Studies on the relationship between chronic fatigue syndrome and Epstein-Barr virus in Japan.

Among 1,153 consecutive patients, 22 patients (1.9%) who complained of chronic fatigue for a period of over 6 months without detectable causes were studied. Ten patients (0.86%) satisfied the criteria of chronic fatigue syndrome (CFS) and were classified to be definite cases of CFS. The other patients were classified as probable cases. In order to clarify the role of Epstein-Barr virus (EBV) as a cause of CFS, we measured various antibodies for EBV. The definite cases had significantly higher titers of early antigen complex (EA)-IgG than both the probable cases and controls. We proposed the EA-IgG/EBNA ratio as the indicator of activation of EBV and attempted to estimate the degree of fatigue by the EA-IgG/EBNA ratio. The highest ratio value (16.0) of the 22 patients ratios was the most serious case. In general, the ratio correlated with the degree of fatigue. Based on these results, it was concluded that a relationship does exist between CFS and EBV.