[1] SWEDISH INST INFECT DIS CONTROL,DEPT VIROL,S-10521 STOCKHOLM,SWEDEN
[2] HUDDINGE UNIV HOSP,INST IMMUNOL MICROBIOL PATHOL & INFECT DIS,S-14186 HUDDINGE,SWEDEN
[3] HUDDINGE UNIV HOSP,DEPT CLIN NEUROSCI & FAMILY MED,S-14186 HUDDINGE,SWEDEN
[4] UMEA UNIV HOSP,DEPT NEUROSURG,S-90185 UMEA,SWEDEN