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75 ancient genomes show the plague never really left for 400 years

Qurexa Editorial Team22 September 20267 min read 0 0
75 ancient genomes show the plague never really left for 400 years

What happened

Scientists have read the DNA of the bacterium that caused the Black Death, taken from people who died centuries ago, and pieced together where it went next. The answer is that it did not go away. It kept coming back, again and again, for more than 400 years. The study was led by researchers at the University of Tartu in Estonia. It was published in the Proceedings of the National Academy of Sciences and reported on 20 September 2026. The team reconstructed 26 new genomes of Yersinia pestis, the bacterium behind plague. These came from 11 archaeological sites across Estonia, Russia, England, the Netherlands and Switzerland. They then combined these with 64 genomes published by other researchers. Altogether that gave them 75 plague genomes spanning the 14th to the 18th centuries. The Black Death itself swept Europe between 1347 and 1353, killing a huge share of the population. What this study traces is everything after. They found repeated fresh introductions of plague into Estonia, beginning as early as the late 14th century. Professor Kristiina Tambets said: "We found evidence for repeated introductions of plague into Estonia starting already in the late 14th century." Around 1450 to 1500, the plague lineages went through a major expansion, splitting into three branches. The researchers think these branches probably established themselves in new animal populations, most likely rodents, creating fresh reservoirs from which outbreaks could keep emerging. Two things appear to have helped. One was climate: a period known as the Great Renaissance Drought. The other was war. The Thirty Years' War and the Great Northern War moved troops and displaced civilians across Europe, and plague travelled with them. The team also solved a technical problem. Ancient samples are usually dated by the archaeological layer they came from, and that can span more than a century. Dr Marcel Keller explained that such a range "limits our ability to interpret the genetic data". The researchers developed a way to date genomes more precisely using the evolutionary tree itself, which let them tie nearly all known plague genomes to specific historical outbreaks.

Why this matters

Most of us learn about the Black Death as a single catastrophe with a start and an end. This research shows something different and, in a way, more unsettling. The plague did not burn through Europe and vanish. It settled in. It found places to live between outbreaks, and it came back when conditions suited it. That is a pattern epidemiologists recognise today. A disease that can survive in an animal population has somewhere to wait. Getting rid of it in humans is not the same as getting rid of it. The finding about war is worth sitting with too. It was not only the bacterium that spread the plague. It was armies moving, people fleeing, towns filling with refugees, and food supplies collapsing. The biology and the history are not separate stories. The climate link fits a similar pattern. Drought changes where rodents live and how they behave, which changes how often they meet people. There is a modern relevance, though it should not be overstated. Plague still exists. It occurs in parts of Africa, Asia and the Americas, including a small number of cases in the western United States each year. It is now treatable with antibiotics when caught early. It is not a threat to daily life in the UK. The better reason to care is methodological. Being able to date ancient genomes precisely, and match them to recorded outbreaks, turns scattered archaeological finds into a connected history. That same approach can be used on other diseases.

What the evidence actually says

This is strong work, and it is worth being clear about why, and about where the limits are. Seventy-five genomes across four centuries is a lot for ancient DNA. These samples are fragile, usually degraded, and easily contaminated by modern material. Recovering 26 new ones from 11 sites is a substantial piece of laboratory work. The geographical spread, from England to Russia, means the conclusions are not based on one unusual region. There is an obvious limit, though, and it is one all ancient DNA shares: you can only study what has survived and been found. Burial sites are not evenly spread across Europe, and excavation follows modern priorities and funding. Gaps in the map may mean gaps in the record, not gaps in the plague. The claim that expanding lineages established new rodent reservoirs is an inference from the genetic pattern, not a direct observation. It is a reasonable reading, and it matches what is known about how plague behaves, but nobody sampled a 15th-century rat. The climate and war links are similar. They are correlations between the genetic timeline and the historical record. They are plausible and well argued. They are not proof of cause. The new dating method is the part most likely to matter long term, and it will be tested as other groups apply it.

Practical advice

There is nothing to do here for your own health, and that is worth saying plainly so nobody worries unnecessarily. Plague is not a risk in the UK. If you are travelling to a country where plague occurs, the FCDO travel advice pages and the National Travel Health Network's TravelHealthPro site carry current information. Cases are rare and usually linked to contact with wild rodents or their fleas. If history is what draws you here, this is a good example of how much archaeology has changed. Sites excavated decades ago are still yielding new information, because the techniques for reading DNA keep improving. Local museums and county archaeology services often welcome volunteers. And if there is a general lesson worth carrying, it is about reservoirs. Diseases that can live in animals are much harder to eliminate than diseases that only live in people. That is why smallpox could be wiped out and why others cannot be. It is a useful thing to understand when reading about any outbreak.

What to know

Researchers led by the University of Tartu reconstructed 26 new plague genomes from 11 archaeological sites in Estonia, Russia, England, the Netherlands and Switzerland, and combined them with 64 existing ones to build a picture spanning the 14th to 18th centuries. Plague did not end with the Black Death. It returned repeatedly for more than 400 years, with fresh introductions into Estonia from the late 14th century onwards. Around 1450 to 1500 the bacterium's family tree split into three expanding branches, probably as it established new animal reservoirs. Drought and the movement of armies during the Thirty Years' War and Great Northern War appear to have helped it spread. The team also developed a method to date ancient genomes far more precisely, letting them link nearly all known plague genomes to specific recorded outbreaks. The reservoir idea is an inference rather than a direct observation, and ancient DNA can only tell us about the sites that have been excavated. Plague is not a health risk in the UK. Sources: ScienceDaily, "Ancient DNA reveals how plague kept returning for 400 years after the Black Death", 20 September 2026, https://www.sciencedaily.com/releases/2026/09/260919031025.htm; Proceedings of the National Academy of Sciences, 2026; 123(37), https://doi.org/10.1073/pnas.2534899123; University of Tartu, https://ut.ee/en This article is for general information and does not replace advice from a doctor, pharmacist or other qualified healthcare professional.

#ancient DNA#plague#Black Death#genomics#archaeology#epidemics

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