Crack open your average history textbook, and you’ll probably find the tragic tale of the Justinianic plague, a pandemic that tore across ancient Europe and Asia between 541 and 750 A.D., claiming an estimated 25 million to 50 million lives.

The plague—a bacterial disease ferried from rodents to people via infected fleas—is widely believed to have culled the era’s Mediterranean populations by up to 60 percent. Historians have argued that its scourge altered the course of history, ushering in the demise of the eastern Roman Empire, the rise of Islam, and, ultimately, the emergence of modern Europe.

Now, new research is challenging this age-old narrative. After poring through data ranging from historical texts to pollen samples and mortuary archaeology, an international team of researchers has concluded that reports of the havoc wreaked by the Justinianic plague may have been exaggerated. The not-so-devastating disease, they contend in a paper published this week in Proceedings of the National Academy of Sciences, didn’t actually claim that many lives—and was a far cry from the empire-toppling, society-reshaping debacle it’s often made out to be.

“It's easy to assume infectious diseases in the past would have catastrophic results,” lead author Lee Mordechai, an environmental historian at Hebrew University of Jerusalem, tells CNN’s Katie Hunt. “Yet, we used every type of data set we could get our hands on [and] found no evidence in any of these data sets to suggest such a destructive outcome.”