Watt, Tessa, Oberfoell, Stephanie, Balise, Raymond et al. · Journal of medical virology · 2012 · DOI
This study looked at whether a antiviral medication called valganciclovir could help ME/CFS patients who had high levels of antibodies to two common viruses: HHV-6 and EBV. Sixty-one patients took the medication for varying lengths of time, and about half reported at least 30% improvement in their physical energy and thinking abilities. Interestingly, the improvement didn't depend on how high their antibody levels were at the start—patients improved simply from taking the medication, and those who took it longer did better.
This study provides preliminary evidence that some ME/CFS patients with evidence of chronic HHV-6/EBV infection may benefit from antiviral treatment, independent of antibody titer levels. The finding that longer treatment duration associates with better outcomes could inform treatment planning for patients considering this intervention.
This observational study cannot establish that valganciclovir causally improves ME/CFS symptoms—the lack of a control group means improvements could reflect placebo effect, natural recovery, or other unmeasured factors. It does not prove that HHV-6 or EBV causes ME/CFS, only that some patients with these serologies report symptom improvement with treatment. The study cannot determine optimal dosing, duration, or which patients are most likely to respond.
About the PEM badge: “PEM required” means post-exertional malaise was an explicit required diagnostic criterion for participant inclusion in this study — not that PEM was studied, observed, or discussed. Studies using criteria that do not require PEM (e.g. Fukuda, Oxford) are tagged “PEM not required”. How the atlas works →
The first block is for the primary paper and is the citation you should use in research work. The atlas-snapshot line only applies if you are specifically referring to this atlas’s reading of the paper on the date shown.
Primary citation
Watt, Tessa, Oberfoell, Stephanie, Balise, Raymond, Lunn, Mitchell R, Kar, Aroop K, Merrihew, Lindsey, et al. (2012). Response to valganciclovir in chronic fatigue syndrome patients with human herpesvirus 6 and Epstein-Barr virus IgG antibody titers.. Journal of medical virology. https://doi.org/10.1002/jmv.23411
BibTeX
@article{mecfsatlas-watt-2012-response-valganciclovir,
author = {Watt, Tessa and Oberfoell, Stephanie and Balise, Raymond and Lunn, Mitchell R and Kar, Aroop K and Merrihew, Lindsey and Bhangoo, Munveer S and Montoya, José G},
title = {Response to valganciclovir in chronic fatigue syndrome patients with human herpesvirus 6 and Epstein-Barr virus IgG antibody titers.},
journal = {Journal of medical virology},
year = {2012},
doi = {10.1002/jmv.23411},
note = {PubMed: 23080504},
url = {https://www.mecfsatlas.com/evidence/watt-2012-response-valganciclovir},
}Atlas snapshot reference
ME/CFS Atlas. Generator v1 / Scanner v1.4 / policy v0.1. Accessed 2026-05-26. https://www.mecfsatlas.com/evidence/watt-2012-response-valganciclovir
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