1. Department of Clinical Sciences and Community Health, University of Milan, Milan, Italy;
2. Department of Obstetrics, Gynecology, and Neonatology, University of Milan, Fondazione IRCCS Ca’ Granda Ospedale Maggiore Policlinico, Milan, Italy;
3. Clinical and Evaluative Epidemiology Department, Trento Health Service, Trento, Italy;
4. O.U. Microbiology and Virology, Trento Health Service, Trento, Italy