Bacterial genes discovered in skeletons dating to the period from the 14th to the 17th century indicate that the pathogen causing plague may have survived in Europe for hundreds of years, according to a report in the journal PLOS ONE.
This suggests plague could have broken out without having to be brought in anew from other continents, as has been commonly believed. The bacterium Yersinia pestis was apparently able to survive on its own in Europe, perhaps in blood-sucking insects.
Plague continues to kill people, mainly in Africa, although antibiotics are an effective remedy. World Health Organization data shows nearly 800 cases in 2013 with 126 deaths.
"In the tooth pulp of the skeletons investigated, we found DNA characteristic of the pathogen that caused plague and investigated its molecular fingerprint," Holger Scholz of the German Army's Microbiology Institute in Munich said.
"We discovered that it was basically identical in them all," Scholz said of the skeletons found in both Munich in the south of Germany and Brandenburg near Berlin in the north-east.
Scholz investigated 30 skeletons in cooperation with researchers at Munich's Ludwig Maximilian University and the State Collection for Anthropology and Palaeoanatomy.
The genetic material of six of them could be used for analysis, allowing the team to chart the period from the mid-14th to the late 17th century. Data from other European skeletons were also compared, allowing a virtually identical genetic fingerprint of the persistent strain to be established.
At the time, it was generally believed that merchants, seafarers or others arriving from Asia, the Middle East or Africa brought each new bout of plague.
The host in which the European bacteria survived is not known. "Perhaps it was in lice, but we were unable to demonstrate this," Scholz said.