Plague Home > Causes of Bubonic Plague

The causes of bubonic plague are the Yersinia pestis bacteria. In most cases, the bacteria are transmitted through the bite of an infected rodent or flea. Other carriers of the bacteria include lice, prairie dogs, and chipmunks. Although it is extremely rare, there have been instances where the causes of bubonic plague were through human-to-human transmission.

Causes of Bubonic Plague: An Overview

Bubonic plague is the most common form of plague. The causes of bubonic plague are bacteria called Yersinia pestis. This bacteria also causes the other two forms of plague: septicemic plague and pneumonic plague (see Types of Plague).

Causes of Bubonic Plague: Yersinia Pestis

Yersinia pestis bacteria are usually only found in certain parts of the world, such as Africa, Asia, and South America. Approximately 1,000 to 3,000 cases of bubonic plague are reported each year. Between 10 to 20 of these cases are in the United States, most commonly in rural areas of the Southwest.
Yersinia pestis is most commonly found in rats, but can also occur in other animals. Other animals known to carry Yersinia pestis can include:
  • Lice
  • Fleas
  • Chipmunks
  • Mice
  • Prairie dogs
  • Dogs
  • Cats
  • Squirrels
  • Wood rats.
(Click Bubonic Plague Pictures for examples of animals that cause bubonic plague.)

How Are Causes of Bubonic Plague Transmitted?

The bacteria that are the causes of bubonic plague are typically transmitted through the bite of an infected flea or rodent. In rare cases, Yersinia pestis bacteria on a piece of contaminated clothing or other material used by an infected person can enter through an opening in your skin. Bubonic plague is rarely spread from person to person.
Once inside the body, Yersinia pestis travel to the lymph nodes and begin to multiply. (The lymph or lymphatic system is a major component of your body's immune system. The organs within the lymphatic system are the tonsils, adenoids, spleen, and thymus.)
Within two to six days of exposure, bubonic plague symptoms will develop, such as:
  • Weakness
  • Headache
  • Fever
  • Chills
  • Swollen, tender lymph glands (called buboes, hence the name bubonic).
Written by/reviewed by:
Last reviewed by: Arthur Schoenstadt, MD
Last updated/reviewed:
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