Davis, Hannah E, Assaf, Gina S, McCorkell, Lisa et al. · EClinicalMedicine · 2021 · DOI
This study surveyed nearly 3,800 people from around the world who had long-lasting COVID-19 symptoms lasting more than 28 days. By seven months after illness onset, most participants had not fully recovered and experienced an average of 56 symptoms affecting multiple body systems. The three most persistent symptoms were fatigue, post-exertional malaise (feeling worse after activity), and cognitive problems, with nearly 86% experiencing relapses triggered by exercise, physical activity, mental stress, or other exertion.
This large international study provides systematic characterization of long COVID's multisystem burden and its severe functional impact, demonstrating that ME/CFS-like features—particularly post-exertional malaise and cognitive dysfunction—persist across months. For ME/CFS patients, this highlights overlapping pathophysiology and validates experiences of prolonged disability and activity-dependent symptom exacerbation that are often underrecognized in standard medical practice.
This study does not establish causality or the biological mechanisms underlying long COVID symptoms. The cross-sectional design cannot determine whether symptoms follow distinct disease stages or whether recovery patterns differ by biological subgroup. The reliance on online surveys of self-selected participants from support groups may overestimate symptom burden and disability compared to the broader population of people with prolonged COVID.
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
Davis, Hannah E, Assaf, Gina S, McCorkell, Lisa, Wei, Hannah, Low, Ryan J, Re'em, Yochai, et al. (2021). Characterizing long COVID in an international cohort: 7 months of symptoms and their impact.. EClinicalMedicine. https://doi.org/10.1016/j.eclinm.2021.101019
BibTeX
@article{mecfsatlas-davis-2021-characterizing-long,
author = {Davis, Hannah E and Assaf, Gina S and McCorkell, Lisa and Wei, Hannah and Low, Ryan J and Re'em, Yochai and Redfield, Signe and Austin, Jared P and Akrami, Athena},
title = {Characterizing long COVID in an international cohort: 7 months of symptoms and their impact.},
journal = {EClinicalMedicine},
year = {2021},
doi = {10.1016/j.eclinm.2021.101019},
note = {PubMed: 34308300},
url = {https://www.mecfsatlas.com/evidence/davis-2021-characterizing-long},
}Atlas snapshot reference
ME/CFS Atlas. Generator v1 / Scanner v1.4 / policy v0.1. Accessed 2026-05-28. https://www.mecfsatlas.com/evidence/davis-2021-characterizing-long
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