- Researchers trace the roots of Europe's Black Death plague.
- The Black Death far from being just a more dangerous form of an already-occurring disease, was a newly evolved variant of a harmless bacteria.
- Even more surprising, the bacteria, of that era doesn't appear to be that much more virulent than the plague of today.
Plague germs teased from mediaeval cadavers in a London cemetery have shed light on why the bacterium that unleashed the Black Death was so lethal and spawned later waves of epidemics.
The DNA of Yersinia pestis shows, in evolutionary terms, a highly successful germ to which the population of 14th-century Europe had no immune defences, according to a study published Wednesday in the British journal Nature.
It also lays bare a pathogen that has undergone no major genetic change over six centuries.
"The Black Death was the first plague pandemic in human history," said Johannes Krause, lead researcher and a professor at the University of Tuebingen, Germany.
"Humans were (immunologically) naive and not adapted to this disease," he said in an email exchange.