title: Epidemiology of Hospital Admissions with Influenza during the 2013/2014 Northern Hemisphere Influenza Season: Results from the Global Influenza Hospital Surveillance Network.
abstract: The Global Influenza Hospital Surveillance Network was established in 2012 to obtain valid epidemiologic data on hospital admissions with influenza-like illness. Here we describe the epidemiology of admissions with influenza within the Northern Hemisphere sites during the 2013/2014 influenza season, identify risk factors for severe outcomes and complications, and assess the impact of different influenza viruses on clinically relevant outcomes in at-risk populations.
  
  
  
  Eligible consecutive admissions were screened for inclusion at 19 hospitals in Russia, Turkey, China, and Spain using a prospective, active surveillance approach. Patients that fulfilled a common case definition were enrolled and epidemiological data were collected. Risk factors for hospitalization with laboratory-confirmed influenza were identified by multivariable logistic regression.
  
  
  
  5303 of 9507 consecutive admissions were included in the analysis. Of these, 1086 were influenza positive (534 A(H3N2), 362 A(H1N1), 130 B/Yamagata lineage, 3 B/Victoria lineage, 40 untyped A, and 18 untyped B). The risk of hospitalization with influenza (adjusted odds ratio [95% confidence interval]) was elevated for patients with cardiovascular disease (1.63 [1.33-2.02]), asthma (2.25 [1.67-3.03]), immunosuppression (2.25 [1.23-4.11]), renal disease (2.11 [1.48-3.01]), liver disease (1.94 [1.18-3.19], autoimmune disease (2.97 [1.58-5.59]), and pregnancy (3.84 [2.48-5.94]). Patients without comorbidities accounted for 60% of admissions with influenza. The need for intensive care or in-hospital death was not significantly different between patients with or without influenza. Influenza vaccination was associated with a lower risk of confirmed influenza (adjusted odds ratio = 0.61 [0.48-0.77]).
  
  
  
  Influenza infection was detected among hospital admissions with and without known risk factors. Pregnancy and underlying comorbidity increased the risk of detecting influenza virus in patients hospitalized with influenza-like illness. Our results support influenza vaccination as a measure for reducing the risk of influenza-associated hospital admission.
authors.affiliation: Fundación para el Fomento de la Investigación Sanitaria y Biomédica de la Comunidad Valenciana (FISABIO), Valencia, Spain.
authors.forename: Joan
authors.initials: J
authors.lastname: Puig-Barberà
authors.affiliation: Fundación para el Fomento de la Investigación Sanitaria y Biomédica de la Comunidad Valenciana (FISABIO), Valencia, Spain.
authors.forename: Angels
authors.initials: A
authors.lastname: Natividad-Sancho
authors.affiliation: D.I. Ivanovsky Institute of Virology FSBI "N.F. Gamaleya FRCEM" Ministry of Health of Russian Federation, Moscow, Russian Federation.
authors.forename: Svetlana
authors.initials: S
authors.lastname: Trushakova
authors.affiliation: Research Institute of Influenza, St. Petersburg, Russian Federation.
authors.forename: Anna
authors.initials: A
authors.lastname: Sominina
authors.affiliation: Research Institute of Influenza, St. Petersburg, Russian Federation.
authors.forename: Maria
authors.initials: M
authors.lastname: Pisareva
authors.affiliation: National Influenza Reference Laboratory, Istanbul Faculty of Medicine, Istanbul University, Istanbul, Turkey.
authors.forename: Meral A
authors.initials: MA
authors.lastname: Ciblak
authors.affiliation: National Influenza Reference Laboratory, Istanbul Faculty of Medicine, Istanbul University, Istanbul, Turkey.
authors.forename: Selim
authors.initials: S
authors.lastname: Badur
authors.affiliation: Division of Infectious Disease, Key Laboratory of Surveillance and Early-Warning on Infectious Disease, Chinese Center for Disease Control and Prevention, Beijing, China.
authors.forename: Hongjie
authors.initials: H
authors.lastname: Yu
authors.affiliation: School of Public Health, Li Ka Shing Faculty of Medicine, The University of Hong Kong, Hong Kong Special Administrative Region, China.
authors.forename: Benjamin J
authors.initials: BJ
authors.lastname: Cowling
authors.affiliation: Sanofi Pasteur, Lyon, France.
authors.forename: Clotilde
authors.initials: C
authors.lastname: El Guerche-Séblain
authors.affiliation: Fundación para el Fomento de la Investigación Sanitaria y Biomédica de la Comunidad Valenciana (FISABIO), Valencia, Spain.
authors.forename: Ainara
authors.initials: A
authors.lastname: Mira-Iglesias
authors.affiliation: D.I. Ivanovsky Institute of Virology FSBI "N.F. Gamaleya FRCEM" Ministry of Health of Russian Federation, Moscow, Russian Federation.
authors.forename: Lidiya
authors.initials: L
authors.lastname: Kisteneva
authors.affiliation: Research Institute of Influenza, St. Petersburg, Russian Federation.
authors.forename: Kirill
authors.initials: K
authors.lastname: Stolyarov
authors.affiliation: National Influenza Reference Laboratory, Istanbul Faculty of Medicine, Istanbul University, Istanbul, Turkey.
authors.forename: Kubra
authors.initials: K
authors.lastname: Yurtcu
authors.affiliation: Division of Infectious Disease, Key Laboratory of Surveillance and Early-Warning on Infectious Disease, Chinese Center for Disease Control and Prevention, Beijing, China.
authors.forename: Luzhao
authors.initials: L
authors.lastname: Feng
authors.affiliation: Fundación para el Fomento de la Investigación Sanitaria y Biomédica de la Comunidad Valenciana (FISABIO), Valencia, Spain.|Centro de Investigación Biomédica en Epidemiología y Salud Publica (CIBER-ESP), Instituto de Salud Carlos III, Madrid, Spain.
authors.forename: Xavier
authors.initials: X
authors.lastname: López-Labrador
authors.affiliation: D.I. Ivanovsky Institute of Virology FSBI "N.F. Gamaleya FRCEM" Ministry of Health of Russian Federation, Moscow, Russian Federation.
authors.forename: Elena
authors.initials: E
authors.lastname: Burtseva
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D002648:Child; D002675:Child, Preschool; D002681:China; D016000:Cluster Analysis; D015897:Comorbidity; D062665:Epidemiological Monitoring; D005260:Female; D006801:Humans; D007223:Infant; D007231:Infant, Newborn; D007251:Influenza, Human / Q000453:epidemiology*; D008297:Male; D008875:Middle Aged; D015999:Multivariate Analysis; D016017:Odds Ratio; D009975:Orthomyxoviridae; D017063:Outcome Assessment, Health Care; D010343:Patient Admission; D011247:Pregnancy; D011251:Pregnancy Complications, Infectious; D011446:Prospective Studies; D012306:Risk; D012307:Risk Factors; D012426:Russia; D013030:Spain; D014421:Turkey; D055815:Young Adult