Yersinia Pestis

Genus: Yersinia
Species: pestis, enterocolitica

Yersinia pestis is responsible for bubonic plague which has periodically become pandemic throughout recorded history.

During the sixth century, the plague ravaged the known world for at least fifty years, causing 100 million deaths.

The "Black Death" devastated Europe, again, during a five-year-period in the fourteenth century when approximately 25 million people died.  (At the time, that was roughly twenty-five percent of Europe's population.)

Credits

Image, Center for Disease Control.