Yersinia pestis facts for kids

Yersinia pestis is a tiny living thing called a bacterium. It is shaped like a rod, which is why it's also called a bacillus. This bacterium is famous for causing the plague, a very serious disease.

There are three main types of plague that Y. pestis can cause:

• Bubonic plague: This type causes swollen, painful lymph nodes called "buboes."
• Septicemic plague: This happens when the bacteria spread through the blood.
• Pneumonic plague: This is the most serious type, affecting the lungs. It can spread from person to person through the air.

These forms of plague have caused many deaths in history. They are believed to be the reason for the terrible Black Death. The Black Death was a huge epidemic (a widespread disease outbreak) that killed about one-third of the people in Europe between 1347 and 1353.

Discovery of Yersinia pestis

Who Found the Germ?

The Y. pestis bacterium was discovered by a doctor named Alexandre Yersin. He found it during a plague outbreak in Hong Kong in 1894.

Yersin's Work

At the time, Dr. Yersin was working for the Pasteur Institute. He was able to identify this tiny germ as the cause of the plague.

Name Change

When it was first found, the bacterium was called Pasteurella pestis. Later, in 1967, its name was changed to Yersinia pestis to honor Dr. Yersin.

Types of Yersinia pestis

Scientists currently know about three different types, or varieties, of Y. pestis. These varieties are similar but have small differences.

Yersinia pestis and the Black Death

The Big Question

For a long time, historians have wondered if Y. pestis was truly the only cause of the Black Death. Some thought the Black Death spread too quickly for this bacterium to be the only reason.

What DNA Tells Us

However, scientists have found DNA from Y. pestis in the teeth of some people who died during the Black Death. This discovery strongly suggests that Y. pestis played a big part in at least some of the plague outbreaks in Europe. It might not have been the only factor, but it was definitely involved.

Images for kids

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  An Oriental rat flea (Xenopsylla cheopis) infected with the Y. pestis bacterium. The dark mass in its gut is the bacteria. When the flea tries to feed on an uninfected animal, the bacteria can be spread into the wound, causing infection.

See also

In Spanish: Yersinia pestis para niños