The Hidden Burden: Post-Infectious Fatigue in High-Infectious-Disease Settings

Chapter Roadmap: How to Use This Chapter

For patients: read the post-infectious-burden and clinical-diagnosis-without-testing sections to understand why ME/CFS is under-detected outside high-income countries and why diagnosis is harder without testing.

For caregivers: skim the cultural-idiom and traditional-medicine sections for the cultural variation in symptom expression.

For clinicians: focus on the clinical-diagnosis-without-testing section for the diagnostic-access constraint and the disability-recognition sections; the traditional-medicine sections summarize the evidence.

For researchers: read the neglected-disease-framing and global-surveillance sections, then the sentinel-PEM-surveillance and culturally-adapted-PEM-tool sections for the concrete studies needed.

Achievement: Post-Infectious Fatigue Follows Infectious Disease Burden Geographically

Infectious diseases capable of triggering post-infectious ME/CFS — dengue, chikungunya, Zika, tuberculosis, HIV, EBV — are disproportionately concentrated in low- and middle-income countries (LMICs). Dengue alone is endemic in over 100 countries, predominantly in South and Southeast Asia, Latin America, and Sub-Saharan Africa. The first systematic review of post-dengue fatigue, by Condé et al. (2026), quantified what had been suspected: arboviral infections in LMICs produce chronic fatigue syndromes comparable to post-EBV CFS (Conde2026dengueFatigue?). On Reunion Island, a tropical setting, 38% of chikungunya survivors had chronic fatigue at 30-month follow-up — mirroring post-infectious CFS in high-income-country studies (Duvignaud2018chikungunyaFatigue?). Post-acute sequelae across epidemic history — from influenza 1918 through COVID-19 — demonstrate that pandemics produce long-term disability disproportionately in settings with poor acute care infrastructure (Miller2026epidemicsShadow?).

(Certainty: 0.55 — post-dengue fatigue data are first systematic review; post-chikungunya data are single cohort; post-epidemic historical data are narrative. No study applied ME/CFS diagnostic criteria to post-arboviral cohorts.)

Consequence: Every dengue-endemic country has an unrecognized post-dengue fatigue population. Every chikungunya outbreak zone has post-chikungunya chronic fatigue patients who will never receive an ME/CFS diagnosis. The global ME/CFS research community studies only the fraction of post-infectious fatigue cases that occur in places where ME/CFS is diagnosed — a geographic selection bias of unknown but likely enormous magnitude. Severity applicability: unknown — post-arboviral cohorts not stratified by fatigue severity.

Falsifiable prediction: If sentinel PEM screening in one dengue-endemic country (e.g., Vietnam, n≥500 per site) finds post-dengue ME/CFS prevalence (IOM 2015 criteria) below 0.5%, the geographic co-location thesis is quantitatively wrong — post-arboviral ME/CFS is rare despite post-arboviral fatigue being common, and the hidden-burden thesis does not apply to arboviral regions. Conversely, prevalence ≥3% across ≥3 sites would support the thesis.

Speculation: The LMIC Fatigue Blind Spot

If post-infectious ME/CFS occurs at comparable rates across all triggering infections, then countries with the highest infectious-disease burden should have the highest ME/CFS prevalence — but they report the lowest, because they have the least diagnostic infrastructure to detect it. Iran provides the only empirical test of this hypothesis from a middle-income setting: 17.5% of hospitalized COVID-19 patients met Fukuda CFS criteria at 6-month follow-up, mirroring post-COVID CFS prevalence in high-income countries (Simani2021iranCFS?). This suggests the disease is present; what is absent is the diagnostic system to name and count it.

(Certainty: 0.35 — single country (Iran), single center, hospital-based sample, Fukuda criteria only. No replication from other LMIC settings. This is inference from a single data point, not systematic evidence.)

Consequence: If the Iran data generalize, then Vietnam, India, Brazil, and Nigeria — countries with large COVID-19 and dengue burdens — each contain tens to hundreds of thousands of post-infectious ME/CFS patients who have never been counted. Severity applicability: unknown — hospital-based sample limits inference to moderate-severe COVID survivors.

Falsifiable prediction: If sentinel PEM screening in one of the named countries (India, Nigeria, or Brazil) finds post-infectious ME/CFS prevalence (IOM 2015 criteria) below 1%, the LMIC fatigue blind spot is smaller than claimed and the Iran datapoint may represent an outlier rather than the expected pattern. Prevalence ≥5% at ≥2 sites would confirm the blind-spot thesis.