[Viral infection and its causative role for chronic fatigue syndrome]

Patients with chronic fatigue syndrome (CFS), of unknown etiology, have been increasingly reported. This syndrome is characterized by debilitating fatigue, lymphadenopathy, and fever. Herein, I focus on and review this syndrome from the view point of the causative role of viral infection. Since the symptoms of CFS are similar to those of chronic infectious mononucleosis (CIM) or chronic Epstein-Barr virus infection (CEBV), the role of EBV has been intensively studied. The etiological relationship between EBV and CFS, however, is questioned, like other lymphotropic viruses, including human retroviruses, adenoviruses and human herpesvirus 6. Additionally, severe chronic active EBV infection syndrome (SCAEBV) is also discussed in this review because symptoms of this disorder are similar to those of CFS but more severe in degree. Currently, the cause(s) and treatment of CFS are enigmatic and require further research and multidisciplinary study.