Plague origins may have emerged centuries before outbreaks, study suggests

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In the largest DNA analysis of its kind, scientists believe that historic plague outbreaks such as the Black Death were not caused by newly evolved strains of bacteria, what may have appeared centuries ago their occurrence.

Yersinia pestis, Yersinia pestis, is believed to have first appeared in the human body. 5000 years agoThrough animals and trade routes, Yersinia pestis has spread around the world many times. study It was published Thursday in the journal Communications Biology.

It caused the first plague epidemic from the 6th to the 8th century and the second from the 14th to the 19th century. The latter pandemic is believed to have started with the outbreak of the Black Death in the Middle Ages, estimated to have killed more than half of Europe’s population. This bacterium also caused his third plague outbreak from the 19th century to his 20th century.

By collecting the genome sequences of 601 Yersinia pestis, including current and ancient strains, researchers in Canada and Australia were able to calculate when the bacterial strain likely emerged as a threat. . They classified different strains of Y. pestis and analyzed each strain population separately.

The strain responsible for the Black Death, thought to have begun in 1346, was newly estimated to have diverged from an ancestral strain between 1214 and 1315.

a strain of Yersinia pestis associated with the first plague Before the pandemic Plague of Justinian, which began in 541. However, the researchers estimated that the strain was already present between 272 and 465, or almost 270 years before the outbreak.

Study co-author and evolutionary geneticist Hendrik Poiner, director of the Center for Ancient DNA at McMaster University in Canada, told CNN in an email Thursday.

He added that germs would emerge, cause small epidemics, and “for reasons we don’t quite understand” such as famine and war, “it will take off.”

The authors of this study found that the bacterial strain of the third plague epidemic, evaluated separately, diverged from an ancestral strain between 1806 and 1901 and became very popular in southern China between 1772 and 1880. localized plague cases began to appear in Hong Kong from 1894 to 1901.

The study also found evidence that supports recent academic research. This suggests that the third and his second plague pandemic were not mutually exclusive events, and that the third was partly a continuation or tail of his second pandemic. Despite the pandemic having its own diverse genetic lineage that evolved differently, the third was directly derived from his 14th-century strain that caused his second.

Poinard called this discovery an important one. “Given that most of the history of this bacterium was a Eurocentric view, the plague seems to have disappeared from Europe in the 18th century (century), but continued to rage in the Ottoman Empire. Middle East and possibly North Africa.”

However, even with the vast array of Y. pestis, researchers were unable to pinpoint the route of plague’s global spread.

Many genetic samples come from Europe. For example, with the emergence of bacteria in Africa, 90% of modern plague cases occur on the continent, but this region has no ancient sequences and only 1.5% of total genome samples. So far, the emergence of Yersinia pestis in Africa.

Also, historical evidence for a second plague epidemic that helps deduce the geographic origin of the plague is The third is the earliest documented evidence of a pandemic in Europe from the Black Death of 1346, say the study authors. Researchers estimate that the second pandemic originated in Russia.

Ah study Published in Nature in June using DNA analysis Finding Yersinia pestis in Three People Who Supposedly Died in 1338 in present-day Kyrgyzstan in Central Asia. He provided evidence that the Black Death originated from a strain originating near Lake Issyk-Kul in Kyrgyzstan in the early 14th century.

A new study concludes that older DNA will be needed to improve current estimates of the early events of a second pandemic.

In an email, Poinar described strains from Kyrgyzstan as “really fascinating,” but said, “We’re not at the root yet. I think.”

He and other authors say that the only way to accurately estimate the evolution of plague strains is “using well-dated sequences, such as those from the skeletal remains of Lake Issyk-Kul.”