Ancient DNA recovered from plague victims buried in Germany reveal that the plague-causing bacterium, Yersinia pestis, persisted in Europe from the 14th to 17th century. The pathogen’s host however, remains a mystery. The findings are published in PLOS ONE this week.
The first plague pandemic, which occurred from the 6th to 8th century, was called Plague of Justinian after the Byzantinian emperor Justinian I. The second plague pandemic lasted from the 14th to 17th century, peaking in Europe between 1346 and 1353. This was known as the Black Death. Millions of people were killed during these two pandemics, and one of the biggest unanswered questions about both is how they could have continued for several hundred years.
Some researchers think that the plague agent had to have been continuously reintroduced into Europe from central Asia in multiple waves along trade routes (like the Silk Road). Others argue that the plague agent persisted long-term in Europe in a host such as lice; if that’s the case, identical or very similar genetic constitutions (called genotypes) should be detected in plague victims from different time periods.
To investigate, Lisa Seifert of Ludwig Maximilian University of Munich and colleagues analyzed ancient DNA from 30 victims of the second plague pandemic excavated from two different burial sites in Germany: Manching-Pichl and Brandenburg. These remains were between 300 and 600 years old. One of the samples originated from a multiple inhumation of three male soldiers (pictured above) in Brandenburg dating back to the Thirty Years’ War, which lasted from 1618 to 1648.
Eight of the skeletons were positive for genetic material specific to Y. pestis. And despite a geographical distance of 500 kilometers (310 miles) and a time difference of 300 years, an identical Y. pestis genotype was detected in five human individuals. That means that at least one Y. pestis genotype persisted in Germany for three centuries during the second plague pandemic, and this was likely in addition to a continuous reintroduction of the plague bacterium from central Asia.
Furthermore, the genetic material found in these individuals was very similar to previously examined plague victims from other European countries, including remains from the U.K. dating back to the mid-1300s. The pathogen may have hidden in Europe for centuries in a reservoir host that’s still unknown.