1. Department of Histology, Microbiology and Medical Biotechnology, Padova University, Padova
2. Center of Preventive Medicine and HIV Outpatient Clinic, Verona
3. Infectious Diseases Unit, Schio Hospital, Schio
4. Infectious Diseases Unit, Vicenza Hospital, Vicenza
5. Infectious Diseases Unit, Padova Hospital, Padova
6. Infectious Diseases Unit, Treviso Hospital, Treviso
7. Department of Molecular Biology, University of Siena, Siena
8. Department of Public Health, University of Roma Tor Vergata, Rome, Italy