The Black Death may not have been spread by rats after all

The Black Death ravaged Europe between 1347 and 1353, killing millions. Plague outbreaks in Europe then continued until the 19th century.

One of the most commonly recited facts about plague in Europe was that it was spread by rats. In some parts of the world, the bacterium that causes plague, Yersinia pestis, maintains a long-term presence in wild rodents and their fleas. This is called an animal “reservoir”.
While plague begins in rodents, it sometimes spills over to humans. Europe may have once hosted animal reservoirs that sparked plague pandemics. But plague could have also been repeatedly reintroduced from Asia. Which of these scenarios was present remains a topic of scientific controversy.
Our recent research, published in the Proceedings of the National Academy of Sciences (PNAS), has shown that environmental conditions in Europe would have prevented plague from surviving in persistent, long-term animal reservoirs. How, then, did plague persevere in Europe for so long?
Our study offers two possibilities. One, the plague was being reintroduced from Asian reservoirs. Second, there could have been short- or medium-term temporary reservoirs in Europe. In addition, the two scenarios might have been mutually supportive.
However, the rapid spread of the Black Death and subsequent outbreaks of the next few centuries also suggest slow-moving rats may not have played the critical role in transmitting the disease that is often portrayed.
The Black Death may not have been spread by rats after all