For years the controversary over whether or not EBV was the cause or related to CFS has continued to be researched.
Back in 2006. a clinical study showed that 100% of the patients studied (58) had evidence of prior EBV exposure and 72% had evidence for reactivated EBV infection. The study also showed that 94% of the patients studies had B-cell immunodeficiency with a marked depletion of their CD19+IgM+ mature B-lymphocyte population.
The study also found that 81% of the CFS patients in the study experienced some improvement of their symptoms once they were treated with folinic acid.
So the initial theory that there is a high incidence of severe B-cell immunodeficiency and chronic reactivated Epstein-Barr virus (EBV) infection in patients with CFS was found to be correct.