Researchers trace the roots of Europe's Black Death plague

By Elizabeth Weise, USA TODAY
October 13, 2011

The Black Death of the medieval era, far from being just a more dangerous form of an already-occurring disease, was a newly evolved variant of a harmless bacteria that quickly began its death march across the globe.

That's the finding of researchers who have sequenced the genome, or genetic blueprint, of plague bacteria and found that the strain arose no more than 140 years before the bubonic plague's start in 1347.

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