Social factors related to the clinical severity of influenza cases in Spain during the A (H1N1) 2009 virus pandemic
José María Mayoral*, Jordi Alonso, Olatz Garín, Zaida Herrador, Jenaro Astray, Maretva Baricot, Jesús Castilla, Rafael Cantón, Ady Castro, Miguel Delgado-Rodríguez, Alicia Ferri, Pere Godoy, Fernando Gónzález-Candelas, Vicente Martín, Tomás Pumarola, José María Quintana, Núria Soldevila, Sonia Tamames, Ángela Domínguez and and the CIBERESP Cases and Controls in Pandemic Influenza Working Group, Spain