease ravaged Europe). Pneumonic plague gets its name from its pneumonia-like symptoms.

How is plague spread?

Bubonic plague is transmitted primarily by the bite from infected fleas; however, transmission can occur by bites or scratches from infected wild rodents and cats, or contact with tissue from infected animals. Pneumonic plague is far more contagious because it is spread through the air by sneezing or coughing.

What are the symptoms of plague?

Initial symptoms include fever, chills, muscle aches, headache, nausea, vomiting, diarrhea, abdominal pain, and extreme exhaustion. Swollen and tender lymph nodes near where the infected flea bit the person are typical of bubonic plague. Pneumonic plague usually presents with a cough, bloody sputum and difficulty breathing.

How soon after infection do symptoms appear?

The incubation period for both types of plague is 2 to 7 days after exposure to the bacteria.

How is plague diagnosed?

Plague is diagnosed by isolating the bacteria from sputum, blood, spinal fluid, or infected glands.

What is the treatment for plague?

Bubonic plague can be effectively treated with certain widely-available antibiotics. If untreated, it can be fatal in approximately 50-60% of infected persons. Pneumonic plague is almost always fatal if not treated quickly after the onset of symptoms.

Does past infection with plague make a person immune?

Immunity after plague recovery is variable, and may not provide complete protection.

How can plague be prevented?

When traveling in areas where plague is common, it is important to avoid being bitten by infected fleas, or having contact with plague-infected animals, or persons infected with pneumonic plague. Patients with pneumonic plague should be quarantined until 3 full days of antibiotic treatment have been administered. Buildings should be rat-proofed, with appropriate storage and disposal of food, garbage, and refuse. Dogs and cats in such areas should be treated with insecticides to prevent flea infestation.

Last updated March 2003