French health watchdogs said on Wednesday the country was officially in the grip of a flu epidemic after 176,000 people had fallen sick, two of whom have died.
To be classified as an epidemic, new cases of influenza recorded by doctors have to number more than 174 per 100,000 people per week.
This threshold was breached last week, when there were 280 cases per 100,000 people.
Three viral strains are to blame, including A(H1N1) 2009, which emerged last year as the novel "swine" flu, according to the epidemiological networks Regional Flu Observation Groups (GROG) and Sentinelles, which is operated by the National Institute of Health and Medical Research (Inserm).
On December 23, Britain's health authorities said 27 people had died of flu, 24 of them from swine flu.
Agencies in both countries have urged people in at-risk groups -- particularly the elderly and those with respiratory problems -- to get vaccinated.
So-called "seasonal" flu epidemics are annual health problems in temperate countries with the onset of winter.
According to the World Health Organisation (WHO), flu epidemics result globally in about three to five million cases of severe illness per year and 250,000-500,000 deaths.