[1] Ist Super Sanita, Dept Infect Parasit & Immune mediated Dis, I-00161 Rome, Italy
[2] Univ Siena, Dept Med Biotechnol, I-53100 Siena, Italy
[3] Ist Super Sanita, Natl Ctr Epidemiol Surveillance & Hlth Promot, I-00161 Rome, Italy
[4] Univ Florence, Dept Expt & Clin Med, Florence, Italy
[5] Careggi Univ Hosp, Dept Lab Med, Clin Microbiol & Virol Unit, Florence, Italy