Scientists analyzing DNA from 13 soldiers buried in a mass grave in Vilnius, Lithuania, uncovered genetic traces of paratyphoid fever and louse-borne relapsing fever—offering the first direct confirmation of these pathogens in Napoleon’s Grande Armée. The study, published October 24, 2025, in Current Biology, links centuries-old eyewitness reports to modern genomics. ([sciencedaily.com](https://www.sciencedaily.com/releases/2025/10/251026021727.htm))
Napoleon’s invasion of Russia in 1812—often called the Patriotic War of 1812—ended in a disastrous retreat that devastated his forces. Contemporary estimates put the army’s size at roughly 500,000 to 600,000 troops, with about 300,000 deaths during the withdrawal amid cold, hunger, and poor sanitation. (sciencedaily.com)
To clarify the role of disease, researchers from the Institut Pasteur’s Microbial Paleogenomics Unit, working with the Laboratory of Biocultural Anthropology at Aix‑Marseille University, examined remains of 13 French soldiers exhumed in 2002 from a Vilnius burial site that holds more than 3,000 bodies. Using next‑generation sequencing on ancient DNA, they reported Salmonella enterica subsp. enterica serovar Paratyphi C in four individuals and Borrelia recurrentis—the louse‑borne cause of relapsing fever—in two. Both illnesses can produce high fever, exhaustion and digestive problems, aligning with historical descriptions of alternating bouts of fever and remission. (sciencedaily.com)
The authors describe this as the first direct genetic confirmation that paratyphoid and relapsing fevers were present in Napoleon’s army. The finding complements earlier PCR‑based work that detected DNA of Rickettsia prowazekii (typhus) and Bartonella quintana (trench fever) in other soldiers from the same Vilnius mass grave. (sciencedaily.com)
In the new analysis, the team did not authenticate reads for R. prowazekii or B. quintana in the 13 individuals studied, a result they caution does not rule out those pathogens’ presence during the broader campaign. Sample size and DNA preservation limit any estimate of prevalence. (research.pasteur.fr)
“Accessing the genomic data of the pathogens that circulated in historical populations helps us to understand how infectious diseases evolved, spread and disappeared over time … This information provides us with valuable insights to better understand and tackle infectious diseases today,” said Nicolás Rascovan, head of the Microbial Paleogenomics Unit at the Institut Pasteur and last author of the study. (pasteur.fr)
Methodologically, the group—working with collaborators at the University of Tartu in Estonia—developed and applied an authentication workflow, including a phylogeny‑driven interpretive approach, to identify ultra‑degraded pathogen DNA at low coverage and, in some cases, resolve lineages. (pasteur.fr)
The work was first posted as a bioRxiv preprint on July 16, 2025, and underwent peer review before publication in Current Biology on October 24, 2025 (DOI: 10.1016/j.cub.2025.09.047). Coverage by multiple outlets echoes the study’s central conclusion: disease compounded the harsh environmental and logistical stresses that overwhelmed the retreating army. (research.pasteur.fr)