The Justinianic Plague of the sixth to eighth centuries was caused by the bacterium Yersinia pestis, scientists have confirmed.
This pandemic, named after the Byzantine emperor Justinian I, killed more than 100 million people. Some historians have even suggested it contributed to the decline of the Roman Empire.
From the several pandemics generally called 'pestilences' three are historically recognized as due to plague, but only for the third pandemic of the 19th-21st centuries AD there were microbiological evidences that the causing agent was the bacterium Yersinia pestis.
"For a long time scholars from different disciplines have intensively discussed about the actual etiological agents of the past pandemics. Only ancient DNA analyses carried out on skeletal remains of plague victims could finally conclude the debate", said Dr. Barbara Bramanti of the Palaeogenetics Group at the Institute of Anthropology at Johannes Gutenberg University Mainz (JGU).
About two years ago, she headed the international team that demonstrated beyond any doubt that Y. pestis also caused the second pandemic of the 14th-17th centuries including the Black Death, the infamous epidemic that ravaged Europe from 1346-1351.
Bramanti and her Mainz colleague Stephanie Hansch now cooperated with the University of Munich, the German Bundeswehr, and international scholars to solve the debate as to whether Y. pestis caused the so-called Justinianic Plague of the 6th-8th centuries AD.
The results of ancient DNA analyses carried out on the early medieval cemetery of Aschheim in Bavaria confirmed unambiguously that Y. pestis was indeed the causing agent of the first pandemic, in contrast to what has been postulated by other scientists recently.
This revolutionary result is supported by the analysis of the genotype of the ancient strain, which provide information about the phylogeny, and the place of origin of this plague. As for the second and third pandemic, the original sources of the plague bacillus were in Asia.
"It remains questionable whether at the time of the Byzantine Emperor Justinian only one strain or more were disseminated in Europe, as it was at the time of the Black Death," suggested Bramanti and Hansch.
To further investigate this and other open questions about the modalities and route of transmission of the medieval plagues, Bramanti has recently obtained an ERC Advanced Grant for the project "The medieval plagues: ecology, transmission modalities and routes of the infection" (MedPlag) and will move to the Center for Ecological and Evolutionary Synthesis (CEES) at the University of Oslo in Norway.
The CEES, chaired by Nils Chr. Stenseth, has an outstanding and rewarded record of excellence in the research on infectious diseases and in particular on Y. pestis.
The results of their study were published last week in PloS Pathogens.