Naess, Halvor, Sundal, Endre, Myhr, Kjell-Morten et al. · In vivo (Athens, Greece) · 2010
This study looked at 873 ME/CFS patients in Norway to see whether their illness started after an infection. About 77% of patients reported having an infection before their fatigue began. Patients who had an infection at the start were more likely to have a sudden onset of fatigue and to show some improvement by the time they were seen at the clinic, compared to those without an infection.
Understanding whether ME/CFS symptoms differ based on initial infectious trigger may help identify disease subtypes and guide clinical management. This study provides data on the frequency and characteristics of postinfectious presentations in a substantial tertiary cohort, supporting the recognition that infection-triggered ME/CFS may represent a distinct phenotype with potentially better prognosis.
This study does not establish that infection causes ME/CFS—only that infection preceding symptom onset is common and associated with certain symptom patterns. The lack of antibody differences between groups does not rule out infectious etiology and may reflect limitations in serological detection. The observational design cannot determine causality or why some patients improve while others do not.
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
Naess, Halvor, Sundal, Endre, Myhr, Kjell-Morten, & Nyland, Harald Inge (2010). Postinfectious and chronic fatigue syndromes: clinical experience from a tertiary-referral centre in Norway.. In vivo (Athens, Greece). https://pubmed.ncbi.nlm.nih.gov/20363992/
BibTeX
@article{mecfsatlas-naess-2010-postinfectious-chronic,
author = {Naess, Halvor and Sundal, Endre and Myhr, Kjell-Morten and Nyland, Harald Inge},
title = {Postinfectious and chronic fatigue syndromes: clinical experience from a tertiary-referral centre in Norway.},
journal = {In vivo (Athens, Greece)},
year = {2010},
note = {PubMed: 20363992},
url = {https://www.mecfsatlas.com/evidence/naess-2010-postinfectious-chronic},
}Atlas snapshot reference
ME/CFS Atlas. Generator v1 / Scanner v1.4 / policy v0.1. Accessed 2026-05-26. https://www.mecfsatlas.com/evidence/naess-2010-postinfectious-chronic
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