Montoya, Jose G, Kogelnik, Andreas M, Bhangoo, Munveer et al. · Journal of medical virology · 2013 · DOI
This study tested whether a antiviral medication called valganciclovir could help ME/CFS patients who had evidence of past infection with two common viruses (HHV-6 and EBV). Thirty patients received either the medication or placebo for 6 months. Those taking valganciclovir showed improvements in mental fatigue, overall fatigue, and cognitive function within the first 3 months, and these improvements lasted through the end of the study. The medication also produced changes in immune cell counts that suggest the patient's immune system was shifting toward a different state.
This is one of the few randomized controlled trials testing a pathogen-directed treatment in ME/CFS, addressing the hypothesis that reactivated herpesviruses may contribute to symptoms in a subset of patients. If confirmed in larger studies, valganciclovir or similar antivirals could become the first evidence-based pharmaceutical option for certain ME/CFS patients, potentially transforming clinical management.
This study does not establish that HHV-6 or EBV reactivation causes ME/CFS, only that reducing viral burden may help some patients with elevated antibody titers. The small sample size (n=30) and lack of statistical significance on the primary endpoint (MFI-20 total score) limit generalizability. The unchanged viral IgG titers suggest the mechanism may not be simple viral suppression, leaving the true biological mechanism unclear.
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
Montoya, Jose G, Kogelnik, Andreas M, Bhangoo, Munveer, Lunn, Mitchell R, Flamand, Louis, Merrihew, Lindsey E, et al. (2013). Randomized clinical trial to evaluate the efficacy and safety of valganciclovir in a subset of patients with chronic fatigue syndrome.. Journal of medical virology. https://doi.org/10.1002/jmv.23713
BibTeX
@article{mecfsatlas-montoya-2013-randomized-clinical,
author = {Montoya, Jose G and Kogelnik, Andreas M and Bhangoo, Munveer and Lunn, Mitchell R and Flamand, Louis and Merrihew, Lindsey E and Watt, Tessa and Kubo, Jessica T and Paik, Jane and Desai, Manisha},
title = {Randomized clinical trial to evaluate the efficacy and safety of valganciclovir in a subset of patients with chronic fatigue syndrome.},
journal = {Journal of medical virology},
year = {2013},
doi = {10.1002/jmv.23713},
note = {PubMed: 23959519},
url = {https://www.mecfsatlas.com/evidence/montoya-2013-randomized-clinical},
}Atlas snapshot reference
ME/CFS Atlas. Generator v1 / Scanner v1.4 / policy v0.1. Accessed 2026-05-30. https://www.mecfsatlas.com/evidence/montoya-2013-randomized-clinical
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