Black Death Pathogen Likely Extinct

The so-called "Black Death," a plague that ravaged Europe between the years of 1347 and 1351, was likely caused by a now-extinct version of the Yersinia pestis bacterium, according to results of a study published online on August 29, 2011 in PNAS. Dr. Hendrik Poinar, from McMaster University in Canada, and colleagues made this determination after analyzing the DNA of 109 human skeletal remains excavated at the East Smithfield mass burial site in London, England. The researchers also studied DNA from the remains of 10 humans unearthed at St. Nicholas Shambles, a site pre-dating the Black Death medieval plague. Individuals buried at East Smithfield harbored Y. pestis genes, which the authors sequenced to form among the oldest and longest genetic assemblages from an ancient pathogen. The genetic sequence differs from the sequences of other known versions of Y. pestis, the authors found, suggesting that the pathogen responsible for the Black Death is likely extinct. Because modern plague continues to affect an estimated 2,000 people per year worldwide, the authors suggest that earlier forms of the disease may yield clues about the pathogen's evolutionary history and possibly reveal how it caused such widespread devastation during the Black Death period. [Press release] [PNAS abstract]