Bubonic Plague Overview

A person with the bubonic plague has a serious infection caused by the bacteria, Yersinia pestis. The bacteria is transmitted to humans by rat flees, ticks and lice, but can also be spread from infected animals. The most common symptom is tender, swollen lymph glands. The bacteria can infect the skin, throat, lungs or brain. Bubonic plague is very rare: less than 10 cases of plague occur in the US each year.

What is bubonic plague?

Bubonic plague is a zoonotic disease, circulating mainly among small rodents and their fleas, and is one of three types of bacterial infections caused by Yersinia pestis (formerly known as Pasteurella pestis), which belongs to the family Enterobacteriaceae. Without treatment, the bubonic plague kills about two thirds of infected humans within 4 days.

The term bubonic plague is derived from the Greek word βουβών, meaning "groin." Swollen lymph nodes (buboes) especially occur in the armpit and groin in persons suffering from bubonic plague. Bubonic plague was often used synonymously for plague, but it does in fact refer specifically to an infection that enters through the skin and travels through the lymphatics, as is often seen in flea-borne infections.

Bubonic plague—along with the septicemic plague and the pneumonic plague, which are the two other manifestations of Y. pestis—is generally believed to be the cause of the Black Death that swept through Europe in the 14th century and killed an estimated 25 million people, or 30–60% of the European population. Because the plague killed so many of the working population, wages rose and some historians have seen this as a turning point in European economic development.