DNA analysis of medieval teeth pinpoints possible origin of the Bubonic Plague second wave in modern Kyrgyzstan

(CN) — The most devastating organism mankind has ever faced is the bacteria Yersinia pestis, the force behind the devastating bubonic plague. Plague bacteria found on the remains of individuals marked as victims of pestilence marks a potential time and place of origin for the deadly second pandemic wave, according to research published Wednesday in Nature.

“We found that the ancient strains from Kyrgyzstan are positioned exactly at the node of this massive diversification event. In other words, we found the Black Death’s source strain and we even know its exact date,” said Maria Spyrou, lead author and researcher at the German University of Tübingen, in a statement.

The first bubonic plague pandemic was recorded in Constantinople in the sixth century. The second plague pandemic, which began with the Black Death, hit Europe in the 14^th century and continued in several dozen other waves through the early 19^th Century. Throughout this 500-year reign, the plague claimed the lives of roughly 60% of the people living in Western Eurasia.

With the plague surviving the centuries in wild rodent populations around the world, a third pandemic wave emerged in the mid-19th century.

A team of archaeologists and geneticists from Germany, Italy, Russia and the United Kingdom analyzed teeth from the remains of seven individuals buried in two Eurasian cemeteries, Kara-Djigach and Burana, marked for victims of pestilence.

The Kunstkamera Peter the Great Museum of Anthropology and Ethnography in St. Petersburg allowed researchers to sample ancient DNA from seven teeth, representing seven individuals buried from 1338 to 1339, and excavated in the 1880s. DNA analysis was carried out at the Max Planck Institute in Munich, Germany.

By confirming the presence of the plague bacteria, researchers added support for the emergence of the second pandemic wave from the Chüy Valley near Lake Issyk-Kul of modern-day Kyrgyzstan. From there, the bacteria hit spread in a star-like formation along four major genetic lineages, which Phil Slavin, a historian at the University of Sterling in Scotland, described as a great polytomy, or "big bang" event.

While there is vast variation between infectious disease outbreaks, Yersinia pestis underwent this evolutionary explosion just before the Black Death wave devastated Europe.

“This could be one important lesson for understanding the history of epidemics,” said Slavin told Courthouse News via email “Their outbreaks may be associated with some major evolutionary event. However, plague is only one example; much more similar work needs to be done with other epidemic diseases, in order to establish that point."

In his ongoing research, Slavin is studying other possible pandemic triggers, including the ecological and climatic context in the Tian Shan region at the time.

“While it does not pretend to solve the mystery of triggers initiating that outbreak, it will offer some preliminary insights, and open the floor for new questions,” Slavin explained. “Another important question is how did the same plague wave spread from Central Asia into Europe in the 1340s?”

In the paper, researchers point to the local Christian community at Kara-Djigach, which carried out long-distance trade across Eurasia, supporting the notion that the disease spread along trade routes.

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