Open Access Research article

Social factors related to the clinical severity of influenza cases in Spain during the A (H1N1) 2009 virus pandemic

José María Mayoral117*, Jordi Alonso23, Olatz Garín23, Zaida Herrador4, Jenaro Astray5, Maretva Baricot3, Jesús Castilla36, Rafael Cantón37, Ady Castro8, Miguel Delgado-Rodríguez39, Alicia Ferri3, Pere Godoy103, Fernando Gónzález-Candelas113, Vicente Martín123, Tomás Pumarola13, José María Quintana143, Núria Soldevila3, Sonia Tamames15, Ángela Domínguez163 and and the CIBERESP Cases and Controls in Pandemic Influenza Working Group, Spain

Author Affiliations

1 Servicio de Vigilancia epidemiológica de Andalucia, Sevilla, Spain

2 Institut Municipal de Investigació Mèdica, Barcelona, Spain

3 CIBER Epidemiología y Salud Pública, Barcelona, Spain

4 Programa de Epidemiología Aplicada de Campo, ISCIII, Madrid, Spain

5 Área de Epidemiología, Comunidad de Madrid, Madrid, Spain

6 Instituto de Salud Pública de Navarra, Pamplona, Spain

7 Hospital Universitario Ramón y Cajal, Madrid, Spain

8 CIBER Enfermedades Respiratorias _Instituto de Investigación Hospital 12 de Octubre, Madrid, Spain

9 Universidad de Jaén, Jaén, Spain

10 Departament de Salut, Generalitat of Catalonia, Barcelona, Spain

11 Centro Superior de Investigación en Salud Pública, Universitat de València, València, Spain

12 Instituto de Biomedicina, Universidad de Leon, Leon, Spain

13 Red Española de Investigación en Patología Infecciosa, Madrid, Spain

14 Unidad de Investigación, Hospital Galdakao-Usansolo, San Sebastian, Spain

15 Dirección General de Salud Pública e Investigación, Desarrollo e Innovación, Junta de Castilla y León, Valladolid, Spain

16 Departament de Salut Pública, Universitat de Barcelona, Barcelona, Spain

17 Sº de Epidemiología. Consejería de Salud. Andalucía, Avda. de la Innovación s/n, 41080, Sevilla, Spain

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BMC Public Health 2013, 13:118  doi:10.1186/1471-2458-13-118

Published: 7 February 2013

Abstract

Background

During the 2009 influenza pandemic, a change in the type of patients most often affected by influenza was observed. The objective of this study was to assess the role of individual and social determinants in hospitalizations due to influenza A (H1N1) 2009 infection.

Methods

We studied hospitalized patients (cases) and outpatients (controls) with confirmed influenza A (H1N1) 2009 infection. A standardized questionnaire was used to collect data. Variables that might be related to the hospitalization of influenza cases were compared by estimation of the odds ratio (OR) and 95% confidence intervals (CI) and the variables entered into binomial logistic regression models.

Results

Hospitalization due to pandemic A (H1N1) 2009 influenza virus infections was associated with non-Caucasian ethnicity (OR: 2.18, 95% CI 1.17 − 4.08), overcrowding (OR: 2.84, 95% CI 1.20 − 6.72), comorbidity and the lack of previous preventive information (OR: 2.69, 95% CI: 1.50 − 4.83). Secondary or higher education was associated with a lower risk of hospitalization (OR 0.56, 95% CI: 0.36 − 0.87)

Conclusions

In addition to individual factors such as comorbidity, other factors such as educational level, ethnicity or overcrowding were associated with hospitalization due to A (H1N1) 2009 influenza virus infections.

Keywords:
Influenza A (H1N1) 2009; Pandemic; Hospitalization; Social factors