Ducret, Diane, Mijatovic, Tatjana · Viruses · 2026 · DOI
A retrospective study observed that patients with neurological or neuropsychiatric symptoms after COVID-19 had a substantially higher frequency of HHV-7 (a type of herpesvirus) detected in testing compared to pre-COVID reference data. The study involved 30 long COVID patients, of whom 77% tested positive for HHV-7, compared to 29% in historical controls. The authors note that these are early findings in a small patient group and call for prospective studies to investigate whether HHV-7 plays a role in long COVID neurological symptoms.
By analogy, this finding may be relevant to ME/CFS research, since a subset of ME/CFS patients have post-infectious onset and some studies have explored herpesvirus reactivation in ME/CFS. However, the study examined long COVID specifically, and relevance to ME/CFS remains unclear without direct investigation. The observation of high HHV-7 frequency in a neuropsychiatric long COVID phenotype could prompt parallel inquiry into whether HHV-7 or related herpesviruses are associated with similar neurological phenotypes in ME/CFS.
This study does not establish that HHV-7 reactivation causes neurological or neuropsychiatric long COVID symptoms; it identifies an association in a small, retrospectively selected cohort. It does not prove HHV-7 is a mechanism of long COVID pathology, nor does it generalise to all long COVID patients or to ME/CFS. The cross-sectional and retrospective design precludes causal inference, and the single longitudinal case does not establish a functional relationship between viral load and symptom severity.
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
Ducret, Diane & Mijatovic, Tatjana (2026). High Frequency of HHV-7 Reactivation in Neurological and Neuropsychiatric Long COVID: A Retrospective Observational Study.. Viruses. https://doi.org/10.3390/v18091043
BibTeX
@article{mecfsatlas-ducret-2026-high-frequency,
author = {Ducret, Diane and Mijatovic, Tatjana},
title = {High Frequency of HHV-7 Reactivation in Neurological and Neuropsychiatric Long COVID: A Retrospective Observational Study.},
journal = {Viruses},
year = {2026},
doi = {10.3390/v18091043},
note = {PubMed: 42797874},
url = {https://www.mecfsatlas.com/evidence/ducret-2026-high-frequency},
}Atlas snapshot reference
ME/CFS Atlas. Generator v1 / Scanner v1.4 / policy v0.1. Accessed 2026-09-26. https://www.mecfsatlas.com/evidence/ducret-2026-high-frequency
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