Source of Black Death found in London graveyard

An extinct version of the Yersinia pestis bacterium that is believed to be responsible for causing the Black Death was recently discovered by a team of evolutionary geneticists working in a 14th century London graveyard.

The team, led by Hendrik Poinar from McMaster’s Michael G. DeGroote Institute for Infectious Disease Research, used high-throughput DNA sequencing and a novel way of DNA enrichment to make the find, according to

Between 1347 and 1351, the plague is thought to have killed 30 to 50 million people living in Europe. Scientists have never fully understood what mechanism caused the plague, whose modern equivalent kills approximately 2,000 people around the world every year.

“One-third of the population of Europe died and the question in the beginning was, 'What was the bug that started it?'" Poinar said, reports. "The Black Death is arguably one of the most dramatic examples ever of emerging or re-emerging disease. By studying the origin of this disease it may yield information concerning the organism's evolutionary history as a human pathogen.”

The scientists say their study, which was published in the Proceedings of the National Academy of Science, indicates that the plague has emerged in three major pandemics, the first of which is the Plague of Justinian in 541 AD. The 20th century plague is the most recent.

The team examined the skeletons of 109 plague victims who were buried at East Smithfield, London, in 1349. After analyzing DNA samples found at the site, they discovered that the bodies contained Y. pestis genes.

According to their preliminary findings, the team said that the pathogen that caused the Black Death is a now extinct variant that was extremely virulent in 1348.

“It’s probably exceptionally important to find out what made this bug so deadly in the past,” Dr. Poinar said, the New York Times reports.