In many elementary schools, students are introduced to the idea that rats spread one of the deadliest diseases in human history – the Bubonic plague. It was told in history classes that rats carried fleas, which carried the bacteria responsible for the Bubonic plague. These rodents prospered in the poor sanitary conditions of European cities and went on to spread the disease to humans throughout Europe decimating up to 50% of the population.

Recent news reports have now attempted to exonerate rats from their role in the Bubonic plague – a result that calls for the rewriting of history books. A new study claims that the plague bacteria were introduced into Europe countless times instead of persisting there in local rodent populations. Tree-ring records were used to reconstruct the weather patterns in along the silk trade route between Europe in Asia to conclude that weather fluctuations in Asia preceded introductions of the plague into Europe. It is predicted that these weather fluctuations would be ideal for Asian gerbil population booms, which would result in more fleas and thus, more plague bacteria with the ability to spread to Europe.

The idea that plague traveled along trade routes isn’t new, but the reliance on extrapolating climate data from tree rings to gerbil populations is a big leap. Even so, we can only speculate at how this would lead to the spread of plague-carrying fleas to Europe. However, even if weather fluctuations and gerbils did somehow lead to the introduction of plague to Europe, it is important to note that rats would have still been the primary spreaders following plague’s introduction to Europe. If anything, rats and gerbils were in on this diabolical plot together.

Managing Correspondent: Joseph Timpona

Acknowledgements: Many thanks to Tracy Kambara, a graduate student in the Biological and Biomedical Sciences program at Harvard University for commentary on the topic.

Original article: Climate-driven introduction of the Black Death and successive plague reintroductions into Europe

Media coverage: Plague’s origins ratted out: GERBILS not rats were the main cause of the Black Death

After 8 centuries, rats exonerated in spread of Black Death. Gerbils implicated