1. Hygiene Section, Department of Internal Medicine and Public Health, School of Medicine, University of Bari, Bari, Italy.
2. Gastroenterology Unit, “Riuniti” Hospital, Foggia, Italy.
3. Dipartimento di Malattie Infettive, Parassitarie e Immunomediate, Istituto Superiore di Sanità, Rome, Italy.