González-Candelas, FernandoAstray, JenaroAlonso, JordiCastro, AdyCantón, RafaelGalán, Juan CarlosGarin, OlatzSáez, MarcSoldevila, NuriaBaricot, MaretvaCastilla, JesúsGodoy, PereDelgado-Rodríguez, MiguelMartín, VicenteMayoral, José MaríaPumarola, TomásQuintana, José MaríaTamames, SoniaDomínguez, Angela2013-01-212013-01-212012-03-07González-Candelas F, Astray J, Alonso J, Castro A, Cantón R, Galán JC, et al. Sociodemographic factors and clinical conditions associated to hospitalization in influenza A (H1N1) 2009 virus infected patients in Spain, 2009-2010. PLoS ONE; 7(3):e33139http://hdl.handle.net/10668/748Journal Article; Multicenter Study; Research Support, Non-U.S. Gov't;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.enSubtipo H1N1 del Virus de la Influenza AGripe humanaMedical Subject Headings::Named Groups::Persons::Age Groups::AdolescentMedical Subject Headings::Named Groups::Persons::Age Groups::AdultMedical Subject Headings::Named Groups::Persons::Age Groups::Adult::Aged::Aged, 80 and overMedical Subject Headings::Analytical, Diagnostic and Therapeutic Techniques and Equipment::Investigative Techniques::Epidemiologic Methods::Epidemiologic Study Characteristics as Topic::Epidemiologic Studies::Case-Control StudiesMedical Subject Headings::Named Groups::Persons::Age Groups::ChildMedical Subject Headings::Named Groups::Persons::Age Groups::Child::Child, PreschoolMedical Subject Headings::Check Tags::FemaleMedical Subject Headings::Analytical, Diagnostic and Therapeutic Techniques and Equipment::Therapeutics::Patient Care::HospitalizationMedical Subject Headings::Organisms::Eukaryota::Animals::Chordata::Vertebrates::Mammals::Primates::Haplorhini::Catarrhini::Hominidae::HumansMedical Subject Headings::Named Groups::Persons::Age Groups::InfantMedical Subject Headings::Named Groups::Persons::Age Groups::Infant::Infant, NewbornMedical Subject Headings::Organisms::Viruses::Vertebrate Viruses::RNA Viruses::Orthomyxoviridae::Influenzavirus A::Influenza A virus::Influenza A Virus, H1N1 SubtypeMedical Subject Headings::Diseases::Virus Diseases::RNA Virus Infections::Orthomyxoviridae Infections::Influenza, HumanMedical Subject Headings::Check Tags::MaleMedical Subject Headings::Named Groups::Persons::Age Groups::Adult::Middle AgedMedical Subject Headings::Health Care::Environment and Public Health::Public Health::Disease Outbreaks::Epidemics::PandemicsMedical Subject Headings::Analytical, Diagnostic and Therapeutic Techniques and Equipment::Investigative Techniques::Epidemiologic Methods::Statistics as Topic::Probability::Risk::Risk FactorsMedical Subject Headings::Geographicals::Geographic Locations::Europe::SpainMedical Subject Headings::Named Groups::Persons::Age Groups::Adult::Young AdultMedical Subject Headings::Named Groups::Persons::Age Groups::Adultresearch article22412995open access10.1371/journal.pone.00331391932-6203