title: Intensive care unit surveillance of influenza infection in France: the 2009/10 pandemic and the three subsequent seasons.
abstract: During the 2009/10 pandemic, a national surveillance system for severe influenza cases was set up in France. We present results from the system's first four years. All severe influenza cases admitted to intensive care units (ICU) were reported to the Institut de Veille Sanitaire using a standardised form: data on demographics, immunisation and virological status, risk factors, severity (e.g. acute respiratory distress syndrome (ARDS) onset, mechanical ventilation, extracorporeal life support) and outcome. Multivariate analysis was performed to identify factors associated with ARDS and death. The number of confirmed influenza cases varied from 1,210 in 2009/10 to 321 in 2011/12. Most ICU patients were infected with A(H1N1)pdm09, except during the 2011/12 winter season when A(H3N2)-related infections predominated. Patients' characteristics varied according to the predominant strain. Based on multivariate analysis, risk factors associated with death were age ≥ 65 years, patients with any of the usual recommended indications for vaccination and clinical severity. ARDS occurred more frequently in patients who were middle-aged (36-55 years), pregnant, obese, or infected with A(H1N1)pdm09. Female sex and influenza vaccination were protective. These data confirm the persistent virulence of A(H1N1)pdm09 after the pandemic and the heterogeneity of influenza seasons, and reinforce the need for surveillance of severe influenza cases.
authors.affiliation: Institut de Veille sanitaire (InVS), Saint-Maurice, France.
authors.forename: Isabelle
authors.initials: I
authors.lastname: Bonmarin
authors.forename: Emmanuel
authors.initials: E
authors.lastname: Belchior
authors.forename: Jean
authors.initials: J
authors.lastname: Bergounioux
authors.forename: Christian
authors.initials: C
authors.lastname: Brun-Buisson
authors.forename: Bruno
authors.initials: B
authors.lastname: Mégarbane
authors.forename: Jean Loup
authors.initials: JL
authors.lastname: Chappert
authors.forename: Bruno
authors.initials: B
authors.lastname: Hubert
authors.forename: Yann
authors.initials: Y
authors.lastname: Le Strat
authors.forename: Daniel
authors.initials: D
authors.lastname: Lévy-Bruhl
mesh_terms: D000293:Adolescent; D000328:Adult; D017677:Age Distribution; D000368:Aged; D000369:Aged, 80 and over; D002648:Child; D002675:Child, Preschool; D005260:Female; D005602:France / Q000453:epidemiology; D006760:Hospitalization / Q000706:statistics & numerical data*; D006801:Humans; D015994:Incidence; D007223:Infant; D007231:Infant, Newborn; D053118:Influenza A Virus, H1N1 Subtype / Q000302:isolation & purification*; D007251:Influenza, Human / Q000453:epidemiology / Q000401:mortality* / Q000473:pathology / Q000821:virology*; D007362:Intensive Care Units; D008297:Male; D008875:Middle Aged; D015999:Multivariate Analysis; D011159:Population Surveillance / Q000379:methods*; D012141:Respiratory Tract Infections / Q000401:mortality* / Q000473:pathology; D012307:Risk Factors; D012621:Seasons; D012720:Severity of Illness Index; D017678:Sex Distribution; D012959:Socioeconomic Factors; D055815:Young Adult
keywords: ICU; Influenza; SARI; pregnancy; surveillance; vaccine-preventable diseases