Molecular Archaeology Uncovers Dual Pathogen Threat in Napoleon's 1812 Retreat

A groundbreaking DNA analysis of remains from Napoleon’s catastrophic 1812 retreat from Russia has revealed a more complex microbial threat than previously understood, offering a molecular perspective on the downfall of the Grande Armée. The investigation, led by Nicolás Rascovan of the Institut Pasteur, focused on the dental pulp of thirteen soldiers exhumed from a mass grave near Vilnius, Lithuania, a critical point along the army's arduous withdrawal path.

The study, formally published in the journal Current Biology on October 24, 2025, identified the genetic signatures of two significant bacterial agents previously not confirmed in this cohort. Researchers detected Salmonella enterica, the cause of debilitating paratyphoid fever, in four individuals, and Borrelia recurrentis, which precipitates relapsing fever, in at least one soldier. This finding adds crucial detail to the historical narrative, which had often prioritized typhus as the primary infectious killer.

In a notable departure from prior assumptions, the genomic sequencing yielded no detectable trace of Rickettsia prowazekii, the bacterium responsible for typhus, in this specific sample group. This suggests that while typhus may have been present, the simultaneous onslaught of paratyphoid and relapsing fevers severely compromised the troops' resilience. The simultaneous presence of these different infectious agents likely transformed a military defeat into a demographic catastrophe.

Historical context indicates that the army, which began with over 600,000 men, suffered immense logistical breakdown, leading to poor sanitation that created ideal conditions for pathogens like those caused by Salmonella and Borrelia to spread through weakened ranks. While extreme winter conditions are frequently cited as the main cause of death, this scientific data suggests the environmental pressures were compounded by a biological assault. The findings imply that the vulnerability of even the most formidable human organization can be determined by its preparedness against unseen, microscopic adversaries.

The research team utilized next-generation sequencing, specifically shotgun sequencing, to cast a wider net for microbial DNA fragments, a technique that provided more comprehensive results than older, targeted PCR methods used in previous analyses of remains from the same site. This molecular evidence now serves as a powerful mirror reflecting how a combination of factors—strategy, environment, and a diverse array of infectious diseases—ultimately dictated the trajectory of the campaign.