Ancient DNA reveals disease that decimated Napoleon's troops in the Russian campaign

Beginning on June 24, 1812, approximately 600,000 soldiers led by French Emperor Napoleon Bonaparte crossed the Neman River to invade the Russian Empire. The war was one of the costliest in history, and just under six months later, only a few tens of thousands of men returned across the river. In early August, a preprint study, not yet peer-reviewed, by microbiologist Rémi Barbieri of the University of Paris and his team identified other pathogens that may indeed have been responsible for many of these deaths.

According to analysis of ancient DNA extracted from the teeth of 13 soldiers found in mass graves in Vilnius, Lithuania, Napoleon's troops retreating from Russia in 1812 were decimated not only by typhus, but also by paratyphoid fever and a relapsing fever transmitted by lice.

Historical documents from the period show that doctors accompanying the army diagnosed typhus based on symptoms such as fever, headache, and rash, and an analysis of remains in a 2006 study suggested possible infections with typhus and trench fever. At the time, there was no way to detect the presence of Rickettsia prowazekii, the bacterium responsible for epidemic typhus, or Bartonella quintana, the cause of trench fever, which infected more than a million soldiers during World War I. Doctors at the time documented cases of typhus, with symptoms that included fever, headache, and rash. "Although not necessarily fatal, louse-borne relapsing fever could significantly weaken an already exhausted individual," the researchers write.

The fact that the tests did not reveal traces of typhus does not mean that the disease did not contribute to the casualties: in addition to the 13 soldiers already examined, "analysis of a larger number of samples will be necessary to fully understand the spectrum of epidemic diseases that affected Napoleon's army during the Russian retreat," the researchers write. "In light of our results, a reasonable scenario for the deaths of these soldiers would be a combination of exhaustion, cold, and several diseases, including paratyphoid fever and louse-borne relapsing fever."