In the last two weeks, 474,000 people in France were reported to have visited the doctor for acute diarrhea, or 410 per 100,000, more than the 283 per 100,000 definition of an epidemic, health officials said.
The stomach flu came right on the heels of a flu epidemic that involved more than 500,000 people getting treated by their doctor, officials said.
Doctors said they expected the number of cases of acute diarrhea to start going down next week.
Experts identified the virulent norovirus as the cause of the majority of cases of gastroenteritis among people age 5 and older in France in 2012, Radio France Internationale reported.
The flu epidemic has affected even more people, 545,000 last week, or 297 per 100,000.
The worst of the flu was found in the central Auvergne region, where 597 per 100,000 people said they have visited the doctor.