Most of the victims were under 15 years old, this was the first epidemic in history

A groundbreaking study has revealed that the first recorded epidemic of plague occurred over 5,500 years ago among a small group of hunter-gatherers living near Lake Baikal in eastern Siberia. This discovery challenges long-held assumptions about the historical emergence of large-scale disease outbreaks. The research was conducted by an international team of scientists whose findings were published in *Nature*, one of the world's leading scientific journals. By analyzing ancient DNA extracted from human remains found at four burial sites of these early inhabitants, researchers identified previously unknown strains of the bacterium responsible for the plague, *Yersinia pestis*.

The study focused on the remains of individuals buried at four distinct locations around Lake Baikal. Using advanced DNA sequencing techniques, scientists reconstructed ancient bacterial genomes preserved in teeth, uncovering evidence of early forms of the plague-causing bacteria. These findings contradict the widely accepted belief that major disease epidemics did not exist before the Neolithic Revolution, when humans transitioned from nomadic hunting and gathering lifestyles to settled agricultural communities. According to Dr. Ruairidh Macleod, lead author of the study and researcher at the University of Oxford, this discovery provides clear evidence of a devastating plague outbreak that affected an entire community of hunter-gatherers in the Lake Baikal region, directly opposing previous understandings of disease history.

Plague is a highly contagious disease caused by the bacterium *Yersinia pestis*, which primarily affects rodents such as rats and mice. Transmission occurs when fleas bite infected rodents and then transfer the bacteria to other animals or humans through their bites. Once inside the flea’s digestive system, the bacteria remain there for up to three weeks before being excreted, often infecting another host upon biting. Historically, *Yersinia pestis* has been responsible for some of the deadliest pandemics in human history. For example, the Plague of Justinian, which spread from Central Asia to the Mediterranean between 541 and 767 AD, resulted in the deaths of approximately 40 million people. Similarly, the Black Death in the 14th century devastated Europe, killing an estimated 24 million people—about a quarter of the European and Western Asian population at the time. Another significant outbreak began in China in 1855 and later spread to Japan, India, Australia, and the Americas, claiming at least 15 million lives.

Thanks to advancements in ancient DNA sequencing technology, scientists have been able to detect the presence of *Y. pestis* in bones and teeth of individuals buried hundreds or even thousands of years ago. In this case, Dr. Macleod and his colleagues identified the bacterium in the remains of 18 out of 42 hunter-gatherers buried at four sites surrounding Lake Baikal. Researchers believe these individuals likely suffered from pneumonic plague, a form of the disease that attacks the lungs and spreads through airborne droplets expelled when an infected person coughs or sneezes. According to Macleod, the hunter-gatherers probably contracted the infection while hunting or consuming raw rodent meat. Rodents serve as reservoirs for the plague bacteria, and archaeological evidence suggests that people in the area frequently hunted them for food. Members of the community who hunted rodents or children who helped prepare rodent meat or hides could have acquired the bacteria from the blood or feces of the animals. Infected individuals could then transmit the disease to others through coughing or sneezing.

Dr. Macleod noted that people in this region still occasionally contract plague due to contact with rodents or consumption of undercooked rodent meat. For instance, media reports in 2020 described how a teenager in Mongolia died from plague after eating an infected rodent. Most victims in the Lake Baikal region during the ancient outbreak were very young, with two-thirds of them being under the age of 15. This pattern aligns with modern cases where children are particularly vulnerable to the disease due to their developing immune systems and close proximity to infected animals.

Dr. Hannes Schroeder, a paleogeneticist, commented on the study, emphasizing its significance in rewriting the narrative of human disease history. He highlighted that the identification of *Y. pestis* in such ancient remains opens new avenues for understanding how infectious diseases have shaped human populations throughout history. The study also raises questions about the potential role of early human societies in the transmission and evolution of pathogens. As more research is conducted using similar methods, scientists hope to uncover additional insights into the origins and spread of deadly diseases that have impacted humanity for millennia.