Pneumonic Plague

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What is plague?

Plague is an uncommon infectious disease of animals and humans caused by Yersinia pestis (Y. pestis) bacteria. Y. pestis is present in wild rodents and their fleas in many areas around the world, including most of the western United States.

Types of plague

Plague can be transmitted and cause illness in one or more of these forms:

  • When the Y. pestis bacteria enters the body through the bite of an infected flea or through a cut or break in the skin, the resulting disease is called bubonic plague. “Buboes” are swollen painful lymph nodes. Bubonic plague is the most common form of the disease and untreated it may progress to septicemic plague (see below).
  • When Y. pestis bacteria accumulate in the bloodstream, septic shock occurs and the resulting disease is called septicemic plague.
  • When Y. pestis bacteria are inhaled, they lodge in the lungs and the resulting disease is called pneumonic plague. Pneumonic plague is of particular concern because it can be spread from person to person.

How is pneumonic plague spread? What are the symptoms?

Pneumonic plague occurs when the Y. pestis bacterium is inhaled. The disease may be spread through face-to-face contact when an infected person coughs or sneezes. Because it enters the body by being inhaled, pneumonic plague could be spread intentionally if the bacteria were put into aerosol form.

The symptoms of pneumonic plague begin one to four days after exposure to the bacteria. The symptoms include fever, headache, weakness and a bloody or watery cough due to infection of the lungs (pneumonia). The pneumonia rapidly becomes worse and — without early treatment — it can be fatal.

Preventive measures

If you have symptoms, consult a healthcare provider as soon as possible. If you believe you have been intentionally exposed to pneumonic plague, you should contact law enforcement officials immediately.

There is no vaccine against pneumonic plague. Antibiotics are used to prevent illness in those who have been exposed to pneumonic plague.

Treatment for pneumonic plague

Early treatment with appropriate antibiotics is essential because untreated plague — especially the pneumonic form — is almost always fatal. You should use antibiotics to prevent or treat plague only under the direction of your healthcare provider or local health department.

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DOH Pub 821-023
Revised - March 2008
Reviewed annually

This document was produced in cooperation with the
Emergency Management Division of the Washington State Military Department.