Steffen, Imke, Tyrrell, D Lorne, Stein, Eleanor et al. · PloS one · 2011 · DOI
Researchers tested blood samples from 58 Canadian ME/CFS patients and 57 healthy people to look for two viruses (XMRV and MLV) that had been suggested as possible causes of ME/CFS. Using multiple sensitive tests, they found no trace of these viruses or antibodies against them in any of the samples. This study challenges earlier reports that had linked these viruses to ME/CFS.
This study is important because it provided critical evidence against the XMRV hypothesis for ME/CFS during a period when this association was being actively investigated as a potential disease mechanism. The rigorous negative findings helped redirect research toward other biological mechanisms and highlighted the importance of independent replication in ME/CFS research. It emphasizes the need for methodological standardization and reproducibility in identifying pathogens associated with ME/CFS.
This study does not prove that no retrovirus is involved in ME/CFS—only that these specific gammaretroviruses (XMRV and MLV) were not detected in this Canadian population. The negative findings do not establish what the actual viral or infectious cause of ME/CFS might be. Geographic or temporal variation in pathogen prevalence could mean different results in other populations or time periods.
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
Steffen, Imke, Tyrrell, D Lorne, Stein, Eleanor, Montalvo, Leilani, Lee, Tzong-Hae, Zhou, Yanchen, et al. (2011). No evidence for XMRV nucleic acids, infectious virus or anti-XMRV antibodies in Canadian patients with chronic fatigue syndrome.. PloS one. https://doi.org/10.1371/journal.pone.0027870
BibTeX
@article{mecfsatlas-steffen-2011-evidence-xmrv,
author = {Steffen, Imke and Tyrrell, D Lorne and Stein, Eleanor and Montalvo, Leilani and Lee, Tzong-Hae and Zhou, Yanchen and Lu, Kai and Switzer, William M and Tang, Shaohua and Jia, Hongwei and Hockman, Darren and Santer, Deanna M and Logan, Michael and Landi, Amir and Law, John and Houghton, Michael and Simmons, Graham},
title = {No evidence for XMRV nucleic acids, infectious virus or anti-XMRV antibodies in Canadian patients with chronic fatigue syndrome.},
journal = {PloS one},
year = {2011},
doi = {10.1371/journal.pone.0027870},
note = {PubMed: 22114717},
url = {https://www.mecfsatlas.com/evidence/steffen-2011-evidence-xmrv},
}Atlas snapshot reference
ME/CFS Atlas. Generator v1 / Scanner v1.4 / policy v0.1. Accessed 2026-05-30. https://www.mecfsatlas.com/evidence/steffen-2011-evidence-xmrv
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