Highlights - Summary of the 2012-2013 Flu Season

Although sporadic influenza viruses are still being detected in the population, the 2012-2013 flu season is coming to an end. These indicators will be presented again in the epidemiological update starting next October.

Nationally The 2012-13 season was marked by a flu epidemic of moderate intensity but exceptional duration. According to data from the Unified Network (Grog and Sentinelles Network), the epidemic, which began in week 51, peaked in week 6 (incidence rate of 942 per 100,000 [914–970]). The peak number of emergency department visits for influenza or influenza-like illness in the departments participating in the Oscour network was reached in week 5. Virological surveillance indicates an influenza epidemic dominated by the circulation of three B viruses, A(H1N1)pdm09, and A(H3N2), with no particular severity. The percentage of positive influenza samples peaked in week 6. Since November 1, 2012, 751 severe influenza cases admitted to intensive care units (median age 58 years, 77% with risk factors, 68% type A virus) have been reported to the InVS (peak in week 6). Among these cases, 128 deaths occurred (median age 61 years, 83% with risk factors, and 72% type A virus). The case fatality rate (17%) remains significantly lower than that observed during the 2009 pandemic. In long-term care facilities for the elderly, 701 outbreaks of acute respiratory infections (ARI) have been reported since week 40 (peaking in week 7), 28% of which met severity criteria.

At the regional level: All data sources in Midi-Pyrénées showed an initial increase in influenza/influenza-like illness indicators around week 52, peaking in week 6. During week 6, the estimated incidence rate of influenza-like illness reached 1,301 cases per 100,000 inhabitants [1,148–1,454] according to the Unified Network, 2.4% of emergency department visits were recorded with a diagnosis of influenza/influenza-like illness according to the Oscour network, and 2.2% of calls handled by SOS Médecins 31 involved a diagnosis of influenza/influenza-like illness. According to the virology laboratory at Toulouse University Hospital, influenza viruses began to be detected in week 51, and the percentage of positive influenza test results peaked at 28% in week 6. Since November 1, 2012, 7 severe cases of influenza admitted to intensive care units in Midi-Pyrénées (4 children and 3 adults, 57% with risk factors, 57% type A virus) have been reported to the InVS. Among these cases, 2 deaths occurred in young children with type B virus, including one with no known risk factor. In long-term care facilities for the elderly, 30 outbreaks of acute respiratory infections (ARI) have been reported since week 40.