The Black Death is best known for the catastrophic wave of plague that swept through Europe between 1347 and 1353, killing millions of people. But the disease did not vanish once that initial disaster passed. Plague returned again and again for more than four centuries, repeatedly disrupting cities, economies, and societies across Europe and surrounding regions.
A study led by researchers at the University of Tartu is now offering a much more detailed look at what happened during those centuries. By analyzing DNA from the plague bacterium preserved in archaeological human remains, scientists were able to reconstruct how the disease spread, evolved, and repeatedly reappeared long after the Black Death. The team reconstructed 26 genomes of Yersinia pestis, the bacterium that causes plague, from human remains recovered at 11 archaeological sites in Estonia, Russia, England, the Netherlands, and Switzerland.
The samples date from the fourteenth through the eighteenth centuries, covering a large portion of the period known as the Second Plague Pandemic. The genetic evidence suggests that plague did not simply survive in one place and repeatedly spread outward from a single source. Instead, the disease appears to have resurfaced in different parts of Europe over hundreds of years, potentially creating several new reservoirs where the bacterium could persist.
Estonia was repeatedly affected. Researchers found signs that plague entered the region multiple times during much of the Second Plague Pandemic, indicating that Estonia's connections with other parts of Europe also helped disease move across long distances. One of the most striking patterns appeared around 1450-1500.
During that period, plague lineages underwent a major expansion and split into three important branches. Those branches may have helped establish new reservoirs of Yersinia pestis in wild rodent populations. Climate may also have influenced this expansion.
The researchers point to the Great Renaissance Drought as one possible factor. Studies of modern plague systems have shown that changes in climate can strongly affect outbreaks among wild rodents, which act as natural hosts for the bacterium. "We found evidence for repeated introductions of plague into Estonia starting already in the late 14th century and identified several previously unknown genetic lineages, both in urban and rural settings," said senior author Prof.
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