1. Department of Preventive Medicine, Hospital Universitario Puerta de Hierro. Madrid, Spain
2. Department of Preventive Medicine, Hospital Vall d´Hebron. Barcelona, Spain
3. Department of Preventive Medicine, Hospital Carlos Haya. Málaga, Spain
4. Department of Preventive Medicine and Public Health, University of Santiago de Compostela, Spain
5. Department of Preventive Medicine, Hospital Universitario Puerto del Mar, Cádiz, Spain
6. Epidemiologi Unit. Hospital Clinic. Barcelona, Spain
7. Department of Microbiology. Hospital Universitario Ramón y Cajal. Madrid, Spain