Were Rats Actually Responsible for Spreading the Black Death?

The Black Death killed at least 75 million people in Europe between 1347 and 1351, making it one of the worst pandemics in human history. Some put the death toll as high as 200 million. The plague was tied to the the bacterium Yersinia pestis, supposedly spread by rats. But a 2018 study conducted by scientists at the University of Oslo and the University of Ferrara suggests that it is more likely that human “ectoparasites” -- such as body lice and human fleas -- actually caused the deadly epidemic.

A plague that still lives among us:

• The researchers studied data from a series of outbreaks in Europe called the "second plague pandemic," and tracked how plagues were spread -- by rodents, by airborne transmission, or by humans.
• Pointing to how quickly the plague spread, the researchers found that the human parasite model best reflected death rates in seven of the nine regions studied.
• "Plague is undeniably a disease of significant scientific, historic and public interest, and is still present in many parts of the world today," the researchers said.