Ancient DNA discovers paratyphoid fever and relapsing fever among Napoleon’s soldiers

Scientists from the Pasteur Institute conducted a genetic analysis of the remains of former soldiers who withdrew from Russia in 1812. They detected two pathogens – those causing typhoid fever and relapsing fever, which correlate with the symptoms described in historical accounts. The study was published as a preprint on bioRxiv on July 16, 2025. It will be published in the journal on October 24.

The famous Russian campaign led by Napoleon in 1812, also known as the “Patriot War of 1812”, ended with the withdrawal of the French army. Scientists from the Department of Microbial Paleogenomics of the Institut Pasteur, in collaboration with the Laboratory of Biocultural Anthropology at the University of Aix in Marseille, decided to investigate which pathogens could have caused the serious epidemics of infectious diseases that contributed to this historic episode. They collected and analyzed the DNA of 13 Napoleonic soldiers exhumed in Vilnius, Lithuania, in 2002 during excavations conducted by a team specializing in archaeoanthropology at the University of Aix-Marseille. The scientists then used next-generation sequencing techniques applied to ancient DNA to identify potential infectious agents.

Their research identified genetic signatures of two infectious agents: subsp. (serotype Paratyphi C), responsible for paratyphoid fever and responsible for relapsing fever, a disease transmitted by lice and characterized by bouts of fever followed by periods of remission. Although the two diseases are different, they can cause similar symptoms such as high fever, fatigue and digestive problems, and their simultaneous occurrence may have contributed to the deterioration of the soldiers’ condition, especially since they were already weakened by cold, hunger and lack of hygiene.

Of the 13 Napoleonic soldiers exhumed in Vilnius, the teeth of four tested positive for Paratyphi C and two tested positive for . This study provides the first genetic evidence for the presence of these two largely unsuspected infectious agents, although their exact role in the large number of deaths during the withdrawal from Russia is unknown. Confirmation of the presence of these two bacteria comes after an earlier study identified the causative agent of typhus and trench fever, pathogens that have long been thought to be associated with retreat based on historical accounts.

Given the small number of samples analyzed compared to the thousands of bodies found, it is impossible to determine to what extent these pathogens contributed to the extremely high mortality rate observed. The scientists’ analysis was based on a limited number of samples (13 of over 3,000 bodies in Vilnius and approximately 500,000–600,000 armed forces soldiers, of whom approximately 300,000 died during the retreat).

“” – explains Nicolás Rascovan, head of the Department of Microbial Paleogenomics at the Institut Pasteur and the last author of the study.

To achieve these results, the team worked with scientists from the University of Tartu in Estonia to develop an innovative authentication process that included several steps, including a phylogeny-based interpretive approach for recovered highly degraded genome fragments. This method allows scientists to accurately identify pathogens even if their DNA provides only a small coverage, and in some cases even indicates a specific lineage.

“” – he adds.

A new study shows a correlation between historical descriptions of diseases suffered by Napoleon’s army and the typical symptoms of paratyphoid fever and relapsing fever. It provides new evidence to support the theory that infectious disease was one of the causes of the collapse of the 1812 campaign, along with many other factors such as exhaustion, extreme cold and harsh conditions.

The Russian campaign led by Napoleon in 1812 ultimately ended in military defeat, which resulted in the devastating retreat of the French army. This enabled the Russian army to regain control of Moscow and dealt a huge blow to the emperor’s strategy.