An international team of scientists tracing the origins of two of the world’s most devastating plagues says strains of the same plague caused the pandemics hundreds of years ago. They warn that new strains could trigger future outbreaks.
The so-called Plague of Justinian, the first one known to historians, struck in the sixth century. The pandemic originated in China and killed between 30 and 50 million people as it spread across Asia, northern Africa, Arabia and Europe between 1347 and 1354. Experts believe that plague, caused by a bacterium carried by rodents, contributed to the fall of the Roman Empire.
Eight hundred years later, according to researchers, the Black Death killed an estimated 75 million to 200 million people in Europe and North Africa. Expert say this plague, which also originated in Asia, was hardier, resurfacing in the 1800s. The Black Death was caused by a different strain of the same bacterium that caused the Justinian Plague.
Experts stitched together the genetic findings of the two pandemics by unearthing and analyzing DNA from the remains of individuals who died during the Justinian and Black Plagues.
Hendrik Poinar, an expert on ancient DNA at McMaster University in Ontario, Canada, says the bacteria that causes the plague are carried by rodents. Poinar said that pockets of the Black Death remain among people living in both Madagascar and the American Southwest, a sign of the bacterium’s resilience.
“The plague we have today in squirrels or prairie dogs in the American Southwest, those are all descendants of the Black Death," he said. "So, the Black Death is much more successful, if you will, in disseminating out across the globe whereas Justinian came and basically burned itself out.”
As with any other infectious disease, Poinar says it is important to keep an eye on plague outbreaks to make sure they do not become pandemics. Poinar notes, however, that cities today are much cleaner than they were centuries ago, something he says would reduce the likelihood of a reemergence of a plague pandemic.
"Thirteen-forty-eight London was probably not a very clean place," he said. "And so in today's day and age, we have antibiotics which would be successful against these epidemics. And certainly our cities are in much better states and can handle these sorts of onslaughts."
Poinar says it is important to watch areas where there are pockets of plague, especially since global warming can draw rodents looking for food and water to population centers.
An article by Canadian, Australian and U.S. researchers on plague origins is published in the journal The Lancet Infectious Disease.