Study IDs Bacteria That Felled Napoleon's Army

In 1812, Napoleon's Grande Armée marched into Russia with more than 600,000 soldiers, only to be decimated not just by battle, but by disease on a massive scale. According to new research, it was not just typhus and trench fever, as was previously thought, that devastated the French forces during the infamous retreat from Moscow—two other bacterial infections played a key role, NBC News reports. Scientists analyzed DNA extracted from the teeth of 13 soldiers who died during the retreat and uncovered evidence of two pathogens previously undocumented in this context: Salmonella enterica, which causes paratyphoid fever, and Borrelia recurrentis, the culprit behind louse-borne relapsing fever.

These microbes thrive in conditions of poor hygiene, which was rampant among the exhausted, freezing troops. The symptoms described in historical records—fevers, diarrhea, and general debilitation—are consistent with these diseases. The study's authors suggest that a mix of hunger, extreme fatigue, harsh weather, and multiple infections created a perfect storm, Live Science reports. While relapsing fever isn't "necessarily fatal," it could have sapped the strength of already weakened soldiers, making survival even less likely, researchers say.

The study, published in Current Biology, did not find typhus in these particular remains, although an earlier study did. Researchers say the two findings together highlight just how widespread infectious diseases were in the ranks. In the end, the army was nearly decimated, with hundreds of thousands dying before troops retreated.