Napoleon’s soldiers who died in Russian retreat had unexpected diseases, study finds

When Napoleon ordered his army to retreat from Russia in October 1812, disaster ensued. Starving, cold, exhausted and struggling with sickness, an estimated 300,000 soldiers died.

Researchers now say they have identified two unexpected diseases among soldiers who died in the retreat – paratyphoid fever and relapsing fever – which provide fresh insights into their plight.

“I think that the key thing of why [the retreat] was such a failure was the cold and the hunger and so on. With or without infectious diseases, they would have died massively anyway,” said Nicolás Rascovan, the head of the microbial paleogenomics unit at the Institut Pasteur and an author of the study. “But I think what this [does] change is some of our knowledge of all the infectious diseases.”

Writing in the journal Current Biology, Rascovan and his colleagues describe how previous analyses of DNA from soldiers buried in the same mass grave in Vilnius, Lithuania, had revealed evidence of typhus and trench fever.

However, that work was based on a very sensitive technique, called nested PCR, which involved screening samples for particular pathogens.

Using a different technique, called shotgun sequencing, Rascovan’s team was able to look for fragments of DNA that matched any out of 185 bacteria known to cause disease in humans.

The results, based on DNA from the teeth of 13 soldiers who had not previously been studied, revealed one soldier had been infected with the louse-borne bacterium Borrelia recurrentis, which causes relapsing fever, and four others had been infected with a type of the bacterium Salmonella enterica, which causes paratyphoid fever, a disease spread by contaminated food or water. One of these four soldiers might also have had relapsing fever, the team said.

The researchers say the findings fit with historical descriptions of the symptoms experienced by soldiers of Napoleon’s Grand Armée, such as fever and diarrhoea.

Unlike the previous studies, however, the team found no traces of the bacteria that cause typhus or trench fever. While Rascovan noted it could be that these soldiers were not infected with those diseases, or had only a mild infection, the results could alternatively be explained by the breakdown of ancient DNA over time, or that the quantity of DNA present was below the detection limit of the technique used.

The researchers carried out a number of statistical tests and analyses to ensure their results were robust and pointed to genuine infections. These included looking for the signs of DNA degradation that would be expected from authentic ancient DNA, and exploring where the DNA belonged on the evolutionary “family tree” of the two bacteria.

“In light of our results, a reasonable scenario for the deaths of these soldiers would be a combination of fatigue, cold, and several diseases, including paratyphoid fever and louse-borne relapsing fever. While not necessarily fatal, the louse-borne relapsing fever could significantly weaken an already exhausted individual,” they write.

Dr Michael Rowe, an expert in European history at King’s College London, welcomed the study.

“The science is interesting because I think it does something which a historian couldn’t do,” he said, referring to the identification of the diseases.

But he cautioned against assuming the devastation of the army was simply down to harsh weather that left soldiers susceptible to starvation and disease – a view Napoleon promoted.

“That underplays the Russians and it underplays the fact that they actually do some very clever things and that they [have] got a very good strategy and they’ve got actually quite a sophisticated army,” he said.