Estonia faced repeated plague waves over centuries
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Researchers at the University of Tartu in Estonia analyzed ancient plague bacteria to understand how the disease spread across Europe from the 1300s to the 1700s.
The team examined genetic material from 26 plague bacterium samples recovered from archaeological sites in Estonia, Russia, England, the Netherlands, and Switzerland. They discovered the plague repeatedly entered Estonia during the second plague pandemic, rather than being a single event.
The study identified previously unknown lineages of Yersinia pestis, the bacterium causing plague, and showed strains spread quickly across Europe through trade and contact. Researchers connected genetic changes in the bacteria to climate events like the Great Renaissance Drought of 1540, which impacted rodent populations that carry the disease. They also developed a new method combining genetic analysis with archaeological dating to pinpoint the timing of outbreaks more accurately.
This approach allowed them to link plague outbreaks to specific historical events, including the Thirty Years' War and the Great Northern War, revealing how military conflicts aided the disease’s spread. The study confirmed that wars and troop movements facilitated the transmission of Yersinia pestis, as seen during the 1710 siege of Tallinn where soldiers and civilians alike succumbed to the plague.
Though plague is no longer a major threat in Europe, Yersinia pestis still exists in wild rodents globally, and understanding its historical patterns can inform modern disease monitoring and prevention.
