Researchers from Florida Atlantic University and the University of South Florida have provided the first direct genomic evidence linking Yersinia pestis, the bacterium responsible for plague, to the Plague of Justinian. This pandemic, which began in AD 541, is recognized as the world’s first recorded pandemic and had significant effects on the Byzantine Empire.
The team found traces of Y. pestis in a mass grave at Jerash, Jordan, near where historical accounts say the outbreak began. This discovery fills a gap in scientific understanding about what caused the widespread deaths during that period.
“For centuries, we’ve relied on written accounts describing a devastating disease but lacked any hard biological evidence of plague’s presence. Our findings provide the missing piece of that puzzle, offering the first direct genetic window into how this pandemic unfolded at the heart of the empire,” said Rays H. Y. Jiang, Ph.D., lead PI of the studies and associate professor with the USF College of Public Health.
Previous attempts to find evidence for Y. pestis within core areas affected by the Justinian Plague had not succeeded; earlier samples came from much farther away in western Europe.
“Using targeted ancient DNA techniques, we successfully recovered and sequenced genetic material from eight human teeth excavated from burial chambers beneath the former Roman hippodrome in Jerash, a city just 200 miles from ancient Pelusium,” said Greg O’Corry-Crowe, Ph.D., co-author and a research professor at FAU Harbor Branch Oceanographic Institute and a National Geographic Explorer.
Analysis showed that those buried carried nearly identical strains of Y. pestis between AD 550–660. Researchers say this suggests a rapid outbreak consistent with historic descriptions.
“The Jerash site offers a rare glimpse of how ancient societies responded to public health disaster,” said Jiang. “Jerash was one of the key cities of the Eastern Roman Empire, a documented trade hub with magnificent structures. That a venue once built for entertainment and civic pride became a mass cemetery in a time of emergency shows how urban centers were very likely overwhelmed.”
A related study analyzed hundreds of ancient and modern genomes for Y. pestis and concluded that major plague pandemics did not all descend from one strain but emerged independently over time due to repeated spillovers from animal reservoirs rather than continuous human-to-human transmission.
“This research was both scientifically compelling and personally resonant. It offered an extraordinary opportunity to delve into the study of human history through the lens of ancient DNA at a time when we ourselves were living through a global pandemic,” said O’Corry-Crowe. “Equally profound was the experience of working with ancient human remains – individuals who lived, suffered and died centuries ago – and using modern science to help recover and share their stories. It’s a humbling reminder of our shared humanity across time and a moving testament to the power of science to give voice to those long silent.”
The researchers note that although rare today, cases still occur globally; recent examples include fatalities in Arizona and California due to pneumonic plague.
“We’ve been wrestling with plague for a few thousand years and people still die from it today,” said Jiang. “Like COVID, it continues to evolve, and containment measures evidently can’t get rid of it. We have to be careful, but the threat will never go away.”
The team plans further work at Venice’s Lazaretto Vecchio quarantine island—home to thousands buried during later outbreaks—to study links between public health responses and pathogen evolution.
