Ancient DNA reveals the deadly diseases behind Napoleon’s defeat

Investigating the mystery of the decline of 1812

Napoleon’s invasion of Russia in 1812, known as the Patriotic War of 1812, ended in one of the most disastrous retreats in history. To better understand the role disease may have played in this collapse, researchers from the Institut Pasteur’s Paleomicrobial Genomics Unit collaborated with the Laboratory of Biocultural Anthropology at the University of Aix-Marseille. The team analyzed the DNA of 13 French soldiers exhumed in 2002 from a burial site in Vilnius, Lithuania, which was discovered during archaeological excavations led by the Aix-Marseille University group. Using next-generation sequencing technology of ancient DNA, they looked for genetic traces of infectious organisms.

Researchers have discovered two distinct disease factors: Salmonella enterica subsp. Intestinal (serovar Paratyphi C), which causes paratyphoid fever, and Borrelia recurrentThe bacteria responsible for relapsing fever. The latter is transmitted by lice and produces alternating periods of fever and recovery. Although the infections are different, both infections can cause high fever, fatigue, and gastrointestinal upset. Their combined effect would have exacerbated the soldiers’ suffering at a time when cold, hunger, and poor sanitation were already taking their toll.

Genetic evidence of Napoleon’s soldiers

Of the 13 soldiers tested, DNA was tested S. intestinalis Paratyphi C was found in four individuals, for. Frequent Detected in two. This represents the first direct genetic confirmation of the presence of these pathogens in Napoleon’s army. Their exact contribution to the massive death toll remains uncertain, but the findings complement previous research that has identified them Rickettsia prowaziki (cause of typhus) and Bartonella quintana (responsible for trench fever), both of which have long been suspected of spreading through the ranks during the retreat.

Because only a small number of samples can be analyzed compared to the thousands of remains in Vilnius, researchers cannot yet determine the extent of this infection. The soldiers tested represent a small percentage – 13 out of more than 3,000 bodies at the site and approximately 500,000 to 600,000 soldiers who participated in the campaign, of whom about 300,000 died during the withdrawal.

Understanding the past to protect the future

“Accessing genomic data for pathogens that have circulated in populations throughout history helps us understand how infectious diseases evolve, spread and disappear over time, and identify the social or environmental contexts that played a role in these developments,” explains Nicolas Rascovan, head of the Paleomicrobial Genomics Unit at the Pasteur Institute. “This information provides us with valuable insights to better understand and treat infectious diseases today.” And the final author of the study.

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

He adds: “In most ancient human remains, pathogenic DNA is highly fragmented and is only present in very low quantities, making it very difficult to obtain complete genomes. We therefore need methods capable of unambiguously identifying infectious agents from these weak signals, and sometimes even identifying lineages, to explore pathogen diversity in the past.”

Link history and disease

The team’s findings closely match historical descriptions of the fever that swept through Napoleon’s forces. This association supports the theory that infectious diseases contributed to the disastrous outcome of the 1812 campaign, along with other factors such as exhaustion, starvation, and the harsh Russian winter.

Napoleon’s campaign of 1812 ultimately ended in defeat, leading to a massive retreat that devastated his army. Russian forces recaptured Moscow, marking a turning point that dealt a fatal blow to Napoleon’s military ambitions.