1. Nephrology and Dialysis Unit, University Hospital ‘Maggiore della Carità’, Novara, Italy
2. Unit of Nephrology and Hemodialysis, IRCCS Fondazione Salvatore Maugeri, University of Pavia, Pavia, Italy
3. Microbiology and Virology Laboratory, University Hospital ‘Maggiore della Carità’, Novara, Italy