Branco, J C, Tavares, V, Abreu, I et al. · Acta medica portuguesa · 1994
This study looked at whether a common virus called parvovirus B19 might be responsible for fibromyalgia, a condition similar to ME/CFS that causes widespread pain and fatigue. Researchers compared blood antibodies (which show past infection) in 52 fibromyalgia patients versus 39 healthy people. They found slightly higher rates of past parvovirus infection in fibromyalgia patients, but the difference was too small to be meaningful, so they concluded the virus is probably not the cause of fibromyalgia.
Since ME/CFS and fibromyalgia share overlapping features and both have been studied in relation to viral triggers, determining whether viral infections drive these conditions is clinically important. Clarifying the role of specific viruses like parvovirus B19 helps distinguish true infectious causes from coincidental or secondary associations, which has implications for diagnosis and treatment.
This study does not prove parvovirus B19 plays no role in fibromyalgia; non-significant results do not equal negative results, and a small sample may lack statistical power. It also does not address whether active viral replication (rather than past infection marked by IgG) might be relevant, nor does it clarify the mechanistic link between any viral infection and fibromyalgia or ME/CFS symptom onset.
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
Branco, J C, Tavares, V, Abreu, I, & Humbel, R L (1994). [Viral infection and fibromyalgia].. Acta medica portuguesa. https://pubmed.ncbi.nlm.nih.gov/7942134/
BibTeX
@article{mecfsatlas-branco-1994-viral-infection,
author = {Branco, J C and Tavares, V and Abreu, I and Humbel, R L},
title = {[Viral infection and fibromyalgia].},
journal = {Acta medica portuguesa},
year = {1994},
note = {PubMed: 7942134},
url = {https://www.mecfsatlas.com/evidence/branco-1994-viral-infection},
}Atlas snapshot reference
ME/CFS Atlas. Generator v1 / Scanner v1.4 / policy v0.1. Accessed 2026-05-30. https://www.mecfsatlas.com/evidence/branco-1994-viral-infection
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