[1] Inst Neuropathol, CH-8091 Zurich, Switzerland
[2] Natl Reference Ctr Prion Dis, CH-8091 Zurich, Switzerland
[3] Fed Off Publ Hlth, Div Epidemiol & Infect Dis, Bern, Switzerland
[4] Univ London Imperial Coll Sci Technol & Med, Fac Med, Dept Infect Dis Epidemiol, London, England
[5] Univ Zurich, Div Psychiat Res, Zurich, Switzerland