Myalgic encephalomyelitis/chronic fatigue syndrome (ME/CFS) is a complex and debilitating condition that shares clinical features with other chronic conditions.
What is ME/CFS?
ME/CFS is a complex and debilitating condition, characterised by:
- profound fatigue following exertion (not relieved by sleep or rest)
- unrefreshing sleep
- cognitive impairment
- post exertional malaise (PEM) is suggested as a cardinal feature of ME/CFS.1,2
The cause of ME/CFS is not fully known, but many theories exist.3 There is no diagnostic test and no universally accepted diagnostic criteria or case definition for ME/CFS, which can make a definitive diagnosis difficult.4 Diagnosis currently relies on elimination of other similar disease patterns and self-reported symptom based criteria.
Related conditions
ME/CFS shares many clinical features with other chronic conditions, including Long COVID (also known as post-acute sequalae of COVID-19 or PASC), postural orthostatic tachycardia syndrome (or POTS) and fibromyalgia. These related conditions often present with similar symptoms, including fatigue, cognitive dysfunction, sleep disturbances, and autonomic or immune system irregularities. Recognising these commonalities is essential for improving diagnosis and care pathways for patients.
Who is affected?
Global prevalence estimates of ME/CFS are estimated to be 0.2% to 1% of the total population, suggesting approximately 48,000 to 250,000 people in Australia may be affected by the condition.6 These figures are likely to increase when accounting for related conditions such as Long COVID, fibromyalgia and POTS, which share overlapping symptoms.6
Disclaimer
The resources and documents below are listed by year of publication (within the last 5 years) and as such do not imply any NHMRC preference or priority. The findings and conclusions in these documents and resources are those of the authors and do not represent the official position of NHMRC, nor are they approved by NHMRC.
Information for clinicians
- Canadian guidelines for post COVID-19 condition (2025)
- National Institute for Health and Care Excellence (UK) – Guidelines for myalgic encephalomyelitis (or encephalopathy)/ chronic fatigue syndrome: diagnosis and management 2021
- Frontiers in Paediatrics – Initiating Care of a Patient With Myalgic Encephalomyelitis/ Chronic Fatigue Syndrome (ME/CFS) (2019).
Information for ME/CFS patients and carers
Contact
For further information contact NHMRC at ME_CFS@nhmrc.gov.au
References
1 Institute of Medicine (IOM), Beyond myalgic encephalomyelitis/chronic fatigue syndrome: redefining an illness, The National Academies Press, 2015, doi:10.17226/19012.
2 BM Carruthers, MI Van de Sande, KL De Meirleir et al, 'Myalgic encephalomyelitis: international consensus criteria', Journal of Internal Medicine, 2011, 270(4):327–338, doi:10.1111/j.1365-2796.2011.02428.x.
3 JA Monro and BK Puri, 'A molecular neurobiological approach to understanding the aetiology of chronic fatigue syndrome (myalgic encephalomyelitis or systemic exertion intolerance disease) with treatment implications', Molecular Neurobiology, 2018, 55:7377–7388, doi:10.1007/s12035-018-0928-9.
4 S Johnston, D Staines, S Marshall-Gradisnik, ‘Epidemiological characteristics of chronic fatigue syndrome/ myalgic encephalomyelitis in Australian patients’, Clinical Epidemiology, 2016, 8:97–107, doi:10.2147/CLEP.S96797.
5 JN Baraniuk, ‘Chronic fatigue syndrome: BMJ Best Practice guideline’ British Medical Journal, 2017, accessed 28 August 2025.
6 EJ Lim, YC Ahn, ES Jang, et al., ‘Systematic review and meta-analysis of the prevalence of chronic fatigue syndrome/myalgic encephalomyelitis (CFS/ME)’, Journal of Translational Medicine, 2020, 18:100, doi:10.1186/s12967-020-02269-0.
