1. Clinic of Infectious Diseases, University of Bari, Bari, Italy.
2. Department of Internal Medicine and Public Health, Hygiene Section, Policlinico, University of Bari, Bari, Italy.
3. Dip. di Malattie Infettive, Parassitarie ed Immunomediate, Istituto Superiore di Sanità, Roma, Italy.