We studied 3231 patients with acute central nervous system (CNS) symptoms of suspected viral origin to elucidate the current etiologic spectrum. In 46% of the cases, a viral finding was observed. Varicella-zoster virus (VZV) was the main agent associated with encephalitis, as well as meningitis and myelitis. VZV comprised 29% of all confirmed or probable etiologic agents. Herpes simplex virus (HSV) and enteroviruses accounted 11% each, and influenza A virus 7%. VZV seems to have achieved a major role in viral infections of CNS. In encephalitis in our population, VZV is clearly more commonly associated with these neurological diseases than HSV. The increase in VZV findings may in part be a pseudophenomenon due to improved diagnostic methods, however, a true increase may have occurred and the pathogenetic mechanisms behind this should be elucidated.

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A diagnosis of posttransplantation human herpesvirus-6 (HHV-6) infection was established for eight adult recipients among a liver transplantation patient population of 121. The diagnosis was based on serology and demonstration of HHV-6 specific antigens in liver biopsy specimens with use of monoclonal antibodies and immunoperoxidase staining. A significant graft dysfunction was recorded in association with serodiagnosis. HHV-6 early antigens, as well as HHV-6 variant B antigens, were detected retrospectively in all six available liver biopsy specimens. Histologic examination of biopsy specimens demonstrated acute rejection in 5 of the 8 patients, and 3 patients had portal lymphocyte infiltration. In five cases cytomegalovirus (CMV) infection was associated with HHV-6 infection; in four cases CMV antigens were also detected in the biopsy specimens. Two patients who had pure HHV-6 infection without CMV infection or rejection had significantly impaired graft function, with a positive antigen-detection test. Thus, HHV-6 may infect the liver allograft and cause graft dysfunction and may possibly be associated with rejection and/or CMV infection.