Highlights from the Midi-Pyrénées Regional Health Agency

Summary of severe influenza cases during the winter epidemicThe 2011–2012 season was marked by a late-onset influenza epidemic of moderate intensity, dominated by the A(H3N2) virus, and a very high number of clustered cases of acute respiratory infections (ARIs) in elderly care facilities.Initiated during the 2009 influenza pandemic caused by the A(H1N1) virus, surveillance of severe influenza cases (patients hospitalized in intensive care) was continued during the 2011-2012 winter season across all intensive care units in France. The objectives of this surveillance are to assess the severity of the epidemic and to identify risk factors for severe influenza. During the 2009-2010 pandemic, it helped confirm the existence of risk factors such as obesity and pregnancy. It also allows for the estimation of the influenza vaccine’s efficacy.Nationally, by week 16, 320 severe cases had been reported since the start of surveillance in November 2011, primarily adults with risk factors who were infected with the A(H3N2) virus. These data confirmed the reduced effectiveness of the influenza vaccine in preventing severe cases this season. Vaccine effectiveness was estimated using the rapid method among at-risk individuals with confirmed influenza; it fell from 53% (95% CI: 40–67) in 2010–11 to 30% [95% CI: 22–39] in 2011–12 (results presented in a Eurosurveillance article). In Midi-Pyrénées, surveillance led by the Cire was conducted with the participation of 24 hospital departments: all intensive care units and some critical care units, from early November 2011 (week 44) to mid-April 2012 (week 15). A total of 6 severe cases were reported, 5 infected with an influenza A virus, including one A(H1N1) (the other viruses were not subtyped), and 1 infected with a type B virus. All patients were over 50 years of age, and two-thirds were over 65. Half of them had a risk factor targeted by seasonal influenza vaccination: age over 65 and/or specific chronic conditions. Four patients had not been vaccinated against influenza (one case vaccinated, information missing for one case). Three patients died; the other three were discharged after a favorable course of illness.