New research into the bubonic plague behind the deadliest pandemics in human history
(ORDO NEWS) — To better understand the origins and spread of bubonic plague in ancient and modern times, researchers from McMaster University, the University of Sydney and the University of Melbourne conducted a multi-year detailed study of hundreds of modern and ancient genome sequences of the plague-causing bacterium, the plague bacillus.
An exhaustive answer about the origin of the Black Death has not yet been obtained, but the largest database of plague bacillus genomes for 5000 years has been created.
In an effort to better understand the origin and spread of bubonic plague in ancient and modern times, scientists from McMaster University, the University of Sydney and the University of Melbourne conducted a detailed study of hundreds of modern and ancient genome sequences of the plague bacterium Yersinia pestis.
Despite tremendous advances in technology and DNA analysis, the origin, evolution, and spread of the plague remains difficult to pinpoint.
Plague is the cause of two of the largest and deadliest pandemics in human history. However, why they began and ended, why in some cases the epidemic passed quickly, while in others it lasted for years, is still not clear.
The study includes an analysis of more than 600 genomic sequences from around the world, spanning from the first appearance of the plague in humans 5,000 years ago, the Plague of Justinian, the medieval Black Death, and the current pandemic that began in the early 20th century. Although this pandemic is not as deadly as previous ones, it still provokes serious outbreaks.
Plague pits in East Smithfield used for mass graves in 1348 and 1349
Plague pits in East Smithfield used for mass graves in 1348 and 1349
Museum of London Archeology
“The plague was the largest and deadliest pandemic in human history. It constantly flared up for hundreds of years and died out in some places, but persisted in others. And we still don’t know why it killed so many people,” says co-author Hendrik Poinar, director of the Center for Ancient DNA at McMaster University.
What makes the plague bacillus unique?
A team of scientists studied the genomes of Y. pestis strains in various regions of the world and at various times. Scientists have shown that Y. pestis has an unstable molecular clock.
This makes it particularly difficult to measure the rate at which mutations accumulate in the genome over time.
The accumulation of mutations usually determines the time of the appearance of the first strain, but in the case of the plague bacillus, this is extremely difficult to do.
Y. pestis develops so slowly that it is almost impossible to determine exactly when and where the first strain originated.
Humans and rodents carried the pathogen around the world. The plague wand spread along with merchant ships and caravans. But the bacterium moved faster than its genome changed.
The genomic sequences found in Spain, England, Italy and Turkey, despite being separated by years, are identical, which creates great problems for determining the route of transmission.
To solve this problem, the researchers developed a new method to distinguish between specific populations of Y. pestis.
This has allowed five populations of the plague bacillus to be identified and dated throughout history, including the most famous ancient pandemic lineages that emerged decades or even centuries before the historically documented pandemic in Europe, the Black Death.
It turns out that the finished bacterium has been waiting for its chance for centuries, and in the end it got it.
Historical, environmental, social and cultural contexts are equally important for correctly reconstructing past and present pandemics and predicting future outbreaks.
Scientists emphasize that genetic data alone is not enough to reconstruct the timing and spread of plague pandemics.
Such interdisciplinary collaboration is important both for research related to past pandemics and for the study of current outbreaks such as COVID-19.
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