Doctors from Sentinelle, which monitors outbreaks of gastroenteritis, have noticed a huge rise in the number of consultations for acute diarrhea - the main symptom of winter stomach flu in certain parts of France.
The regions badly affected by the epidemic are Provence-Alpes-Côte d'Azur, the Grand Est, Pays de la Loire and Hauts-de-France.
And the bad news is doctors believe the number of cases of "gastro" will only rise in the coming weeks.
They predict the national threshold for epidemic will be reached at the beginning of next week.
Health officials say the best way to avoid getting sick is to avoid contact with dirty hands. However, if you can't avoid touching others, make sure to disinfect your hands quickly.
If you do get sick, the most important thing is to remain hydrated and avoid eating foods that are high in fibre.
Health experts advise drinking at least two litres of water a day.