[1] Univ Exeter, Sch Med, Royal Cornwall Hosp Trust, Gastroenterol, Truro, England
[2] Univ Exeter, Sch Med, European Ctr Environm & Human Hlth, Truro, England
[3] Univ Med Ctr Rotterdam, Erasmus Med Ctr, Neurol, Rotterdam, Netherlands
[4] Radboud Univ Nijmegen, Med Ctr, Neurol, NL-6525 ED Nijmegen, Netherlands
[5] Jeroen Bosch Hosp, Neurol, Bilthoven, Netherlands
[6] Univ Med Ctr Rotterdam, Virosci, Rotterdam, Netherlands
[7] Univ Med Ctr Rotterdam, Erasmus Med Ctr, Immunol, Rotterdam, Netherlands
[8] Natl Inst Publ Hlth & Environm, Div Virol, Ctr Infect Dis Control, NL-3720 BA Bilthoven, Netherlands
[9] Royal Cornwall Hosp Trust, Microbiol, Truro, England
[10] Royal Cornwall Hosp Trust, Neurol, Truro, England