This new information could help predict future strains of the plague.

“We’re into the basic understanding of the tempo and mode of the Justinian strain,” Poinar says. “It’s kind of a boom-bust situation. It erupted, killed a lot of people and then went extinct.”

While the Black Death continues to pop up in isolated incidences across the world, the Justinian plague never appeared again and Poinar is interested in what stopped it. He thinks one of the reasons the plague may have disappeared in Europe was due to changing climates that affected the ecology of the species of rats that typically carry it and transmit it to humans through fleas. He says that broader knowledge of the kind of weather suitable to these rats could help pinpoint potential plague outbreaks in the future.

“It would be good to know that rodents in certain areas could create pandemic plague,” he says, adding that the information could help alert local authorities of the potential danger.

Poinar says the chances of another pandemic like those that levelled Europe in the past is unlikely, noting improved sanitation over the years. But the plague usually lies dormant for centuries, and still occasionally appears in parts of Africa, China and the Middle East.