What is the difference between Xenopsylla cheopis and bubonic plague?

*Xenopsylla cheopis* is a species of flea commonly known as the Oriental rat flea. On the other hand, bubonic plague, also known as the Black Death, is an infectious disease caused by the bacterium _Yersinia pestis_. Although *X. cheopis* was considered the primary vector or agent that transmits bubonic plague, researchers found different types of fleas can cause its transmission. Today, it is also spread when people or animals directly encounter the infectious bodily fluids of an infected animal.