Cause Behind Justinianic Plague Uncovered with the Help of Ancient DNA

Long ago, the plague ravaged Europe. People died by the millions as they succumbed to the sickness; bodies were loaded into mass graves as the survivors attempted to eke out a living. Now, researchers have examined ancient DNA from the remains of plague victims from the 6^th century AD to learn a bit more about the phylogeny and the origin of the pandemic that hit the Byzantine Empire.

There are several pandemics that are generally called "pestilences" throughout our history. Three in particular are historically recognized as the plague. Yet researchers have often wondered whether during the Justinianic Plague in the 6^th to 8^th centuries, the causing agent was the bacterium Yersinia pestis. This rod-shaped bacterium can infect both humans and other animals, and was responsible for the Black Death. This infamous epidemic ravaged Europe from 1346 to 1351, killing infected individuals in a matter of days.

"For a long time scholars from different disciplines have intensively discussed the actual etiological agents of the past pandemics," said Barbara Bramanti of the Palaeogenetics Group at the Johannes Gutenberg University Mainz in a press release. "Only ancient DNA analysis carried out on skeletal remains of plague victims could finally conclude the debate."

The Justinianic Plague, also known as the Plague of Justinian, wiped out roughly one third of the Byzantine Empire's population. It caused major military and financial difficulties, and had a major effect on the future course of European history. The social and cultural impact this plague had is comparable to that of the Black Death.

In order to find out whether or not Y. pestis was responsible, the researchers carried out DNA analyses on remains in the early medieval cemetery of Aschheim in Bavaria. More specifically, they analyzed the genotype of this ancient strain of bacteria; this provided information about the phylogeny and the place of origin of this plague. After examining the remains, the researchers were able to confirm that Y. pestis was indeed the cause of the first pandemic. Yet that doesn't mean that the researchers have learned all that they can about the plague.

"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," said Bramanti in a news release.

In order to answer this question, the researchers plan to continue examining ancient remains. They hope that they will be able to find out the route of transmission of the medieval plagues, and learn a bit more about these historic incidents.

The findings are published in the journal PLOS Pathogens.