Katz, Ben Z, Shiraishi, Yukiko, Mears, Cynthia J et al. · Pediatrics · 2009 · DOI
This study followed 301 teenagers with infectious mononucleosis (mono) to see how many developed ME/CFS afterward. Researchers checked in at 6, 12, and 24 months and found that fewer teenagers had ME/CFS as time went on: 13% at 6 months, 7% at 12 months, and 4% at 24 months. All 13 teenagers still diagnosed with ME/CFS at 24 months were female, and they had reported more severe fatigue earlier in their illness.
This study provides important longitudinal evidence that infectious mononucleosis can trigger ME/CFS in adolescents, establishing post-infectious onset as a documented pathway to the disease. The finding that most cases resolve over two years, combined with identification of female sex and higher early fatigue severity as risk factors, offers clues to disease mechanisms and may help clinicians identify patients at higher risk for persistent symptoms.
This study does not prove that mono causes ME/CFS in all cases, only that it may be a trigger in some adolescents. The study cannot explain why females were exclusively affected in the 24-month group or identify the underlying biological mechanisms. Additionally, correlation between greater fatigue severity at 12 months and persistent ME/CFS does not establish whether early fatigue severity itself predicts poor recovery or is simply a marker of disease 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 →
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
Katz, Ben Z, Shiraishi, Yukiko, Mears, Cynthia J, Binns, Helen J, & Taylor, Renee (2009). Chronic fatigue syndrome after infectious mononucleosis in adolescents.. Pediatrics. https://doi.org/10.1542/peds.2008-1879
BibTeX
@article{mecfsatlas-katz-2009-chronic-fatigue,
author = {Katz, Ben Z and Shiraishi, Yukiko and Mears, Cynthia J and Binns, Helen J and Taylor, Renee},
title = {Chronic fatigue syndrome after infectious mononucleosis in adolescents.},
journal = {Pediatrics},
year = {2009},
doi = {10.1542/peds.2008-1879},
note = {PubMed: 19564299},
url = {https://www.mecfsatlas.com/evidence/katz-2009-chronic-fatigue},
}Atlas snapshot reference
ME/CFS Atlas. Generator v1 / Scanner v1.4 / policy v0.1. Accessed 2026-05-28. https://www.mecfsatlas.com/evidence/katz-2009-chronic-fatigue
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