In the summer of 1812, French Emperor Napoleon Bonaparte set out to conquer Russia with about 500,000 soldiers. But by the end of that winter, only a very small number returned alive. Historically, the tragedy has been attributed to starvation, extreme cold, and epidemic typhus, but new research has overturned that view.
Researchers at the Pasteur Institute extracted and analyzed deoxyribonucleic acid (DNA) from the teeth of Napoleon's soldiers excavated in 2002 from a mass grave near Vilnius, Lithuania, and published the results on the 25th in the international journal Current Biology.
Epidemic typhus is an infectious disease caused by the bacterium Rickettsia prowazekii and is mainly spread by body lice. It causes severe headache, fever, chills, and rash. The claim that Napoleon's army died of epidemic typhus had its grounds. Not only did physicians of the time record such cases, but body lice, the primary vector that transmits epidemic typhus, were found on soldiers' remains, making it seem likely. DNA of the bacterium that causes epidemic typhus was also detected.
However, using the latest DNA analysis techniques, the team reached a different conclusion than before. An analysis of DNA remaining in the teeth of 13 soldiers found no trace of the typhus bacterium. Instead, two bacteria were identified: Salmonella enterica, which spreads through contaminated water or food, and Borrelia recurrentis, which is carried by body lice. They are pathogens that cause typhoid fever and relapsing fever, respectively.
In other words, it is more likely that Napoleon's army suffered from other infectious diseases such as typhoid fever or relapsing fever, rather than epidemic typhus. Typhoid fever causes high fever, abdominal pain, and dehydration, and also produces red spots. Relapsing fever brings high fever, chills, headache, muscle pain, joint pain, and rash. Given the extreme scarcity of food and sanitation amid Russia's severe cold at the time, such infections likely played a major role in the mass deaths of soldiers.
In particular, the researchers found that the Borrelia bacterium that caused relapsing fever belonged to the same lineage that existed about 2,000 years ago in Iron Age Britain. This means the same bacterium survived in Europe for thousands of years, providing a valuable clue for studying the evolutionary history of infectious diseases.
Nicolás Rascovan, a researcher at the Pasteur Institute who led the study, said, "It is very interesting that we were able to detect traces of disease buried 200 years ago using today's technology," and noted, "Ancient DNA analysis is a powerful tool to reconstruct the history of infectious diseases."
However, the team said, "Given that the number of samples analyzed is small compared with the thousands of bodies found, it is difficult to determine how much the detected pathogens affected mortality." From Oct. to Dec. 1812, at least 300,000 members of Napoleon's expeditionary force are believed to have died of starvation, cold, and disease during the retreat. In Vilnius, Lithuania, more than 3,000 bodies were found, and the researchers analyzed 13 of them.
Park Jong-hwa, a professor in the Department of Biomedical Engineering at the Ulsan National Institute of Science and Technology (UNIST), said, "Limitations remain in that the sample size is small, the DNA is fragmented, the genome coverage is low, and verification of environmental contamination DNA is limited," but added, "Socially, this can be seen as a small milestone study in the broader trend of historic scholarship becoming data-driven, and over the next few decades, the global trend of making such history scientific will expand significantly."
References
Current Biology (2025), DOI: https://doi.org/10.1016/j.cub.2025.09.047