1. Clinic of Infectious and Tropical Diseases, University of Modena and Reggio Emilia, Modena, Italy
2. Institute of Infectious and Tropical Diseases, University of Brescia, Brescia, Italy
3. National Institute for Infectious Diseases L Spallanzani, Rome, Italy
4. Department of Biomedical Sciences, University of Modena and Reggio Emilia, Modena, Italy