PARIS, FRANCE -- When Napoleon marched his Grand Army of 600,000 troops into Russia in 1812, he commanded one of the largest fighting forces the world had ever seen. Just months later, only a fraction remained, with some estimates putting the number as low as 50,000 men. Historians have long blamed the French general's disastrous retreat through the Russian winter, as the cold, starvation, and disease caused immeasurable loss of life. Typhus and trench fever have been traditionally considered as the major contributors to the death toll. However, according to a report by ZME Science, a new DNA study suggests that it was two lesser-known illnesses that may have seriously ravaged the ranks. Researchers from Paris Cité University's Institut Pasteur and other partner institutions extracted DNA from 13 teeth belonging to French soldiers from Napoleon's army, who had been buried in a mass grave in Vilnius, Lithuania. Surprisingly, they did not detect any microbes linked with typhus and trench fever, but instead identified genetic signatures for paratyphoid fever -- a gastrointestinal infection spread through contaminated food or water -- and relapsing fever, which is transmitted by lice. The study's authors stated that although these two illnesses may not have necessarily been fatal, they could have significantly weakened an already exhausted individual. For more on the archaeology of Napoleon's retreat from Russia, go to "The Grand Army Diet."