1. National Influenza Centre, Department of Infectious, Parasitic and Immune-mediated Diseases, Istituto Superiore Sanità (ISS), Rome, Italy
2. Regional reference laboratory for Influenza, Department of Experimental and Clinical Medicine, University of Florence, Italy
3. Local health district (ASL 10), Florence, Italy
4. Infectious and Tropical Diseases Unit, Careggi Hospital, Florence, Italy
5. Infectious Diseases Unit, Careggi Hospital, Florence, Italy
6. Department of Health Sciences, University of Florence, Anna Meyer University Children's Hospital, Florence, Italy
7. Ministry of Health, Rome, Italy
8. Tuscany Regional Health Authority, Florence, Italy