A deadly pandemic with mysterious origins: It may sound like a modern headline, but scientists have spent centuries debating the source of thethat devastated the medieval world.
Not anymore, according to researchers who say they have pinpointed the origin of the plague in a region of Kyrgyzstan, after analyzing DNA from remains at an ancient burial site.
“We managed to put an end to all these centuries-old controversies about the origins of the Black Death,” said Philip Slavin, a historian and part of the team whose work was published Wednesday in the journal Nature.
The Black Death was the initial wave of a nearly 500-year pandemic. In just eight years, from 1346 to 1353, it killed up to 60% of the population of Europe, the Middle East and Africa, according to estimates.
Ancient DNA traces the origin of the Black Death https://t.co/NNd656FmhG
— nature (@Nature) June 15, 2022
Slavin, an associate professor at the University of Stirling in Scotland who “has always been fascinated with the Black Death,” found an intriguing clue in an 1890 paper describing an ancient burial site in what is now northern Kyrgyzstan.
He reported an increase in burials in 1338-39 and that several tombstones described people who had “died of pestilence”.
“When you have one or two years with excess mortality, it means something strange was going on there,” Slavin told reporters.
“But it wasn’t just any year: 1338 and 1339 were just seven or eight years before the Black Death,” he said.
It was a clue, but nothing more without determining what killed the people on the site.
For that, Slavin partnered with specialists who examine ancient DNA.
They extracted DNA from the teeth of seven people buried at the site, explained Maria Spyrou, a researcher at the University of Tübingen and author of the study.
Because the teeth contain many blood vessels, they give researchers “high chances of detecting blood-borne pathogens that may have caused the death of individuals,” Spyrou told AFP.
Once extracted and sequenced, the DNA was compared to a database of thousands of microbial genomes.
“One of the hits we were able to get … was a hit for Yersinia pestis,” more commonly known as plague, Spyrou said.
The DNA also showed “characteristic patterns of damage,” he added, showing that “what we were treating was an infection that the ancient individual was carrying at the time of death.”
The start of the Black Death has been linked to an event called the “Big Bang”, when existing strains of the plague, which is transmitted by rodent fleas, suddenly diversified.
Scientists thought it might have happened as early as the 10th century, but were unable to determine a date.
The research team painstakingly reconstructed the Y. pestis genome from their samples and found that the strain at the burial site predated diversification.
And it was also found that rodents living in the region now carried the same ancient strain, helping the team conclude that the “Big Bang” must have occurred somewhere in the area in a short period before the Black Death.
The research has some unavoidable limitations, including a small sample size, according to Michael Knapp, an associate professor at New Zealand’s University of Otago who was not involved in the study.
“Data from many more people, times and regions … would really help clarify what the data presented here really means,” Knapp said.
But he acknowledged that finding additional samples could be difficult, and praised the research as “really valuable.”
Sally Wasef, a palaeogeneticist at Queensland University of Technology, said the work offers hope of unraveling other ancient scientific mysteries.
“The study has shown how the robust recovery of ancient microbial DNA could help reveal evidence to resolve long-running debates,” he told AFP.
According to the World Health Organization, between 2010 and 2015 a total of 3,248 cases were reported worldwide, resulting in 584 deaths. The Democratic Republic of the Congo, Madagascar and Peru were the most affected countries.
Plague was first introduced to the US in 1900 from steamships carrying infected rats. The last urban outbreak of rat-associated plague in the US was in Los Angeles between 1924 and 1925.
According to the US Centers for Disease Control and Prevention, people usually get bubonic or septicemic plague after being bitten by a flea that carries the bacteria. Humans can also get the disease when they handle an animal that is infected.
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