Epidemiology
ME/CFS is a significant public health burden affecting millions worldwide, with prevalence likely underestimated due to underdiagnosis and inconsistent application of diagnostic criteria.
1 Prevalence and Incidence
Global Estimates. A systematic review and meta-analysis of 45 studies found a pooled prevalence of 0.89% (95% CI: 0.60–1.33) using CDC-1994 (Fukuda) criteria (Lim et al. 2020). Applied globally, this suggests approximately 71 million people are affected. However, prevalence estimates vary sub-stantially based on diagnostic criteria used, ranging from 0.39% to 1.40%.
United States Prevalence. The CDC reported in December 2023 that 1.3% of U.S. adults (approximately 3.3 million Americans) have ME/CFS based on National Health Interview Survey data from 2021–2022 (Vahratian et al. 2023). This represents the first official national prevalence estimate using validated survey methodology.
Incidence Rates. Population-based studies estimate incidence at 13.16 per 100,000 person-years in the United States (Vincent et al. 2012). Norwegian registry data demonstrate a bimodal age distribution of new diagnoses, with peaks at 10–19 years and 30–39 years (Bakken et al. 2014).
Post-COVID Prevalence Surge. The RECOVER-Adult Study (2025) found that 4.5% of SARS-CoV-2 infected individuals developed ME/CFS meeting diagnostic criteria, compared to 0.6% in uninfected controls — an approximate 2.8-fold higher incidence (Jason et al. 2025) (the raw 4.5% vs 0.6% ratio overstates the adjusted incidence ratio because infection status and case ascertainment differ between groups). A large electronic health record cohort likewise found elevated new-onset ME/CFS risk that persisted to four years post-infection, with an adjusted hazard ratio of about 1.5 (1.46 hospitalized, 1.56 non-hospitalized; ICD-coded outcome, which underestimates clinically confirmed ME/CFS and so reads smaller than the surveillance-based incidence ratio above) (Hadidchi et al. 2025). Updated estimates suggest the post-COVID era has increased U.S. ME/CFS cases from 1.5 million to 5–9 million, with annual economic impact rising from $36–51 billion to $149–362 billion (Jason and Dorri 2022).
2 Demographic Patterns
Sex Distribution. ME/CFS demonstrates a female predominance with a 3:1 to 4:1 female-to-male ratio across most studies (Bakken et al. 2014) (Lim et al. 2020). However, 35–40% of diagnosed patients are male, representing a substantial burden. The female predominance suggests potential hormonal or immunological factors, though diagnostic bias (dismissing male presentations) may contribute to apparent sex ratios.
Age Patterns. CDC data show prevalence increases with age, peaking at 2.1% among adults aged 60–69 years before declining in older age groups (Vahratian et al. 2023). However, disease onset follows a bimodal distribution with peaks in adolescence (10–19 years) and early middle age (30–39 years), with mean onset age of approximately 31.6 years (Bakken et al. 2014). Approximately 15% of patients become symptomatic before age 18.
Racial and Ethnic Distribution. CDC data show prevalence of 1.5% in White non-Hispanic individuals, 0.8% in Hispanic individuals, and 0.7% in Asian non-Hispanic individuals (Vahratian et al. 2023). However, these data likely reflect diagnostic disparities rather than true prevalence differences—White respondents have 2.94 greater odds of receiving an ME/CFS diagnosis than non-White respondents after controlling for symptom severity (Dimmock, Mirin, and Jason 2024). Population-based studies suggest equal or higher risk in ethnic minorities when diagnostic access is controlled.
Socioeconomic Factors. Prevalence demonstrates an inverse relationship with income: 2.0% among those below the federal poverty level compared to 1.1% among those at 200% or more of the poverty level (Vahratian et al. 2023). This gradient likely reflects bidirectional causation—lower socioeconomic status may increase disease risk through chronic stress and reduced healthcare access, while ME/CFS causes substantial work disability that reduces income. An associated socioeconomic observation is elevated food insecurity: NZ data show ME/CFS and Long COVID patients face elevated rates of food access difficulties, compounded by disability benefit inadequacy (Dey et al. 2026), and US population data confirm that Long COVID is associated with elevated food insecurity across income and education strata (aOR 1.73; (Lin et al. 2025)), mediated in part by employment loss (Datta, Fazlul, and Khan 2025). See Section Quality of Life and Disability Studies for a full treatment of this association, including its limitations.
3 Geographic Distribution
Meta-analysis data show no significant difference in prevalence between Western countries (1.32%) and Asian countries (1.51%) (Lim et al. 2020). Within the United States, rural areas show higher prevalence (1.9%) compared to large metropolitan areas (1.0–1.1%) (Vahratian et al. 2023), potentially reflecting healthcare access differences, occupational exposures, or delayed diagnosis leading to more severe presentations.
4 Risk Factors
Post-Infectious Onset. The majority of ME/CFS cases follow acute infection. Epstein-Barr virus (infectious mononucleosis) is the most studied trigger, with 9–11% of adults and 7–13% of adolescents developing ME/CFS at 6–12 months post-infection (Hickie et al. 2006). Other documented viral triggers include herpesviruses (HHV-6, CMV), enteroviruses, influenza, and SARS-CoV-2. The RECOVER study found that 51% of long COVID patients meet ME/CFS diagnostic criteria (Jason et al. 2025). The post-COVID onset risk is not confined to the first post-infection year: a large electronic health record cohort (\(n = 147{,}377\); Montefiore) found the risk of new-onset ME/CFS remained elevated up to four years after SARS-CoV-2 infection, with an adjusted hazard ratio of 1.46 in hospitalized and 1.56 in non-hospitalized patients versus controls (Hadidchi et al. 2025). None of the acute-phase biomarkers tested (ferritin, D-dimer, LDH, CRP) predicted who would later develop ME/CFS (Hadidchi et al. 2025).
Genetic Susceptibility. Heritability estimates are approximately 10%, similar to irritable bowel syndrome and migraine (Dibble, McGrath, and Ponting 2020). The DecodeME genome-wide association study (2025), the largest ME/CFS genetic study to date (21,620 cases), identified eight significantly associated loci and three key genes—BTN2A2, OLFM4, and RABGAP1L—all involved in viral and bacterial immune responses (DecodeME Consortium, Ponting, et al. 2025). Notably, no shared genetic variants were found with depression or anxiety, supporting the distinction between ME/CFS and psychiatric conditions.
Other Factors. Additional proposed risk factors include prior immune dysregulation, female sex hormones, and environmental exposures. The combination of genetic susceptibility with an infectious trigger likely explains why only a subset of individuals develop ME/CFS following infection.