A deadly pandemic with mysterious origins: It may seem like a modern headline, but scientists have spent centuries debating the source of the virus.that devastated the medieval world.
Not anymore, according to researchers who say they have identified the source of the plague in a region of Kyrgyzstan, after analyzing DNA from remains in an ancient cemetery.
“We’ve managed to end all those 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-old 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 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 by the Black Death,” found an intriguing clue in an 1890s work depicting an ancient cemetery in what is now northern Kyrgyzstan.
He reported an increase in burials in 1338-39 and that several tombstones depicted people who “died of pestilence”.
“When you have a year or two with excess mortality, it means something funny was happening 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 at the scene.
To do this, Slavin teamed up with experts 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 Tuebingen and author of the study.
Because teeth contain many blood vessels, they give researchers “a high chance of detecting blood-borne pathogens that may have caused the individuals’ death,” Spyrou told AFP.
Once extracted and sequenced, the DNA was compared against a database of thousands of microbial genomes.
“One of the hits we got… was a hit for Yersinia pestis,” more commonly known as the plague, Spyrou said.
The DNA also exhibited “characteristic damage patterns,” she added, showing that “what we were dealing with was an infection that the former individual was carrying at the time of his death.”
The onset of the Black Death has been linked to an event called the “Big Bang”, when existing strains of the plague, which is carried by fleas on rodents, suddenly diversified.
Scientists thought it could have happened as early as the 10th century, but have been unable to pinpoint a date.
The research team painstakingly reconstructed the genome of Y. pestis from their samples and found that the strain at the burial site predated diversification.
And rodents living in the region have now also been found carrying the same ancient strain, helping the team conclude that the “Big Bang” must have happened somewhere in the area in a small window before the Black Death.
The research has some unavoidable limitations, including a small sample size, according to Michael Knapp, an associate professor at the University of Otago in New Zealand who was not involved in the study.
“Data from a lot more individuals, times and regions… would really help to clarify what the data presented here really means,” Knapp said.
But he acknowledged that it can be difficult to find additional samples and praised the research as “really valuable.”
Sally Wasef, a paleogeneticist at Queensland University of Technology, said the work offers hope for unraveling other ancient scientific mysteries.
“The study showed how robust recovery of ancient microbial DNA can help uncover evidence to resolve long-lasting debates,” she told AFP.
According to the World Health Organization, a total of 3,248 cases were reported worldwide between 2010 and 2015, resulting in 584 deaths. The Democratic Republic of Congo, Madagascar and Peru were the most affected countries.
The 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 occurred in Los Angeles between 1924 and 1925.
According to the US Centers for Disease Control and Prevention, people commonly contract bubonic or septicemic plague after being bitten by a flea that carries the bacteria. Humans can also contract the disease from handling an infected animal.
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