Journalism of Courage

DNA identifies 2 bacterial killers that stalked Napoleon’s army

When a group of French researchers set out to answer which infectious diseases helped fell the troops, they did not have much to go on: only 13 teeth from men buried in a mass grave in Vilnius, Lithuania.

October 25, 2025 09:29 AM IST First published on: Oct 25, 2025 at 09:28 AM IST
Napolean BonaparteWhile other infectious diseases are also suspected of playing a role based on historical accounts, this study adds two more killers to the record. (Wikimedia Commons Photo/ Representational)

Written by: Gina Kolata

Napoleon’s army was starving and freezing as it withdrew from the failed invasion of Russia in 1812. It was also stalked by additional killers: bacterial infections.

When a group of French researchers set out to answer which infectious diseases helped fell the troops, they did not have much to go on: only 13 teeth from men buried in a mass grave in Vilnius, Lithuania. They were among the doomed soldiers of an army dispatched by the French emperor that initially numbered around 500,000.

But each tooth had a dollop of tissue and blood inside that contained tiny fragments of microbial DNA. Using state-of-the-art methods, the researchers found evidence of two kinds of bacteria that had not previously been suspected of circulating among these troops.

One is relapsing fever, an infection carried by lice that resembles typhus. Like that disease, it causes high fevers, joint pain, severe headaches, nausea and vomiting, and extreme fatigue.

The other is paratyphoid fever, transmitted through contaminated food or water. Its symptoms include a high fever, headache, weakness and abdominal pain.

Their paper was published Friday in Current Biology.

While other infectious diseases are also suspected of playing a role based on historical accounts, this study adds two more killers to the record.

“This is really good work,” said Kyle Harper, a historian at the University of Oklahoma who was not involved in the study.

And, he said, “it’s an interesting historical case study,” of what he called “an extraordinary episode of human suffering.”

Nicolas Rascovan, an expert in ancient DNA at the Institut Pasteur in Paris and lead author of the new paper, said he by no means thought the two pathogens identified by his group were the sole cause of the demise of the troops.

Much more important, he said, was that the men were starving, dehydrated and freezing. The men, he said, were tottering on the edge of life and death.

“In those conditions,” he added, “any infectious disease can kill people.”

A French physician who was present during the campaign, Dr. JRL de Kirckhoff, had listed typhus, diarrhea, dysentery, fevers, pneumonia and jaundice among the diseases that afflicted the troops.

This article originally appeared in The New York Times.

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