The great waves of plague that twice devastated Europe and changed the course of history had their origins in China, a team of medical geneticists reported Sunday, as did a third plague outbreak that struck less harmfully in the 19th century.
...The three plague waves have now been tied together in common family tree by a team of medical geneticists led by Mark Achtman of University College Cork in Ireland. By looking at genetic variations in living strains of Yersinia pestis, Dr. Achtman’s team has reconstructed a family tree of the bacterium. By counting the number of genetic changes, which clock up at a generally steady rate, they have dated the branch points of the tree, which enables the major branches to be correlated with historical events.
In the issue of Nature Genetics published online Sunday, they conclude that all three of the great waves of plague originated from China, where the root of their tree is situated. Plague would have reached Europe across the Silk Road, they say. An epidemic of plague that reached East Africa was probably spread by the voyages of the Chinese admiral Zheng He who led a fleet of 300 ships to Africa in 1409.
“What’s exciting is that we are able to reconstruct the historical routes of bacterial disease over centuries,” Dr. Achtman said.