Scientists from the Institut Pasteur conducted genetic analyses on remains of soldiers from the 1812 Russian retreat. They detected two pathogens whose presence is consistent with symptoms described in historical accounts: paratyphoid fever and relapsing fever. The study is pre-published on
bioRxiv on July 16, 2025.
The famous Russian campaign led by Napoleon in 1812, also known as the
Patriotic War of 1812, led to the retreat of the Grand Army. Researchers from the Microbial Paleogenomics Unit at the Institut Pasteur investigated pathogens causing major infectious diseases at that time that could explain certain historical facts. To do this, they extracted and analyzed DNA from thirteen Napoleonic soldiers buried in Vilnius, Lithuania, using next-generation sequencing techniques applied to ancient DNA to identify potential infectious agents.
The research identified genetic signatures of two infectious agents:
Salmonella enterica subsp. enterica (
serovar Paratyphi C), responsible for paratyphoid fever, and
Borrelia recurrentis, responsible for relapsing fever, a disease transmitted by lice and characterized by febrile episodes interspersed with periods of remission. These two diseases, although distinct, can share certain symptoms such as high fever, fatigue, and digestive disorders, and their simultaneous presence may have contributed to worsening the soldiers' condition, already severely weakened by cold, hunger, and difficult sanitary conditions.
Of the teeth from thirteen Napoleonic soldiers exhumed in Vilnius, four tested positive for
S. enterica Paratyphi C and two for
B. recurrentis. Through this study, researchers provide the first genetic evidence of the presence of these two infectious agents, which had previously been little or not implicated, and whose exact impact on the high mortality suffered by the Grand Army during its retreat from Russia remains unknown. The presence of these two bacteria adds to the presence of the typhus agent, identified in a previous study and suspected from historical accounts:
Rickettsia prowazekii (responsible for typhus) and
Bartonella quintana (responsible for trench fever).
However, due to the small number of samples analyzed compared to the thousands of bodies found at the site, it is impossible to determine to what extent these pathogens contributed to the very high mortality observed. Indeed, the analysis is based on a limited number of samples (13 out of more than 3,000 bodies in Vilnius, among the 500,000 to 600,000 soldiers engaged and the approximately 300,000 deaths during the retreat).
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Accessing genomic data from pathogens that circulated in past populations allows us to understand how infectious diseases have evolved, spread, or disappeared throughout history, and to identify the social or environmental contexts that favored these events. This information provides valuable keys to better understand and combat today's infectious diseases," explains Nicolás Rascovan, head of the Microbial Paleogenomics Unit at the Institut Pasteur and last author of the study.
To achieve these results, the team developed, in collaboration with researchers from the University of Tartu in Estonia, an innovative authentication protocol that combines several validation steps, including an interpretation guided by the phylogeny of the highly fragmented genome fragments recovered. This approach allows for robust confirmation of the presence of a pathogenic species even when its DNA is preserved at very low coverage, and in some cases, to specify its belonging to a particular lineage.
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In most ancient human remains, pathogen DNA is extremely fragmented and survives only in very small proportions, making it very difficult to obtain complete genomes. Having methods capable of unambiguously identifying infectious agents from these weak signals, and sometimes even recognizing their lineages, is therefore essential for exploring the pathogenic diversity of the past," he adds.
This new study highlights the consistency between historical descriptions of diseases in the Grand Army and the typical symptoms of paratyphoid fever and relapsing fever. It provides new evidence for the hypothesis that infectious diseases also contributed to the collapse of the 1812 campaign alongside multiple other factors—exhaustion, extreme cold, and other harsh conditions.
It should be noted that Napoleon's Russian campaign in 1812 ended in military failure. This led to the retreat of the Grand Army, which allowed the Russian army to retake Moscow, thwarting the Emperor's strategy.
These results are pre-published on BioRxiv* and are awaiting peer review.