A study of 1,500 year old skeletons has raised new concerns about the threat of the plague to humanity, researchers said last night.
An international team has been studying DNA found in the teeth of two skeletons of people buried in a Bavarian town in the sixth century.
They were victims of the Plague of Justinian, which put an end to hopes of restoring the Roman Empire.
The study, reported in The Lancet Infectious Diseases, confirms that the bacteria responsible for the Justinian plague were an evolutionary "dead end."
The mediaeval Black Death was also caused by the plague bacteria, Yersinia pestis, but not a strain that evolved from the sixth century plague bacteria.
The researchers say this has alarming implications – meaning the bacteria can suddenly evolve to achieve the ability to cause a plague epidemic and then die out just as quickly.
Researcher Dave Wagner, of Northern Arizona University, USA, said: "We know the bacterium Y. pestis has jumped from rodents into humans throughout history and rodent reservoirs of plague still exist today in many parts of the world. If the Justinian plague could erupt in the human population, cause a massive pandemic, and then die out, it suggest it could happen again.
"Fortunately we now have antibiotics that could be used to effectively treat plague, which lessens the chances of another large scale human pandemic."
Fellow researcher Hendrik Poinar, of McMaster University, Ontario, Canada, said: "The research is both fascinating and perplexing, it generates new questions which need to be explored, for example why did this pandemic, which killed somewhere between 50 and 100 million people die out?"
The Lancet Infectious Diseases 27 January 2014
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