1. Department of Experimental and Clinical Medicine, University of Florence, Florence, Italy
2. Infectious and Tropical Diseases Unit, Careggi University and Hospital, Florence, Italy
3. Institute of Clinical Infectious Diseases, Catholic University of Sacred Heart, Policlinico Gemelli, Rome, Italy
4. Unit of Virology and Molecular Microbiology, University Hospital, Modena, Italy
5. Department of Infectious Diseases, University of Modena, Modena, Italy
6. Department of Biomedical Sciences and Human Oncology, Clinic of Infectious Diseases, University of Bari, Italy
7. Clinic of Immunology and Internal Medicine, Ospedale Policlinico San Martino, Genoa, Italy
8. Microbiology and Virology Laboratory, L. Sacco Hospital, Milano, Italy
9. Virology Unit, Azienda Ospedaliera Universitaria Ospedali Riuniti di Ancona, Ancona, Italy
10. Immuno-Ematology and Transfusion Medicine Service, Cremona Hospital, Cremona, Italy
11. Infectious Diseases, San Paolo Hospital, Milan, Italy