Researchers Say Bacteria Responsible for Black Death During Middle Ages is Extinct

Posted on August 30, 2011

Flea Photo

Researchers say a flea that lives on rats was the culprit for the Black Death that killed many humans during the Middle Ages. The flea was carrying a strain of bacterium Yersinia pestis that the reseachers believe is now extinct. A different Y. pestis strain causes plague in humans today. The results of the research were published in the Proceedings of the National Academy of Sciences.

The researchers examined 100 skeletal remains of Black Death victims from the East Smithfield mass burial site in London. The researchers say these people died between 1348 and 1350. The researchers found a strain of Yersinia pestis in some of the victims, but it does not match the modern strains that cause plague today. The researchers also say, "Our data reveal that the Black Death in medieval Europe was caused by a variant of Y. pestis that may no longer exist."

Not everyone thinks a bacteria carried by rat fleas were the cause of the Black Death. The Guardian recently reported that Barney Sloane, author of The Black Death in London, believes the deadly disease spread form person to person. The author notes that mortality rates climbed during a severe winter during which the fleas would have perished. He also suspects the Black Death killed as many as two-thirds of the people living in London.

Photo: Image of flea/CDC/ World Health Organization

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