The plague has decimated Europe across the centuries, with waves of the disease resurging every few hundred years in pandemics—including the third pandemic of the plague, which began in the 19th century and is ongoing to this day.
The most famous wave of the plague, however, was the second—the Black Death, which killed 30 to 50 percent of the European population. And while it began in the 14th century, it resurged time and time again into the 18th century, leaving researchers with many questions: Where did these outbreaks begin? Why did it keep returning? And what happened to the plague in between resurgences?
Disease in hiding
Now, an international team led by the Max Planck Institute (MPI) for the Science of Human History in Jena, Germany may just have found some of those answers, because according to their research, the plague didn’t just die off—but hid somewhere on the European continent in between waves for hundreds of years.
According to the paper published in the journal eLife, the team extracted the plague’s DNA from the teeth of 10 of its victims, all of whom perished in the Great Plague of Marseille between 1720 and 1722. This plague outbreak is believed to be the last wave of medieval plague in Europe.
Marseille during the Great Plague of 1720.
However, it wasn’t an extraordinarily easy process. While the teeth preserved some of the plague’s DNA, each tooth only yielded fragments of the entire genome, leaving researchers to having to reconstruct the code. But it yielded surprising results.
“We faced a significant challenge in reconstructing these ancient genomes,” said computational analyst Alexander Herbig in a statement. “To our surprise, the 18th century plague seems to be a form that is no longer circulating, and it descends directly from the disease that entered Europe during the Black Death, several centuries earlier.”
Thus, it appears that the plague that swept through Marseille is a now-extinct form, whose source is highly uncertain. There are many theories as to how the plague resurged over the centuries, ranging from trading ships bringing in more disease-carrying rats to there being a sort of “Bing Bang” of plague—in which the disease slammed Europe once from Asia and remained on the continent ever after.
The most logical theory
The first theory seems to fit well; the three separate plague pandemics (the Justinian, the Black Death, and the modern one) have been shown genetically to come from separate variations of the disease imported from Asia. And Marseille itself was an enormous trade hub in the Mediterranean, so the first theory—that the later Great Plague of Marseille was the result of a ship bringing the plague around again—would fit logically.
However, the lineage of Marseille’s plague is close to that of the original outbreak in the 14th century—showing that the Black Death didn’t truly die off in Europe in between outbreaks. Rather, the evidence points to the disease lying in wait in some yet-unidentified pool for four hundred years.
“It’s a chilling thought that plague might have once been hiding right around the corner throughout Europe, living in a host which is not known to us yet,” said Johannes Krause, director of the Department of Archaeogenetics at the MPI in Jena. “Future work might help us to identify the mysterious host species, its range and the reason for its disappearance”.
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