Headlines - Summary of the 2016-2017 Flu Season in Metropolitan France

The summary of surveillance data for the 2016-2017 flu season in mainland France has just been published on the Santé publique France website. This season began earlier than the previous six (since 2010-2011): it began in mid-December (Week 49/2016), peaked in mid-January (Week 3/2017), and ended in early February (Week 6/2017), for a total duration of 10 weeks (Figure). Caused almost exclusively by the influenza A(H3N2) virus, as observed across Europe, the epidemic was of moderate intensity in the outpatient setting (1.9 million people sought care for influenza-like illness according to data from the Sentinelles Network vs. 2.9 million in 2014–2015) but was particularly severe among the elderly. It was characterized by a high proportion of hospitalizations among emergency department visits for influenza-like illness (16% of 40,000 visits) and by a high proportion of people aged 65 and older among hospitalized patients (69%). This age group accounted for 67% of the 1,479 influenza cases admitted to intensive care. Nearly 2,000 episodes of acute respiratory failure occurred in long-term care facilities (86% of which began during the epidemic). This number of episodes—and particularly those attributed to influenza—was significantly higher than that observed during the previous four flu seasons. This epidemic was also marked by excess mortality estimated at 14,400 deaths attributable to influenza, more than 90% of which occurred among people aged 75 and older. Vaccination coverage among the at-risk population in mainland France remains very low and has declined since the 2009–2010 season, when it stood at 60%. This year, fewer than one in two at-risk individuals were vaccinated (46% for all individuals targeted by vaccination and 50% among those aged 65 and older, according to the French National Health Insurance). Even though the effectiveness of the influenza vaccine is most often moderate, or even low, in older adults, particularly against the A(H3N2) virus, the positive impact of seasonal flu vaccination on mortality among the elderly can be significant (as shown by an analysis of French data from 2000 to 2009, which estimated that vaccination prevented an average of more than 2,000 deaths each year and had an average efficacy of 35% in this age group).