Shen, Yanhan, Shahn, Zach, Robertson, McKaylee M et al. · BMC infectious diseases · 2026 · DOI
This study followed over 500 people with long COVID for up to a year, tracking their symptoms over time. Researchers identified three groups based on symptom burden: one with persistent severe symptoms (including fatigue, brain fog, post-exertional malaise, and pain), one with moderate symptoms that improved, and one with minimal symptoms. The findings are preliminary and based on self-reported data, so the stability and generalisability of these groups to other long COVID populations remain to be confirmed.
By analogy, this study's longitudinal clustering approach and identification of symptom phenotypes may inform ME/CFS research, where heterogeneity and variable disease trajectories similarly complicate classification and clinical management. The association of mental health disorder and immunodeficiency with higher symptom burden in long COVID could prompt similar investigation in ME/CFS cohorts to support risk stratification and tailored intervention design.
This study does not establish causal relationships between demographic factors and symptom burden—only associations observed in one cohort. It does not prove that the identified clusters represent biologically distinct disease entities, nor does it demonstrate that cluster membership predicts treatment response or long-term outcomes. The relevance of long COVID clustering to ME/CFS aetiology and phenotyping remains unclear and requires direct ME/CFS validation.
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
Shen, Yanhan, Shahn, Zach, Robertson, McKaylee M, Gebo, Kelly, & Nash, Denis (2026). Long COVID longitudinal symptoms burden clusters within a national community-based cohort.. BMC infectious diseases. https://doi.org/10.1186/s12879-026-13590-2
BibTeX
@article{mecfsatlas-shen-2026-long-covid,
author = {Shen, Yanhan and Shahn, Zach and Robertson, McKaylee M and Gebo, Kelly and Nash, Denis},
title = {Long COVID longitudinal symptoms burden clusters within a national community-based cohort.},
journal = {BMC infectious diseases},
year = {2026},
doi = {10.1186/s12879-026-13590-2},
note = {PubMed: 42168930},
url = {https://www.mecfsatlas.com/evidence/shen-2026-long-covid},
}Atlas snapshot reference
ME/CFS Atlas. Generator v1 / Scanner v1.4 / policy v0.1. Accessed 2026-05-27. https://www.mecfsatlas.com/evidence/shen-2026-long-covid
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