Prevalence of IgM antibodies to human herpesvirus 6 early antigen (p41/38) in patients with chronic fatigue syndrome.

To evaluate the association between human herpesvirus 6 (HHV-6) and chronic fatigue syndrome (CFS), 2 geographically separate groups of CFS patients (125 and 29 patients, respectively) and healthy controls (150 and 15 controls, respectively) were compared, using an EIA, for antibodies to HHV-6 early antigen p41/38 (EA). Sixty percent (93/154) of CFS patients were were positive for HHV-6 EA IgM, 40% (61/154) were positive for IgG, and 23% (35/154) were positive for both. A total of 119 (77%) of the CFS patients were positive for HHV-6 EA IgG or IgM (or both); only 12% (20/165) of the controls had IgG or IgM to HHV-6 EA. These data demonstrate that more CFS patients than controls had elevated levels of HHV-6 EA-specific IgM, perhaps indicating active replication of HHV-6 in CFS.