Researchers have identified genetic traces of two infectious diseases – paratyphoid fever and relapsing fever – in soldiers from Napoleon’s army who died during the disastrous retreat from Russia in 1812. The findings, published in Current Biology, suggest that these infections may have contributed to the collapse of the Grande Armée, which lost hundreds of thousands of men to illness, starvation, and exposure during the winter withdrawal.
The study analyzed ancient DNA extracted from the teeth of 13 soldiers recovered from a mass grave in Vilnius, Lithuania – a site associated with Napoleon’s retreat from Moscow. Using metagenomic sequencing and a phylogeny-based authentication workflow, the team detected Salmonella enterica subspecies enterica (Paratyphi C), the bacterium responsible for paratyphoid fever, and Borrelia recurrentis, the agent of louse-borne relapsing fever. Both infections cause fever, fatigue, and gastrointestinal or systemic symptoms, aligning with historical reports of illness among the French troops.
Earlier studies had implicated other pathogens – such as Rickettsia prowazekii (typhus) and Bartonella quintana (trench fever) – based on early PCR evidence and the discovery of lice among soldiers’ remains. However, the new analysis did not detect these organisms. Instead, high-throughput sequencing confirmed the presence of S. Paratyphi C and B. recurrentis through strict contamination controls and genomic authentication. Four of the 13 individuals yielded genetic evidence of S. enterica, and two tested positive for B. recurrentis.
Historical accounts by J.R.L. de Kirckhoff, a French military physician who served during the campaign, describe soldiers suffering from persistent diarrhea and fevers after arriving in Vilnius. He also recorded that troops consumed salted beets and brine from barrels found in abandoned houses, which may have introduced contaminated food or water. These descriptions are consistent with paratyphoid infection, though the overlapping symptoms of typhus, typhoid, and paratyphoid fever would have made clinical differentiation impossible at the time.
The researchers caution that the small number of samples analyzed cannot determine the full range of diseases that affected Napoleon’s soldiers. Still, the detection of two distinct pathogens supports the theory that multiple infections – exacerbated by exhaustion, malnutrition, and freezing conditions – contributed to the army’s devastation. The study highlights the growing role of ancient DNA analysis in reconstructing historical disease outbreaks and clarifying the causes of past epidemics.
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