Elfaitouri, Amal, Shao, Xingwu, Mattsson Ulfstedt, Johan et al. · PloS one · 2011 · DOI
Researchers tested whether a virus called XMRV (xenotropic murine retrovirus) was present in Swedish patients with ME/CFS and fibromyalgia. Using sensitive tests on blood samples from 78 ME/CFS patients and 168 healthy blood donors, they found no evidence that this virus was present in any of the samples. This study helps answer questions about whether XMRV plays a role in ME/CFS.
XMRV was proposed as a potential pathogen in ME/CFS, generating significant hope and controversy. This rigorously controlled study from an independent laboratory in Sweden contributes to the broader scientific debate about XMRV's role in ME/CFS, helping researchers understand geographic variation in viral findings and informing future investigations.
This study does not prove that XMRV does not exist in any ME/CFS patients anywhere—it only shows absence in this Swedish cohort. It does not exclude the possibility that XMRV might be present in tissues other than blood, at very low levels, or in patients from other geographic regions. Negative PCR results cannot definitively rule out a pathogen's involvement in disease.
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
Elfaitouri, Amal, Shao, Xingwu, Mattsson Ulfstedt, Johan, Muradrasoli, Shaman, Bölin Wiener, Agnes, Golbob, Sultan, et al. (2011). Murine gammaretrovirus group G3 was not found in Swedish patients with myalgic encephalomyelitis/chronic fatigue syndrome and fibromyalgia.. PloS one. https://doi.org/10.1371/journal.pone.0024602
BibTeX
@article{mecfsatlas-elfaitouri-2011-murine-gammaretrovirus,
author = {Elfaitouri, Amal and Shao, Xingwu and Mattsson Ulfstedt, Johan and Muradrasoli, Shaman and Bölin Wiener, Agnes and Golbob, Sultan and Ohrmalm, Christina and Matousek, Michael and Zachrisson, Olof and Gottfries, Carl-Gerhard and Blomberg, Jonas},
title = {Murine gammaretrovirus group G3 was not found in Swedish patients with myalgic encephalomyelitis/chronic fatigue syndrome and fibromyalgia.},
journal = {PloS one},
year = {2011},
doi = {10.1371/journal.pone.0024602},
note = {PubMed: 22022360},
url = {https://www.mecfsatlas.com/evidence/elfaitouri-2011-murine-gammaretrovirus},
}Atlas snapshot reference
ME/CFS Atlas. Generator v1 / Scanner v1.4 / policy v0.1. Accessed 2026-05-28. https://www.mecfsatlas.com/evidence/elfaitouri-2011-murine-gammaretrovirus
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