Zhang, Q W, Natelson, B H, Ottenweller, J E et al. · Chronobiology international · 2000 · DOI
This study looked at 69 people with severe ME/CFS who all experienced a sudden onset of illness, with symptoms like sore throat, extreme fatigue, and body aches developing within 2 days. Researchers found that these sudden onsets happened much more often during winter months (November through January) and least often in spring (April through May). This pattern suggests that ME/CFS may be triggered by an infectious agent rather than being purely psychological.
This study provides evidence that the sudden, infectious-like onset experienced by many ME/CFS patients may have a biological basis rather than a psychological one. The seasonal pattern observed could help guide future research into environmental triggers or seasonal infections that may initiate ME/CFS, potentially leading to better prevention or early intervention strategies.
This study does not prove that a specific infectious agent causes ME/CFS, nor does it identify which pathogen might be responsible. The seasonal pattern, while suggestive of infectious etiology, could also reflect seasonal variation in other factors (environmental exposures, immune function, vitamin D levels) and does not establish causation. Additionally, the findings apply only to severely affected patients with sudden onset and may not generalize to all ME/CFS presentations.
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
Zhang, Q W, Natelson, B H, Ottenweller, J E, Servatius, R J, Nelson, J J, De Luca, J, et al. (2000). Chronic fatigue syndrome beginning suddenly occurs seasonally over the year.. Chronobiology international. https://doi.org/10.1081/cbi-100101035
BibTeX
@article{mecfsatlas-zhang-2000-chronic-fatigue,
author = {Zhang, Q W and Natelson, B H and Ottenweller, J E and Servatius, R J and Nelson, J J and De Luca, J and Tiersky, L and Lange, G},
title = {Chronic fatigue syndrome beginning suddenly occurs seasonally over the year.},
journal = {Chronobiology international},
year = {2000},
doi = {10.1081/cbi-100101035},
note = {PubMed: 10672437},
url = {https://www.mecfsatlas.com/evidence/zhang-2000-chronic-fatigue},
}Atlas snapshot reference
ME/CFS Atlas. Generator v1 / Scanner v1.4 / policy v0.1. Accessed 2026-05-26. https://www.mecfsatlas.com/evidence/zhang-2000-chronic-fatigue
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