A pioneering study, set to be published in the esteemed journal Current Biology, leverages state-of-the-art ancient DNA sequencing techniques to dissect the microbial casualties hidden within the remains of Napoleon’s fallen soldiers. By extracting genomic material from dental samples retrieved from a mass grave in Vilnius, Lithuania—a key location on the army’s retreat path—researchers have unraveled the identity of the infectious agents involved in the epidemic that ravaged the troops. Contrary to longstanding beliefs, the microbial fingerprints of typhus were conspicuously absent. Instead, the team detected the genomic signatures of Salmonella enterica and Borrelia recurrentis, pathogens responsible for paratyphoid fever and relapsing fever, respectively.

The study’s lead author, Dr. Nicolás Rascovan from the Institut Pasteur in France, emphasizes the revolutionary nature of applying modern genomic tools to historical epidemics. “Using today’s technological capabilities to diagnose diseases that haunted soldiers over two centuries ago is nothing short of groundbreaking,” he states. This paradigm shift challenges the prevailing historiographical consensus and underscores the vital role of molecular paleopathology in revisiting the past.

For years, typhus was deemed the principal culprit behind the epidemic that decimated Napoleon’s Grande Armée during the Russian campaign. Historical medical accounts recount the prevalence of typhus symptoms among soldiers, and the presence of body lice—known vectors for Rickettsia prowazekii, the typhus bacterium—on skeletal remains supported this theory. Additionally, prior studies employing polymerase chain reaction (PCR) methods claimed to have detected R. prowazekii DNA fragments in remains from the same battlefield site. However, the new study’s unbiased metagenomic sequencing approach offers a more comprehensive survey of all bacterial DNA present, thereby refuting the previous typhus hypothesis.

A critical methodological advancement distinguishing this research is the application of shotgun sequencing optimized for heavily degraded ancient DNA. Unlike PCR, which amplifies specific DNA regions and requires relatively intact genetic templates, shotgun metagenomics captures the entirety of DNA fragments within a sample, no matter how fragmented. This methodological nuance mitigates amplification biases and enhances pathogen detection sensitivity, enabling researchers to reconstruct a broader spectrum of infectious agents with unprecedented resolution.

The research team meticulously processed and purified dental pulp from thirteen soldiers, extracting ancient DNA while rigorously eliminating contemporary environmental contaminants. This analytical rigor allowed for the detection of Salmonella enterica DNA, implicating enteric fever as a likely significant contributor to mortality in the retreating army. Enteric fever, commonly associated with unsanitary conditions and contaminated food or water, could thrive under conditions of mass encampment and limited resources, precisely the context experienced by Napoleon’s forces during their harrowing retreat.

Further adding to the complexity of the pathogen landscape, the team identified Borrelia recurrentis DNA, the spirochetal agent responsible for relapsing fever, a disease also vectored by body lice. Remarkably, the Borrelia lineage uncovered in the samples closely matched a strain historically found in Iron Age Britain over two millennia prior. This finding not only exemplifies the longevity and persistence of certain bacterial lineages within Europe but also enhances our understanding of the evolutionary trajectories of louse-borne diseases.

The absence of Rickettsia prowazekii and Bartonella quintana—another louse-associated pathogen causing trench fever—in the new sequencing data contrasts with earlier reports. This discrepancy likely stems from differences in sequencing methodologies and the inherent limitations of PCR-based detection in fragmented ancient DNA samples. The use of metagenomic sequencing now sets a new standard in paleomicrobiology, providing a more holistic and unbiased perspective on ancient pathogen communities.

This revelation has significant implications beyond historical clarification. It highlights the complexities of infectious disease transmission in wartime conditions and underscores the potential for multiple pathogens to synergistically exacerbate epidemic mortality. The co-occurrence of enteric and relapsing fevers likely created a deadly syndemic environment in the beleaguered army where overlapping symptoms and transmission pathways compounded the soldiers’ suffering.

Equally, this study exemplifies the transformative power of ancient DNA technologies in reconstructing infectious disease history. By unveiling pathogen genomes from centuries-old remains, researchers can trace the origins, migratory patterns, and persistence of virulent microbes across human epochs. For epidemiology, such insights provide invaluable context for understanding how diseases adapt and survive in human populations over time.

These findings prompt a reevaluation of historical medical diagnoses based solely on symptomatology and contemporary assumptions regarding disease prevalence. They offer cautionary lessons applicable to current and future epidemic responses by illustrating how complex pathogen landscapes can be obscured without comprehensive molecular scrutiny.

In conclusion, this groundbreaking research redefines the infectious diseases that plagued Napoleon’s army during its disastrous Russian retreat. The identification of Salmonella enterica and Borrelia recurrentis as key contributors challenges entrenched dogmas surrounding typhus and invites a more nuanced appreciation of the microbial dimensions of historical epidemics. This study stands as a paradigm for the fruitful integration of molecular genetics, history, and epidemiology, illuminating the shadows cast by past pandemics.

Subject of Research: People
Article Title: Paratyphoid Fever and Relapsing Fever in 1812 Napoleon’s Devastated Army
News Publication Date: 24-Oct-2025
Web References: http://www.cell.com/current-biology
References: Barbieri et al., “Paratyphoid fever and relapsing fever in 1812 Napoleon’s devastated army,” Current Biology, DOI: 10.1016/j.cub.2025.09.047
Image Credits: Michel Signoli, Aix-Marseille Université
Keywords: Medical histories; Pathogens; Bacterial pathogens; Infectious disease transmission; Disease outbreaks; Disease incidence; War; Ancient DNA

The Napoleonic invasion of Russia, famously marked by the severe winter of 1812 and relentless logistical failures, culminated in a catastrophic retreat through hostile terrain. Historians long suspected infectious diseases as a significant factor in the high mortality rates experienced by the Grande Armée, but direct proof remained elusive. To address this gap, researchers from the Institut Pasteur’s Microbial Paleogenomics Unit collaborated with specialists from Aix Marseille University, whose archaeological excavations in Vilnius, Lithuania, uncovered the remains of 13 French soldiers. These skeletal specimens, exhumed in 2002, became the basis for an ambitious attempt to genetically reconstruct the pathogens these soldiers harbored nearly two centuries ago.

The scientific approach combined next-generation sequencing (NGS) with stringent authentication protocols tailored for ancient DNA. Given that the DNA from archaeological remains is often fragmented and contaminated, the team developed a novel phylogeny-driven interpretive pipeline, in collaboration with genomic experts from the University of Tartu in Estonia. This approach scrutinizes genetic fragments against known bacterial genomes, confidently distinguishing genuine ancient pathogen DNA from modern contaminants, even when coverage is minimal. Through this meticulous method, the researchers detected robust genetic signatures of Salmonella enterica subsp. enterica serovar Paratyphi C—the agent of paratyphoid fever—and Borrelia recurrentis, the bacterium responsible for louse-borne relapsing fever.

These two distinct infectious agents, though epidemiologically different, manifest with similar clinical features such as cyclic high fevers, profound fatigue, and gastrointestinal distress. Paratyphoid fever arises from ingestion of contaminated food or water, while relapsing fever is vector-borne, transmitted by lice—both plausible in the cramped, unsanitary conditions of an army in retreat. The simultaneous presence of these pathogens likely exacerbated the soldiers’ vulnerability, compounding the already dire circumstances of freezing temperatures, starvation, and physical exhaustion. Out of the 13 individuals studied, four tested positive for S. enterica Paratyphi C, and two were positive for B. recurrentis, marking the first molecular confirmation of these agents in Napoleonic remains.

This revelation adds a critical dimension to the understanding of the Grande Armée’s collapse, supplementing previous studies that identified Rickettsia prowazekii—the cause of epidemic typhus—and Bartonella quintana, responsible for trench fever. The combined presence of these pathogens illustrates a grim cascade of infectious diseases that swept through Napoleon’s troops, likely contributing significantly to the staggering casualty figures. Historical records had described symptoms resembling these infections, but until now, molecular archaeology had not definitively linked the clinical observations to specific bacterial culprits.

Despite the breakthrough, the authors caution about extrapolating from the limited sample size—only 13 individuals were analyzed among the estimated thousands of soldiers who perished in the Vilnius burial grounds, and over 300,000 members of the Grande Armée died during the Russian campaign. The researchers stress that these findings do not quantify the exact role of infectious diseases relative to known environmental and logistical challenges—such as extreme cold, hunger, and battle wounds—but highlight infectious disease as a critical, previously underappreciated factor in the campaign’s fatal outcome.

The study’s success owes much to technological innovation. Ancient pathogen DNA typically exists in vanishingly low quantities and is fragmented due to degradation processes over centuries. Conventional genomic methods often fail to assemble complete pathogen genomes from such poor-quality material. The newly developed analytical pipeline incorporates phylogenetic frameworks to interpret sparse genomic fragments and authenticate ancient bacterial lineages. This enhances the sensitivity and specificity of pathogen detection, even in samples with limited DNA preservation, opening new avenues for paleomicrobiological research.

Nicolás Rascovan, lead researcher and head of the Microbial Paleogenomics Unit at Institut Pasteur, emphasizes the broader implications: “By accessing the genomic data of pathogens that circulated in historical populations, we gain invaluable insights into how infectious diseases evolved, spread, and sometimes vanished over time. Understanding the social and environmental contexts of these infections informs our knowledge today and improves our capacity to respond to present and future infectious threats.” This fusion of history with molecular biology not only elucidates a pivotal chapter in European military history but also enriches our understanding of pathogen dynamics within human populations.

The results also illuminate how multiple infectious threats can coexist and interact in vulnerable populations. Paratyphoid fever and relapsing fever, transmitted by distinct routes, afflicted clustered groups in conditions of poor hygiene and overcrowding—an epidemiological setting echoed in many historical and contemporary human crises. This study highlights the complex ecological networks of pathogens and vectors impacting soldiers forced into extreme conditions, revealing a multitude of biological stressors beyond what textual sources alone could capture.

Furthermore, this genetically informed perspective encourages a reevaluation of the role of infectious diseases in historical population declines and military failures, which often center on environmental, climatic, or strategic explanations. Advanced paleogenomic methods can uncover previously hidden contributors to mortality by decoding the microbial landscape within archaeological remains. As these technologies mature, the multidisciplinary collaboration among archaeologists, historians, and molecular biologists promises further transformative insights into past epidemics and their human tolls.

Napoleon’s failed 1812 Russian campaign remains emblematic of epic military hubris meeting natural adversity. This study reframes the narrative, showing that invisible microbial adversaries compounded the hardships faced by the Grande Armée as they suffered through bitter winters and relentless resistance. The integration of molecular data and historic accounts confirms that paratyphoid and relapsing fever were likely critical components in the army’s devastation. These findings resonate beyond history, informing contemporary scientific understanding of infectious disease evolution and outbreak dynamics within vulnerable populations.

As paleopathology and ancient genomics continue to expand their reach, such integrative research exemplifies how cutting-edge science can enrich and sometimes rewrite historical narratives. The work from Institut Pasteur and their partners demonstrates that the biological trace left by past pandemics and military campaigns is imprinted not just in chronicles, but deep within the DNA fragments preserved in human remains, waiting to be decoded by modern technology.

Subject of Research: Human tissue samples

Article Title: Paratyphoid fever and relapsing fever in 1812 Napoleon’s devastated army, Current Biology

News Publication Date: October 24, 2025

Web References:
https://doi.org/10.1016/j.cub.2025.09.047

References:
Rémi Barbieri, Julien Fumey, Helja Kabral, Christiana Lyn Scheib, Michel Signoli, Caroline Costedoat, Nicolás Rascovan, Current Biology, 24 October 2025.

Image Credits: © UMR 6578 Aix-Marseille Université, CNRS, EFS

Keywords: Paleogenomics, Infectious diseases, Human remains