Chronic fatigue syndrome. A critical appraisal of the role of Epstein-Barr virus.

The symptom complex currently designated the chronic fatigue syndrome was previously termed the chronic or chronic active Epstein-Barr virus syndrome or the chronic mononucleosis syndrome, prematurely assuming an etiologic role for the Epstein-Barr virus (EBV). This presumption derived from the fact that some patients with the chronic fatigue syndrome have very high or very low titers of certain antibodies to EBV. A review of seroepidemiologic patterns of response to EBV and of studies of patients with the chronic fatigue syndrome shows that these antibody titers overlap considerably both with those of controls or other healthy persons and with those of patients with other illnesses. Given the high prevalence of exposure to EBV, it would be difficult to determine whether the virus caused the syndrome or whether the antibody elevations resulted from the illness, even if distinct differences in titers existed. Other methodologic issues of control selection, laboratory test comparability, and differing case definitions pose problems in studying this syndrome. The recently published working case definition should facilitate the continuing search for causes.