Napoleon’s retreat from Russia in 1812, one of the most tragic episodes in European history, reveals new unknown aspects through genetic analysis of ancient DNA. Researchers have identified pathogens that cause paratyphoid and relapsing fever in the skeletons of French soldiers in Vilnius, Lithuania.

The retreat of Napoleon Bonaparte and the Grand Army from Russia in 1812 was a disastrous campaign that marked the beginning of the end for his empire and his dominance in Europe, with around 300,000 soldiers losing their lives from a force that originally numbered almost half a million men.

A new study, based on DNA extracted from the teeth of 13 French soldiers buried in a mass grave in Vilnius along the route of retreat, offers a deeper understanding of the hardships experienced by the Grand Army by identifying two previously unrecorded pathogens in this historic event.

The discovery of the bacteria that cause paratyphoid and relapsing louse fever indicates, in conjunction with previous research, that multiple infections had spread among the soldiers, who were weakened by cold, hunger and exhaustion.

The burial ground in Vilnius, discovered in 2001, contains the remains of 2,000 to 3,000 soldiers of Napoleon’s army.

“Vilnius was a turning point on the retreat route of 1812. Many soldiers arrived there exhausted, hungry and sick. A significant number died and were quickly buried in mass graves,” said Nicolas Raskovan, a molecular biologist and geneticist who heads the microbial paleogenomes unit at the Pasteur Institute in Paris and lead author of the study published in the journal Current Biology.

“Although cold, starvation and typhus have long been considered the main causes of casualties, our results show that both paratyphoid fever and relapsing louse fever were present and may have contributed to the weakening and mortality of the soldiers,” Raskovan added.

Paratyphoid fever is usually spread through contaminated food or water, with symptoms including fever, headache, abdominal pain, diarrhea or constipation, weakness and sometimes a rash.

The form of relapsing fever identified is transmitted by body lice and causes repeated episodes of high fever, accompanied by headache, muscle aches and weakness.

In the study, four of the 13 soldiers tested positive for the paratyphoid fever bacterium and two for the relapsing fever bacterium. The symptoms of these two diseases agree with the descriptions found in historical accounts of the retreat.

An earlier 2006 study, which analyzed DNA from 35 other soldiers in the same cemetery, had identified the pathogens that cause typhus and trench fever, diseases with similar symptoms to paratyphoid and relapsing fever. The new study did not detect the presence of typhus or trench fever.

Napoleon led the Grand Army in the invasion of Russia in 1812, capturing Moscow, but the campaign collapsed, and he was forced to retreat due to insufficient supplies, counterattacks, and the severe Russian winter.

The new findings add a new dimension to the story of the ordeal of the French emperor’s soldiers, pointing to a complex epidemiological landscape where multiple infections were circulating at the same time, not one or two. While the study does not quantify the overall impact of the new pathogens or prove that they were widespread throughout the military, it does contribute to a better understanding of the medical complexities of the retreat.

“Ancient DNA allows us to identify infections that descriptions of symptoms are not enough to explain,” said Raskovan. “The coexistence of pathogens with different modes of transmission highlights how dire the sanitary conditions were at the time,” he added.

“Future research on more burial sites and individuals will allow a more detailed reconstruction of the epidemiological landscape of 1812.”

The study shows how the ever-evolving science of ancient DNA analysis can provide new evidence and a deeper understanding of historical events.

“Ancient DNA allows us to test historical hypotheses directly, adding evidence that can confirm or complicate narratives based on chronicles and descriptions of symptoms,” said Nikolas Raskovan.

“With careful identification, genomic research reveals which pathogens were there, how they evolved and survived, and how they spread, helping historians and scientists reconstruct complex crises with greater precision.”