Recent collaborative genetic study by a team of researchers from Germany, Ireland, China, France, England and the United States confirm that numerous European plagues, including the Black Death of the 14th Century, had a common origin in China.
“Plague” specifically refers to an infectious disease caused by the enterobacteria Yersinia pestisi. It is primarily carried by rodents and transmitted to humans via species-specific flea vectors. Untreated infections can be fatal. Historically, epidemic expansions of the plague have resulted in several waves of pandemics.
Europe was struck by the Justinian’s plaque between 541 and 767, followed by the Black Death in 1346 that lasted throughout the 18th century. The most recent outbreak was the Great Plague of London between 1665 and 1666.
DNA and protein analysis from mass burial grounds and plague pits across different countries allowed scientists to both confirm the cause of the plagues and their routes of travel. Identification of Y. pestisi as the definite cause of the Black Plague settled the ongoing debate over its origins.
Y. pestisi can be subdivided into several strains based on the ability to ferment particular sugars and to reduce nitrate. Researchers differentiated between two strains of the bacteria as the cause of the Black Death, implying that two different sources of Y. pestisi must have invaded Europe via different routes.
Identical strains found in both Hereford, England and southern France suggests that one of the two strains arrived at England after spreading across France. Researchers infer that the other strain, found in Bergen op Zoom, came from Norway.
Prior to the Black Death, the Justinian plague of the 6th century killed over half the European population. The third wave of plague following the Black Death in 1894, originated in Yunnan province of China, which then spread to various areas around the world through the Hong Kong seaport.
Researchers have genetically linked the three waves of plagues, using constant rate genetic changes to date branches of the family tree of the bacterium and correlating historical events with major branches.
Tracing back, researchers conclude that all three plagues originated from China, and most likely reached Europe across the Silk Road, and East Africa from Zheng He’s expeditions in 1409. The commonness of many species of rodents — carriers of Y. pestisi — in China renders this conclusion highly probable.
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