Black Death bacteria may be extinct - Study

By Dr. Ananya Mandal, MDAug 30 2011

The bacteria that caused the Black Death or plague, which wiped out millions in mid-14th century Europe, may be extinct, according to a new study. The Black Death claimed the lives of one-third of Europeans in just five years from 1348 to 1353. Until recently, it was not certain whether the bacterium Yersinia pestis - known to cause the plague today - was responsible for that most deadly outbreak of disease ever. Now, the University of Tübingen's Institute of Scientific Archaeology and McMaster University in Canada have been able to confirm that Yersinia pestis was behind the great plague.

German and Canadian researchers examined more than 100 samples taken from bodies buried in London during that time. “The Black Death was caused by the bacterium Yersinia pestis — the one responsible for current plague outbreaks. This settles the controversy surrounding the causative agent. Although we cannot rule out, at this stage, that there was another co-circulating strain,” said study author Hendrik Poinar, a biological anthropologist at McMaster University in Ontario. He explained that the genetic sequence of the bacteria in the London bodies differed from the sequences of modern versions of Y. pestis, suggesting that the strain responsible for the Black Death is likely extinct.

The bubonic plague, which is the infection that spread during the Black Death pandemic, persists in the world today. Small outbreaks emerge in the southwestern United States every few years, and in 2009, the Chinese government quarantined a town in Qinghai province for ten days after an outbreak there.

But differences between plagues has led some to speculate that the Black Death was the result of an agent other than Y. pestis bacteria, with some even saying it more closely resembled infections of the Ebola virus, based on historical descriptions.

The researchers found that people who died during the Black Death had genes of Y. pestis, while the bodies of people who had died earlier nearby lacked these genes.

“I think it's an elegant study and it's very intriguing,” Dr. Howard Markel, a medical historian at the University of Michigan, said of the study. “It's really neat, really hard to do, but there were millions who succumbed to the black plague.” The 109 bodies examined in the new study represent “a small slice,” he said.

Poinar agreed that the new study cannot account for all plague infections. “The follow-up is clearly to get more plague genomes, from other outbreaks, to compare them across both space and time,” he said.

But Markel expressed some skepticism at the ability of such research to curb present epidemics entirely. “We never really conquer germs, we just wrestle them to a draw at best,” he said.

The results of the research are published in the Proceedings of the National Academy of Sciences.