6 Infectious Diseases Unit, Vita-Salute San Raffaele University, Milan, Italy; Infectious Diseases Unit, San Raffaele Scientific Institute, Milan, Italy.
7 Infectious Diseases Unit, San Raffaele Scientific Institute, Milan, Italy.
8 Laboratory of Clinical Microbiology, Virology and Bioemergencies, "Luigi Sacco" Hospital, ASST Fatebenefratelli Sacco, Via G.B. Grassi 74, Milan 20157, Italy; Department of Biomedical and Clinical Sciences "Luigi Sacco", University of Milan, Milan, Italy.