IT IS ONE of history’s greatest military catastrophes — the collapse of Napoleon Bonaparte’s Grande Armée during the Russian campaign of 1812.
Now, a groundbreaking study published October 24, 2025 in Current Biology has shed fresh light on the mystery.
By extracting and sequencing ancient DNA from the teeth of 13 French soldiers buried in a mass grave in Vilnius, researchers unearthed direct evidence that two previously unsuspected pathogens — rather than only the traditionally blamed illnesses — ravaged the retreating forces.
The pathogens identified were Salmonella enterica subsp. enterica serovar Paratyphi C, responsible for paratyphoid fever, and Borrelia recurrentis, the louse-borne culprit behind relapsing fever. Four of the 13 tested soldiers carried the Salmonella DNA, and two harbored the Borrelia bacterium.
For decades, historians and medical experts believed that diseases like typhus and trench fever — both common scourges of 19th-century military camps — were the main microbial foes of Napoleon’s retreating army. Earlier studies had found lice on the remains and short DNA fragments attributed to the pathogens behind those diseases.
The new genomic analysis paints a more complex picture: these soldiers weren’t just victims of lice-borne infections or the brutal Russian winter. Instead, their immune systems may have been overwhelmed by a mixture of illnesses — including enteric disease from contaminated food or water, and high-fever episodes from louse-transmitted infection.
The detected infections match descriptions from contemporary accounts: reports of fever, diarrhea, exhaustion and recurring bouts of illness among retreating troops.
The Grande Armée set off for Russia in 1812 with roughly half a million men. By the end of the year — after a deadly combination of freezing cold, starvation, exhaustion, and relentless marching — only a small fraction remained. Estimates place total deaths at around 300,000.
Of course, disease was only one factor among many. Russian scorched-earth strategy, brutal winter conditions, logistical breakdowns, lack of adequate food and shelter all played massive roles. But the new DNA evidence underscores that infections — some previously unrecognized — helped speed the disintegration of what was once Europe’s most formidable army.
The co-occurrence of pathogens transmitted via different routes — through water/food (Salmonella) and lice (Borrelia) — also speaks to the appalling sanitary and living conditions the soldiers endured on their march. In crowded, lice-infested camps with limited access to clean water, both types of diseases could have spread rapidly.
The authors of the study, led by microbial paleogenomicists at Institut Pasteur in Paris and colleagues at Aix‑Marseille University, note that the sample size is small — just 13 soldiers out of thousands buried at Vilnius — meaning the findings cannot alone recast the entire narrative of the 1812 disaster.
Yet, this represents the first direct molecular confirmation of paratyphoid and relapsing fever in Napoleonic soldiers — a revelation only possible with modern DNA sequencing technology.
As ancient-DNA methods continue to improve, historians may expect more surprises: perhaps additional diseases, deeper insights into transmission paths, and a broader understanding of how microbial forces shaped one of history’s defining military collapses.
In the end, the story of Napoleon’s retreat may need to evolve: what was once conceived as a tragedy of cold and conflict now appears, at least in part, as a silent massacre by microbes.
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Dr. Joseph D. Lim, Ed. D., is the former Associate Dean of the College of Dentistry, University of the East; former Dean, College of Dentistry, National University; Past President and Honorary Fellow of the Asian Oral Implant Academy; Honorary Fellow of the Japan College of Oral Implantologists; Honorary Life Member of the Thai Association of Dental Implantology; and Founding Chairman of the Philippine College of Oral Implantologists. For questions on dental health, e-mail jdlim2008@gmail.com or text 0917-8591515.
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Dr. Kenneth Lester Lim, BS-MMG, DDM, MSc-OI, graduated Doctor of Dental Medicine, University of the Philippines, College of Dentistry, Manila, 2011; Bachelor of Science in Marketing Management, De la Salle University, Manila, 2002; and Master of Science (MSc.) in Oral Implantology, Goethe University, Frankfurt, Germany, 2019. He is an Associate Professor; Fellow, International Congress of Oral Implantologists; and Fellow, Philippine College of Oral Implantologists. For questions on dental health, e-mail limdentalcenter@gmail.com/PN
