German scientists from Max Planck Institute (MPI) have reconstructed complete pathogen genomes from victims of the Great Plague of Marseille, which took place from 1720 to 1722. This is a part of their way to further understanding Black Death.

"It's a chilling thought that plague might have once been hiding right around the corner throughout Europe, living in a host which is not known to us yet," explained Johannes Krause, director of the department of archaeogenetics at the MPI.

The scientists used the teeth from 101 victims that were found in six different plague pits. These sites include three in Russia, one in Armenia, one in Poland, and one in Estonia. From these teeth, the scientists were able to get hold of tiny fragments of preserved DNA. It showed that the bacterium, Yersinia pestis, has afflicted humans as long ago as about 2800 BC. That is more than 3,000 years earlier than the oldest previous evidence of plague.

"To our surprise, the 18th century plague seems to be a form that is no longer circulating, and it descends directly from the disease that entered Europe during the Black Death, several centuries earlier," explained computational analyst Alexander Herbig.

Great Plague of Marseille is believed to be the last outbreak of medieval plague in Europe. It is considered to be the most historical pandemic. In a span of five years, the Black Death has resulted to the end of 30-50 percent of the European population.

But, apparently, it was not the end for the pathogen. Plague resurged throughout Europe leading to continued high mortality and social unrest over the next three centuries.

"Our results suggest that the disease was hiding somewhere in Europe for several hundred years," said lead author Kirsten Bos in a paper that appeared in the journal eLife.

"Future work might help us to identify the mysterious host species, its range and the reason for its disappearance," Krause added.

"It seems to have started impacting human populations over large geographical scales way earlier than we thought," said evolutionary geneticist Eske Willerslev of the University of Copenhagen and University of Cambridge.

Yersinia pestis is behind two of humankind's deadliest pandemics: the 6th century Justinian Plague, named for the Byzantine emperor who was sickened but survived, and the 14th century Black Death.