[1] San Raffaele Sci Inst, Dept Infect Dis, I-20132 Milan, Italy
[2] Univ Milan, L Sacco Hosp, Dept Pathol, Milan, Italy
[3] Santa Maria Nuova Hosp, Dept Infect Dis, Reggio Emilia, Italy
[4] Univ Hamburg, Acad Teaching Hosp, Marienkrankenhaus, Dept Neurol, Hamburg, Germany
[5] Karolinska Inst, Swedish Inst Infect Dis Control, Dept Virol, Stockholm, Sweden
[6] Karolinska Inst, MTC, Stockholm, Sweden