The bacteria responsible for the Black Death that killed a third of Europe’s population from 1347 to 1351 has changed little since then as health and hygiene advances held it in check, scientists said.
Researchers extracted DNA from the teeth of four skeletons exhumed from a cemetery near the Tower of London to reconstruct the Yersinia pestis genome, according to a report yesterday in the journal Nature. The study determined the germ is still circulating yet probably didn’t cause earlier plagues in Rome and Greece, suggesting the European outbreak was the first to spread the bacteria worldwide, the researchers said.
“We do not see a single position in the ancient genome that cannot be found in modern Y. pestis in the same state,” said researcher Johannes Kraus, a professor in the departments of archeological sciences and human genetics at the University of Tubingen in Tubingen, Germany.
Modern antibiotics can effectively kill the ancient bacteria, said Hendrik Poinar, a researcher at the departments of ancient DNA, biology and infectious disease at McMaster University in Hamilton, Ontario.
The virulence of the outbreak may have occurred because there were other infections circulating at the time, there was a dramatic change in the weather and a less hearty population, Poinar said yesterday during a televised news conference. “There is no smoking gun,” he said.
Kraus said later generations also adapted to the outbreak of the bacteria, helping minimize its deadly effects.
At first, “people basically don’t know what pathogen it is, what kind of disease it is, they don’t know how to treat it, they don’t know what to do,” he said. “Later on, people had developed containment, first aid, how to treat patients with the symptoms. That could all play a big role to lower virulence at later outbreaks.”
Researchers used tools and technology recently developed to study Neanderthals to enrich the material they extracted from the teeth to ensure they had authentic ancient bacteria. They analyzed about 99 percent of the genome, Kraus said.
More work is needed to examine small variations to ensure a different layout wouldn’t make it more deadly, according to the researchers.