Home › Topics › ME/CFS

ME/CFS

GMJ News knowledge hub · last reviewed August 2026 · Georgian Medical Journal

SummaryStatisticsGlossaryGMJ newsFAQDocumentsOrganizationsResearch

Myalgic encephalomyelitis/chronic fatigue syndrome (ME/CFS) — a complex, debilitating neuroimmune condition affecting approximately 17-24 million people globally (WHO ICD-11: G93.3), predominantly triggered by viral infection and characterised by post-exertional malaise (PEM) — the pathognomonic worsening of all symptoms after minimal physical or cognitive exertion, lasting hours to weeks — has been thrust into the spotlight of global public health by the Long COVID pandemic, with approximately 10-15% of COVID-19 cases developing Long COVID and a substantial proportion meeting ME/CFS diagnostic criteria, dramatically increasing research funding and scientific recognition of a condition previously dismissed as psychosomatic (WHO). Critically: the 2021 NICE guidelines overturned decades of practice by removing graded exercise therapy (GET) as a recommended treatment — as GET worsens outcomes by triggering PEM — in favour of pacing and energy management within the individual’s energy envelope.

Key messages

Post-exertional malaise — the defining feature
PEM (post-exertional malaise) — worsening of ALL symptoms after minimal physical or cognitive exertion, with a delay of hours to days and lasting days to weeks — is the pathognomonic feature of ME/CFS. Any pacing advice must protect against triggering PEM. Graded exercise therapy (GET) is contraindicated precisely because it triggers PEM (NICE 2021).
17-24M globally — majority undiagnosed
ME/CFS affects 17-24 million people globally (WHO ICD-11: G93.3). Despite its prevalence and severity, up to 75-90% are undiagnosed — partly because there is no biomarker test, and because the condition was historically dismissed as psychosomatic.
NICE 2021 — GET removed, pacing recommended
The landmark 2021 NICE guidelines removed graded exercise therapy (GET) from recommended treatments after strong patient evidence that it worsens the condition. Cognitive behavioural therapy (CBT) is no longer recommended as a curative treatment. Pacing and energy management are the cornerstone management approach.
Long COVID — the paradigm shift
Approximately 10-15% of COVID-19 cases develop Long COVID; a substantial proportion meet ME/CFS criteria. This has dramatically increased research funding, scientific recognition and societal awareness — transforming the scientific agenda and removing the outdated psychosomatic stigma that previously blocked progress.
Triggered by viral infection in most cases
ME/CFS most commonly begins after an acute viral infection (Epstein-Barr virus — infectious mononucleosis; enteroviruses; SARS-CoV-2; other respiratory viruses). The "hit-and-run" hypothesis: the virus triggers an abnormal immune response that persists after the infection clears — driving chronic symptoms.
Orthostatic intolerance — an underrecognised feature
Orthostatic intolerance (symptoms worsening on standing — from reduced cerebral perfusion) is present in the majority of ME/CFS patients. Forms: POTS (postural orthostatic tachycardia syndrome — heart rate rise ≥30bpm on standing); NMH (neurally mediated hypotension); delayed orthostatic hypotension. Increased salt/fluid intake and compression garments provide some relief.

Key statistics

17-24M
people with ME/CFS globally (WHO ICD-11 G93.3)
WHO/IOM
75-90%
estimated undiagnosed — no biomarker test available
WHO/CDC
25%
of ME/CFS patients are severely ill (housebound or bedbound)
NICE/WHO
2021
year NICE removed graded exercise therapy (GET) from ME/CFS guidance
NICE 2021
10-15%
of COVID-19 cases develop Long COVID; many meeting ME/CFS criteria
WHO/Lancet 2023
0
FDA-approved treatments for ME/CFS (management is supportive)
WHO/FDA 2024

ME/CFS symptom domains — prevalence and severity (WHO/IOM 2015)

Source: WHO/IOM. PEM is universal; fatigue and cognitive symptoms affect virtually all patients. Severe ME/CFS (25%) is profoundly disabling.

Glossary of key terms

Post-exertional malaise (PEM)
NICE/IOMThe pathognomonic and diagnostic hallmark of ME/CFS — a disproportionate worsening of all symptoms (fatigue, pain, cognitive dysfunction, sleep, orthostatic intolerance) after minimal physical or cognitive exertion. Key features: delayed onset (symptoms worsen 12-48 hours after activity); prolonged duration (hours to weeks); proportionately severe relative to the triggering exertion; often unpredictable threshold. PEM is why graded exercise therapy (GET) — which assumes deconditioning drives symptoms and that gradual exercise will improve function — causes harm. Instead, pacing (staying within the individual's "energy envelope") is essential.
Diagnostic criteria (IOM 2015)
IOM/NICE 2021Institute of Medicine (IOM/NAM) 2015 criteria (now used by NICE 2021 and most international guidelines): ALL required: substantial reduction in ability (>50% of pre-illness function); PEM; unrefreshing sleep. PLUS ≥1 of: cognitive impairment ("brain fog" — difficulty concentrating, memory problems, processing speed); orthostatic intolerance. Duration: ≥6 months; not explained by another condition. Severity subclassifications: mild (can still work/study part-time with major adjustments); moderate (housebound much of time, unable to work); severe (bed-bound most of time); very severe (fully bed-bound, unable to tolerate light/sound/conversation).
Energy envelope theory/pacing
NICE 2021The energy management approach to ME/CFS: each person has a finite daily energy capacity (the "energy envelope"). Activities that exceed this envelope trigger PEM. Pacing means monitoring activity and symptoms carefully; staying within the envelope; using rest proactively; avoiding the "boom-bust" pattern (doing too much on good days, crashing for days after). Activity trackers and heart rate monitors can help identify exertion thresholds. Supported by strong patient evidence; endorsed by NICE 2021.
Graded exercise therapy (GET) — now contraindicated
NICE 2021GET (gradually increasing physical activity over weeks, based on the assumption that ME/CFS is caused by perpetuating factors including deconditioning and illness beliefs) was recommended for ME/CFS for approximately 20 years. Large patient surveys and clinical evidence showed GET causes harm in ME/CFS by triggering PEM and worsening outcomes. NICE 2021 removed GET from recommended treatments. The deconditioning model of ME/CFS is now considered incorrect; ME/CFS appears to be a neuroimmune condition, not a perpetuated psychosomatic illness.
Long COVID and ME/CFS
WHO/Lancet 2023Post-COVID-19 condition (Long COVID) — persistent symptoms ≥12 weeks after acute COVID-19 — affects approximately 10-15% of COVID cases globally. A substantial proportion develop symptoms matching ME/CFS diagnostic criteria: PEM, cognitive dysfunction, unrefreshing sleep, orthostatic intolerance. The COVID-19 pandemic has: (1) vastly increased ME/CFS research funding; (2) produced a large, well-characterised cohort of post-viral illness; (3) driven biomarker research (microclots, autoantibodies, mitochondrial dysfunction, SARS-CoV-2 viral persistence); (4) removed the psychosomatic stigma.
POTS in ME/CFS
WHO/AutonomicPostural orthostatic tachycardia syndrome (POTS) — heart rate rise ≥30 bpm (≥40 bpm in those <19 years) within 10 minutes of standing or on tilt-table testing, with symptoms of orthostatic intolerance (lightheadedness, palpitations, cognitive slowing) — is present in approximately 50-70% of ME/CFS patients. POTS can explain fatigue, cognitive dysfunction and PEM through impaired cerebral autoregulation on standing. Management: increased salt and fluid intake; compression garments; in severe cases: low-dose beta-blockers, fludrocortisone, midodrine.

Latest GMJ coverage

Magnesium Deficiency Linked to Multiple Chronic Diseases: What the Evidence Shows
02/08/2026
Chronic graft-versus-host disease: diagnosis and management emerge as priority in transplant care
10/07/2026
Digital Health Wearables Could Address Women’s Medical Under-Representation
30/05/2026
How Gut Dysbiosis Triggers Systemic Inflammation: A Mechanistic Overview
06/08/2026
The Master Clock: How Your Brain’s Circadian Rhythm Controls Sleep, Hunger, and Mood
06/08/2026
Sleep Deprivation Damages Multiple Body Systems Simultaneously, Six Studies Show
01/08/2026

Frequently asked questions 12 Q&A — structured for Google featured snippets and AI discovery

Knowledge hub: guidelines, conventions and reports

Organizations working in migration and health

Related health topics

Long COVID / Post-COVIDFibromyalgia (central sensitisation)Chronic painUnrefreshing sleepDisability (severe ME/CFS)Depression/anxiety comorbidity

About this hub. Produced by the GMJ News Editorial Team as a public-good service. Every statistic is linked to its primary source. Documents are preserved in the GMJ Repository with full attribution. Georgian Medical Journal · Contact the editorial team
GMJ BriefsView all →
●Takeaway: Engineered quartz surfaces linked to surge in silicosis cases among US workers4 hours ago●Announcement: Beyond Minimum Requirements: New Evidence Suggests Higher Protein Intake Supports Healthy Aging4 hours ago●Kale Delivers Highest Lutein Concentration Among Common Foods4 hours ago●Takeaway: FDA Advisory Panel Endorses Moderna mRNA Flu Vaccine After Earlier Controversy2 hours ago●Announcement: Sri Lanka deploys military to combat surging dengue epidemic as hospitals reach capacity2 hours ago●Key Finding: How Modern Diets Damage the Gut Barrier and Drive Chronic Disease2 hours ago●Quality Alert: Filler Content in Mushroom Supplements Undermines Clinical Claims26 minutes ago●Announcement: Five Foods Cardiologists Recommend for Men’s Heart Health: Evidence from Clinical Practice26 minutes ago●Three Essential Lessons from HPV Vaccination Success: What Healthcare Leaders Should Know1 hour ago●What Healthcare Leaders Need to Know About 340B Enforcement and Claims Data Compliance2 hours ago