During the retreat from French Emperor Napoleon Bonaparte’s Russian campaign in 1812, thousands of soldiers died of cold, hunger and disease. DNA analyzes now reveal which pathogens were rampant in Napoleon’s “Grande Armée” at the time. Accordingly, the soldiers at that time could have suffered primarily from typhoid and relapsing fever, instead of typhus and trench fever as previously assumed. Together with hunger and cold, these and probably other infectious diseases killed a large proportion of the soldiers.
By early 1812, much of Western and Central Europe was under French rule or dependent on France. The sphere of influence of Emperor Napoleon I Bonaparte extended from Spain through Central Europe and Italy to Austria-Hungary. But Napoleon wanted more: in the spring of 1812 he occupied two areas that were part of the Swedish territory and in the early summer he set off towards the east with a “Grande Armée” made up of more than half a million soldiers. The campaign of France and its allies against Russia and its ally Sweden had begun.
But the Russian campaign ended tragically: After Napoleon’s army initially advanced relatively quickly to the east, it had to endure several battles with heavy losses. Once in Moscow, the French and their allies discovered that the city had been evacuated by the Russians – there were no longer any politically relevant people there to capture or force to surrender. This meant that the conquest of Russia had failed and Napoleon’s army had to retreat in the harsh Russian winter – also because there was a lack of supplies and equipment. As a result, at least 300,000 soldiers of the Grande Armée died, and only a few reached their homeland.
Plagued by illness
“Russian attacks were not primarily to blame for these enormous losses, but rather the bitter cold of the Russian winter, together with hunger and disease,” explain Rémi Barbieri from the Pasteur Institute in Paris and his colleagues. This is supported, among other things, by an army doctor from Napoleon’s army, who reported typhus, diarrhea, fever, pneumonia and jaundice among the soldiers. The most common illnesses and possible causes of death for many soldiers were previously considered to be typhus, caused by the bacterium Rickettsia prowazekii, and trench fever, which is caused by the pathogen Bartonella quintana.
“The discovery of body lice on dead soldiers from Napoleon’s army supported this assumption, as lice are considered the main vectors of these pathogens,” report the researchers. In addition, a study in 2006 detected microbial DNA traces in some soldiers that appeared to come from these two pathogens. “However, these analyzes were limited by the technology available at the time and were based on only two short DNA fragments,” write Barbieri and his team. “As a result, the resolution was not high enough to clearly demonstrate the presence of these pathogens in Napoleon’s army.” This left it open as to which illnesses were really circulating in Napoleon’s “Grande Armée” during the retreat from Russia.
Evidence of typhus and relapsing fever
To provide greater clarity, Barbieri and his colleagues examined the remains of 13 Napoleonic soldiers who died and were buried in Vilnius, Lithuania, in late 1812. They used the most modern DNA sequencing methods that were not yet available in 2006. They compared the resulting sequences with the DNA of 185 known pathogens. Contrary to previous assumptions, these analyzes found no DNA traces of the pathogens of typhus or trench fever in the dead soldiers. “We were unable to detect Rickettsia prowazekii or Bartonella quintana in the samples,” wrote Barbieri and his team. However, they discovered the DNA of two other pathogens: the typhoid bacterium Salmonella enterica enterica and the pathogen that causes relapsing fever, Borrelia recurrentis.
This creates a new picture of the diseases rampant in Napoleon’s army. “Our study provides the first direct evidence that typhoid fever contributed to deaths during the catastrophic withdrawal from Russia,” wrote Barbieri and his colleagues. It is fitting that the army doctor De Kirckhoff reported severe diarrhea among the soldiers – and a possible source of infection: “Diarrhea was very common for us when we were in Lithuania,” writes De Kirckhoff. “One of the contributing factors was that in almost every house there we found barrels of salted beets, which we ate and whose juice we drank.” He suspected that these beets were to blame for the diarrhea. In fact, the typhoid pathogen is primarily transmitted through contaminated water or food. Although relapsing fever transmitted by body lice is not normally fatal, it could have further weakened soldiers weakened by hunger, cold and typhus.
Combination of several factors
The new analyzes reveal two pathogens that were not previously considered “culprits” for the diseases rampant among Napoleon’s soldiers. However, Barbieri and his colleagues assume that typhoid and relapsing fever were not the only infectious diseases circulating among the starving and freezing soldiers of the “Grande Armée”. “A plausible scenario for the deaths among Napoleon’s soldiers is a combination of exhaustion, cold, and several diseases, including typhus and relapsing fever,” the team writes. However, further research is necessary to clarify the true spectrum of infectious diseases that plagued Napoleon’s army as it retreated from Russia.
Source: Cell Press; Specialist article: Current Biology, doi: 10.1016/j.cub.2025.09.047