title: Sociodemographic factors and clinical conditions associated to hospitalization in influenza A (H1N1) 2009 virus infected patients in Spain, 2009-2010.
abstract: The emergence and pandemic spread of a new strain of influenza A (H1N1) virus in 2009 resulted in a serious alarm in clinical and public health services all over the world. One distinguishing feature of this new influenza pandemic was the different profile of hospitalized patients compared to those from traditional seasonal influenza infections. Our goal was to analyze sociodemographic and clinical factors associated to hospitalization following infection by influenza A(H1N1) virus. We report the results of a Spanish nationwide study with laboratory confirmed infection by the new pandemic virus in a case-control design based on hospitalized patients. The main risk factors for hospitalization of influenza A (H1N1) 2009 were determined to be obesity (BMI≥40, with an odds-ratio [OR] 14.27), hematological neoplasia (OR 10.71), chronic heart disease, COPD (OR 5.16) and neurological disease, among the clinical conditions, whereas low education level and some ethnic backgrounds (Gypsies and Amerinds) were the sociodemographic variables found associated to hospitalization. The presence of any clinical condition of moderate risk almost triples the risk of hospitalization (OR 2.88) and high risk conditions raise this value markedly (OR 6.43). The risk of hospitalization increased proportionally when for two (OR 2.08) or for three or more (OR 4.86) risk factors were simultaneously present in the same patient. These findings should be considered when a new influenza virus appears in the human population.
authors.affiliation: Unidad Mixta Genómica y Salud CSISP-Universitat de València, Valencia, Spain. fernando.gonzalez@uv.es
authors.forename: Fernando
authors.initials: F
authors.lastname: González-Candelas
authors.forename: Jenaro
authors.initials: J
authors.lastname: Astray
authors.forename: Jordi
authors.initials: J
authors.lastname: Alonso
authors.forename: Ady
authors.initials: A
authors.lastname: Castro
authors.forename: Rafael
authors.initials: R
authors.lastname: Cantón
authors.forename: Juan Carlos
authors.initials: JC
authors.lastname: Galán
authors.forename: Olatz
authors.initials: O
authors.lastname: Garin
authors.forename: Marc
authors.initials: M
authors.lastname: Sáez
authors.forename: Nuria
authors.initials: N
authors.lastname: Soldevila
authors.forename: Maretva
authors.initials: M
authors.lastname: Baricot
authors.forename: Jesús
authors.initials: J
authors.lastname: Castilla
authors.forename: Pere
authors.initials: P
authors.lastname: Godoy
authors.forename: Miguel
authors.initials: M
authors.lastname: Delgado-Rodríguez
authors.forename: Vicente
authors.initials: V
authors.lastname: Martín
authors.forename: José María
authors.initials: JM
authors.lastname: Mayoral
authors.forename: Tomás
authors.initials: T
authors.lastname: Pumarola
authors.forename: José María
authors.initials: JM
authors.lastname: Quintana
authors.forename: Sonia
authors.initials: S
authors.lastname: Tamames
authors.forename: Angela
authors.initials: A
authors.lastname: Domínguez
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D016022:Case-Control Studies; D002648:Child; D002675:Child, Preschool; D005260:Female; D006760:Hospitalization; D006801:Humans; D007223:Infant; D007231:Infant, Newborn; D053118:Influenza A Virus, H1N1 Subtype / Q000302:isolation & purification; D007251:Influenza, Human / Q000175:diagnosis / Q000453:epidemiology*; D008297:Male; D008875:Middle Aged; D058873:Pandemics; D012307:Risk Factors; D013030:Spain / Q000453:epidemiology / Q000208:ethnology; D055815:Young Adult