Valganciclovir is another antiviral similar to Valacyclovir which I reviewed in an earlier post.
According to PubMed:
- “Thirty CFS patients with elevated IgG antibody titers against HHV-6 and EBV… statistically significant differences in trajectories between groups were observed in MFI-20 mental fatigue subscore (P = 0.039), FSS score (P = 0.006), and cognitive function (P = 0.025)…patients experienced these improvements within the first 3 months and maintained that benefit over the remaining 9 months…Further investigation with longer treatment duration and a larger sample size is warranted”  – The term statistically significant (with P > 0.001) usually mean minor improvement.
- “Valganciclovir treatment, independent of the baseline antibody titers, was associated with self-rated improvement in physical and cognitive functioning for CFS patients who had positive HHV-6 and/or EBV serologies. Longer valganciclovir treatment correlated with an improved response.” 
- “Twelve patients with long-standing symptoms of central nervous system (CNS) dysfunction were found to have elevated antibody titres to human herpesvirus-6 (HHV-6) and Epstein-Barr virus (EBV)…Nine out of 12 (75%) patients experienced near resolution of their symptoms, allowing them all to return to the workforce or full time activites.”  Note: these patients did NOT have a Chronic Fatigue Diagnosis, just long term fatigue.
Only Impacts a small percentage of IBD/IBS patients
- “The prevalence of cytomegalovirus disease in our inflammatory bowel disease cohort (study group of 1023 people) was 1.37%.” 
- ” the prevalence of CMV infection was 22.7% in ulcerative colitis and 16.0% in Crohn’s disease… Immunuosuppressive therapy and age older than 30 years were identified as the main risk factors for the development of CMV infection in exacerbated IBD. ”  CMV does not cause IBS/CFS, rather IBS/CFS increases the odds of getting a CMV infection.
- “Most cases of cytomegalovirus (CMV) colitis that develop in patients with inflammatory bowel disease (IBD) are caused by reactivation of a latent virus.” 
- “The link between cytomegalovirus (CMV) infection and inflammatory bowel diseases remains an important subject of debate…Some treatments, notably steroids and cyclosporine A, have been shown to favor CMV reactivation, 
- [This is from the most recent study]”Multiple previous studies have sought evidence for ongoing, active infection with, or reactivation of, Herpesviruses in patients with chronic fatigue syndrome (CFS), with conflicting results….these did not differ between CFS cases and control patients…. data do not support the hypothesis of ongoing or reactivated EBV, HHV-6, or CMV infection in the pathogenesis of CFS. 
The theory of ongoing or reactivated EBV, HHV-6, or CMV infection in the pathogenesis of CFS has been abandoned by researchers since 2010. This theory continues to be circulated in many CFS support groups.
If a person with CFS happens to also have re-activation of a virus, that reactivation should be treated because such activation was reported to decreases the effectiveness of treatment with IBD. Reactivation will cause some symptoms to increase.
This drug should only be taken upon confirmation of active EBV, HHV-6, or CMV.