Bubonic plague is caused by Yersinia pestis, also known as plague bacteria. Yersinia pestis is a type of Gram-negative bacteria found in certain parts of the world. It causes about 1,000 to 3,000 cases of plague each year.

 

Usually, bubonic plague is contracted through the bite of an infected flea or rodent. In rare cases, Yersinia pestis bacteria enter through an opening in your skin, whether from a piece of contaminated clothing or other material used by an infected person. Bubonic plague is rarely spread from person to person. Once inside the body, Yersinia pestis bacteria travel to the lymph nodes and begin to multiply, which can lead to symptoms of bubonic plague.