[Chronic fatigue syndrome and virus infection: human herpesvirus 6 (HHV-6) infection]

Chronic fatigue syndrome (CFS) is newly-recognized disease characterized by chronic and debilitating fatigue. It has been suggested that viral infection may be involved in this syndrome from the results of clinical examination, including increased activity of 2',5'-synthetase in leukocytes of patients. The following viruses have been reported as etiologic agents of this disease. First, many studies have found elevated levels of IgG to viral capsid antigen and early antigens to Epstein-Barr virus (EBV), but low titer or absence of antibody to EBV-associated nuclear antigen. Second, the enteroviruses have also been implicated as possible causative agent of CFS, because virus could be isolated from patients. Recently it was also reported that antibodies to human T-lymphotropic virus (HTLV) and HTLV type II (HTLV-II) gag sequence were detectable in patients. Finally several reports state that human herpesvirus 6 (HHV-6) could be isolated from CFS patients in the high frequency. In conclusion, it is still early to identify the etiologic agent from these reports, and more effort is needed.