Donchev, Deyan, Nikolova, Ralitsa, Vaseva, Katya et al. · Biomedicines · 2026 · DOI
Researchers compared gut bacteria in people with ME/CFS, long COVID, and healthy controls using stool samples. They observed that both ME/CFS and long COVID showed similar patterns of bacterial changes—including more of a bacterium called Sutterella and less of others—compared to healthy people, though the two conditions were not identical. The strongest links between bacterial patterns and symptoms were observed in fatigue and physical symptoms, though this is one study and findings require confirmation in larger follow-up research.
This study provides the first systematic comparative microbiome profiling in ME/CFS and long COVID within a single analytical framework, identifying both shared and disease-specific bacterial patterns. For ME/CFS patients, the findings may help clarify whether gut dysbiosis is a shared feature across post-infectious illnesses and whether particular bacterial signatures correlate with symptom domains—information relevant to future mechanistic and therapeutic research. However, the cross-sectional design limits conclusions about whether these bacterial patterns contribute to illness or simply reflect it.
This study does not establish that gut bacteria cause ME/CFS or long COVID symptoms; association does not imply causation in cross-sectional data. It does not determine whether observed bacterial changes are functionally relevant to disease pathology or merely correlative. It does not provide treatment recommendations or evidence that modifying the microbiome would improve outcomes. The findings are preliminary and require replication in larger, prospectively-followed cohorts with standardized case definitions.
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 →
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Primary citation
Donchev, Deyan, Nikolova, Ralitsa, Vaseva, Katya, Taskov, Hristo, Murdjeva, Mariana, Maes, Michael, et al. (2026). Comparative Gut Microbiome Alterations in Myalgic Encephalomyelitis/Chronic Fatigue Syndrome and Long COVID-19 Syndrome.. Biomedicines. https://doi.org/10.3390/biomedicines14061183
BibTeX
@article{mecfsatlas-donchev-2026-comparative-gut,
author = {Donchev, Deyan and Nikolova, Ralitsa and Vaseva, Katya and Taskov, Hristo and Murdjeva, Mariana and Maes, Michael and Ivanov, Ivan Nikolaev},
title = {Comparative Gut Microbiome Alterations in Myalgic Encephalomyelitis/Chronic Fatigue Syndrome and Long COVID-19 Syndrome.},
journal = {Biomedicines},
year = {2026},
doi = {10.3390/biomedicines14061183},
note = {PubMed: 42351611},
url = {https://www.mecfsatlas.com/evidence/donchev-2026-comparative-gut},
}Atlas snapshot reference
ME/CFS Atlas. Generator v1 / Scanner v1.4 / policy v0.1. Accessed 2026-07-08. https://www.mecfsatlas.com/evidence/donchev-2026-comparative-gut
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