Category: Overlapping Illnesses

The Role of ME/CFS Phenotype in Outpatient Post-COVID Rehabilitation

Abstract:

Post-COVID-19 syndrome (PCS) shares core clinical features with myalgic encephalomyelitis/chronic fatigue syndrome (ME/CFS), particularly persistent fatigue and post-exertional malaise (PEM). However, the prevalence of ME/CFS among PCS rehabilitation outpatients remains unclear.

Medical records of 216 PCS rehabilitation outpatients (57% female; age 47.7±12.5; January 2021 to April 2022) were retrospectively reviewed. During rehabilitation and at a six-month telephone follow-up, ME/CFS was diagnosed using the Canadian Consensus Criteria (CCC). Demographics, body mass index (BMI), FAS, and 6MWT were compared between phenotype and non-phenotype groups using logistic regression, repeated measures ANOVA, and chi-square tests (α=0.05). Of 216 patients, 15 (93% female; age 40.6±10.7; BMI 25.7±5.6) met ME/CFS criteria, yielding a prevalence of 6.9%.

Compared with non-ME/CFS phenotype, ME/CFS phenotype patients were significantly younger (p=0.01) and predominantly female (p=0.003). Baseline FAS was significantly higher (35.8±6.4 vs. 27.8±8.6, p=0.001) and did not improve (Δ +1.3±4.5 vs. Δ -5.1±6.2, p<0.001). Baseline 6MWT was significantly lower (479±132 m vs. 540±96.1 m, p=0.02) and both groups improved over time, but between-group change was not significant (p=0.49).

Approximately 7% of PCS in outpatient rehabilitation exhibit ME/CFS, characterized by severe, persistent fatigue, female predominance, and attenuated functional gains. While the FAS is a practical screening tool, confirmation via CCC remains essential. Future studies should validate these findings and explore tailored rehabilitation strategies for patients with ME/CFS.

Source: Kaiserseder M, Prüfer F, Untersmayer-Elsenhuber E, Zwick RH. Welche Rolle spielt der ME/CFS-Phänotyp in einer ambulanten Post-COVID-Rehabilitation? [The Role of ME/CFS Phenotype in Outpatient Post-COVID Rehabilitation]. Pneumologie. 2026 Mar 30. German. doi: 10.1055/a-2823-6976. Epub ahead of print. PMID: 41911688. https://pubmed.ncbi.nlm.nih.gov/41911688/ (Full text available in German)

Long COVID disability burden in US adults

Abstract:

Background: Five years since the scientific and patient communities first identified the syndrome now known as Long COVID, affected individuals lack treatments, and the US lacks population-based data on its disability burden and correlation with National Institutes of Health (NIH) funding. Moreover, akin to other debilitating conditions it often co-occurs with, e.g., Myalgic encephalomyelitis/chronic fatigue syndrome (ME/CFS) and dysautonomia, Long COVID disproportionately impacts females whose concerns are often marginalized.

Methods: We quantify Long COVID years lived with disability (YLDs= prevalence x disability weight) in US adults and its actual/YLD-commensurate average annual NIH FY2022-2024 funding versus 68 comparator conditions, by sex predominance. We derive Long COVID prevalence from Census Bureau surveys (9/2022-8/2023) and apply disability weights from the Global Burden of Disease Study.

Results: Long COVID YLDs approximate those of Alzheimer’s and Asthma. Long COVID received 14% of its disability commensurate funding: $106 million vs. $739.8 million. ME/CFS is the most under-funded condition, receiving <1% of its YLD proportionate funding. Among conditions analyzed, 24 are female-predominant (we estimate Long COVID funding two ways), 12 male-predominant, and 33 show no sex predominance. Among the 12 below-median funded/above-median YLD conditions, 7/12 are female-predominant, none are male-predominant. Median funding/per YLD is 5.2 times higher for male- vs. female-predominant conditions (7.0 vs 1.3 million per YLD, p = 0.007). Overall, YLDs explain 6.5% of funding variance in a linear regression model using YLD as the sole predictor (Adjusted R-squared: 0.065).

Conclusions: With chronic conditions like Long COVID rising, disability burden merits greater consideration in funding decisions, as does biological sex.

Source: Bonuck K, Gao Q, Congdon S, Kim RS. Long COVID disability burden in US adults. Commun Med (Lond). 2026 Mar 31;6(1):177. doi: 10.1038/s43856-026-01516-7. PMID: 41917225. https://www.nature.com/articles/s43856-026-01516-7 (Full text)

Assessment and Incidence Determination of Myalgic Encephalomyelitis/Chronic Fatigue Syndrome Following a SARS-CoV-2 Infection in a Prospective Cohort of Hospital Employees

Abstract:

Background and Objectives: Post-COVID-19 syndrome (PCS), characterized by persistent fatigue, can develop after a SARS-CoV-2 infection. Myalgic encephalomyelitis/chronic fatigue syndrome (ME/CFS) is a chronic, post-infectious condition marked by severe fatigue and post-exertional malaise. This study aimed to determine the incidence and characteristics of PCS and ME/CFS in a cohort of hospital employees (HEs) with SARS-CoV-2 infections.

Materials and Methods: All HEs who tested SARS-CoV-2-positive between March 2020 and May 2021 who later reported persistent fatigue were invited for an assessment from July to December 2022. Canadian Consensus Criteria were used for the diagnosis of ME/CFS. Assessments included the Montreal Cognitive Assessment (MoCA), and determination of coagulation factors, Epstein-Barr virus (EBV) antibodies and autoantibodies (AABs) against G-protein-coupled receptors (GPCRs).

Results: Of the 221 HEs, 11.8% (95% confidence interval (CI95%) 7.8-16.8, 26/221) still reported persistent fatigue and 3.2% (CI95% 1.3-6.4, 7/221) were diagnosed with ME/CFS. In total, 19 HEs (median age 51.0 years, 89.4% female, 63.1% possible or confirmed nosocomial infection) participated in our assessment. In 42.1% (8/19) MoCA results were below normal. Laboratory values showed increased GPCR AABs in 66.6% (12/18), possible EBV reactivation in 86.7% (13/15) and coagulation parameters suggesting inflammatory processes in 38.9% (7/18).

Conclusions: Our study was able to determine lower-bound incidences of PCS with fatigue and ME/CFS and demonstrated a diagnostic pathway for HEs following SARS-CoV-2 infections. Possible EBV reactivation, increased GPCR AABs and potential coagulation cascade activation may play a pathogenic role.

Source: Tack M, Gruber R, Betting L, Herbrandt S, Wu S, Schlößer B, Häussermann P, Maegele M, Schlang G, Mattner F. Assessment and Incidence Determination of Myalgic Encephalomyelitis/Chronic Fatigue Syndrome Following a SARS-CoV-2 Infection in a Prospective Cohort of Hospital Employees. Medicina (Kaunas). 2026 Mar 3;62(3):480. doi: 10.3390/medicina62030480. PMID: 41901562. https://www.mdpi.com/1648-9144/62/3/480 (Full study)

Putting the PASC score to the test: Clinical vs. statistical accuracy in long COVID diagnosis

Abstract:

Objective: To validate the RECOVER Post-Acute Sequelae of SARS-CoV-2 infection (PASC) score in a cohort of patients who develop long COVID (LC) or fully recover while iteratively improving the tool’s sensitivity and specificity.

Methods: A cross-sectional study in 130 LC patients followed at LC clinics in Baltimore, MD, USA, who met the National Academies of Sciences, Engineering, and Medicine (NASEM) 2024 LC definition, and 60 SARS-CoV-2 exposed but fully recovered individuals. LC participants were required to have at least one neuropsychiatric symptom. Participants completed comprehensive surveys and questionnaires assessing symptoms based on published methods to determine PASC score. Using the NASEM 2024 LC definition as the “true” condition, we compared evaluation metrics for the RECOVER PASC score cutoff (PASC > 12) and the presence of individual/multiple symptoms. Evaluation metrics (e.g., sensitivity, specificity, F1) were calculated based on these classifications for the overall PASC score and symptom combinations.

Results: The LC cohort (n = 130) had a mean age of 47.2 years and was predominantly female (72%), White (79%), and well-educated (77% > 16 years). Controls (n = 60) were similar demographically. LC diagnosis and PASC scores were significantly associated (χ2 = 102.99, P < 0.001). The PASC score showed excellent specificity (100%) and positive predictive value (PPV; 100%) albeit limited sensitivity (80%), missing 20% of participants with LC. We found that loss of smell/taste, post-exertional malaise, or lack of sexual desire or capacity demonstrated 94% sensitivity, 92% specificity, and 96% PPV, 87% NPV, and an F1 score of 0.949.

Conclusion: Validation of the RECOVER PASC supports its utility and highlights the need for ongoing refinement of the LC definition. We call for national efforts to develop readily implementable clinical tools for LC diagnosis.

Source: Azola A, Dastgheyb RM, Easter R, Parker H, Della Penna C, Santiuste I, Schultz H, Ehrenspeck A, Veenhuis R, Rubin LH. Putting the PASC Score to the Test: Clinical vs. Statistical Accuracy in Long COVID Diagnosis. J Gen Intern Med. 2025 Nov 17. doi: 10.1007/s11606-025-10042-6. Epub ahead of print. PMID: 41249654. https://link.springer.com/article/10.1007/s11606-025-10042-6 (Full text)

Postural Orthostatic Tachycardia Syndrome, Myalgic Encephalomyelitis/Chronic Fatigue Syndrome and Long COVID as Neuroimmune Disorders

Abstract:

Postural orthostatic tachycardia syndrome (POTS), myalgic encephalomyelitis/chronic fatigue syndrome (ME/CFS) and Long COVID are heterogeneous disorders with overlapping complex, multi-factorial and multi-systemic pathophysiology. POTS and ME/CFS are the most common phenotypes of Long COVID that can lead to significant disability and functional impairment.

The exact pathophysiologic mechanisms of these disorders alone or in combination are still being investigated, but important mechanistic factors have been identified, such as autonomic dysfunction, immune dysregulation, autoimmunity, mitochondrial dysfunction, cerebral hypoperfusion, and neuroinflammation.

To this end, we believe that these conditions should be viewed as neuroimmune disorders and should be included in the field of neuroimmunology, with its educational curriculum, training, and clinical care pathways. Including these disorders as part of neuroimmunology subspecialty is the key to advancing the science and clinical care of this underserved patient population with these complex and disabling conditions.

Source: Blitshteyn S, Doherty TA, Steinman L. Postural Orthostatic Tachycardia Syndrome, Myalgic Encephalomyelitis/Chronic Fatigue Syndrome and Long COVID as Neuroimmune Disorders. Immunotargets Ther. 2026 Feb 2;15:581262. doi: 10.2147/ITT.S581262. PMID: 41859298; PMCID: PMC12998959. https://pmc.ncbi.nlm.nih.gov/articles/PMC12998959/ (Full text)

Prevalence of Post-COVID Symptoms Across Variants of Concern and Follow-up Periods: A Systematic Review and Meta-Analysis

Abstract:

Objectives: The interaction between SARS-CoV-2 variants of concern (VoC) and post-COVID symptom duration remains unexplored. This is the first study to evaluate post-COVID prevalence stratified by VoC and follow-up periods.

Methods: Six databases were searched (12/2019-12/2024) for studies of adults with laboratory-confirmed SARS-CoV-2 and symptoms lasting ≥3 months. Data were stratified by VoC (Alpha through Omicron) and follow-up (<6 vs. ≥6 months) to estimate pooled prevalence using random-effects models.

Results: Pooled prevalence across 35 studies (n=159,000) was 28.5% (95% CI: 21.6-36.0), higher in pre-Omicron (35.5%) than Omicron (22.8%) eras (p=0.04). Symptoms persisted beyond six months in 29.9% of cases. Fatigue was the most prevalent symptom across all VoCs and follow-ups followed by brain fog, dyspnea, and sleep impairment. Pre-Omicron variants were linked to dyspnea and anosmia, while Omicron was associated with brain fog and paresthesia. Most symptoms showed no significant reduction beyond six months. Sleep problems were higher in early pre-Omicron cohorts but improved over time; conversely, palpitations and ocular manifestations increased in later pre-Omicron follow-ups.

Conclusions: Post-COVID condition remains a burden despite vaccination. Distinct symptomatology patterns across VoC and timelines highlight the need for tailored management strategies to mitigate long-term global impacts.

Source: Lugtu EJ, Iv DYP, Cabunoc MH, Bautista JL, Pleta FM, Ng JA, Shahid F, Carandang THDC, Lippi G, Henry BM, Fernández-de-Las-Peñas C, Notarte KI. Prevalence of Post-COVID Symptoms Across Variants of Concern and Follow-up Periods: A Systematic Review and Meta-Analysis. Int J Infect Dis. 2026 Mar 10:108522. doi: 10.1016/j.ijid.2026.108522. Epub ahead of print. PMID: 41819160. https://www.ijidonline.com/article/S1201-9712(26)00157-8/fulltext (Full text)

Dysregulated NK-cell gene expression defines the enduring symptoms of long COVID-19

Abstract:

Introduction: Long-term COVID-19 syndrome (LTCS) or “long COVID” is a debilitating post-viral condition affecting approximately 2%–8% of individuals after SARS-CoV-2 infection. It manifests typically ≥3 months post-infection with symptoms persisting for at least 2 months, including fatigue, pulmonary dysfunction, and cognitive impairment, in the absence of alternative diagnoses. The biological mechanisms underlying LTCS remain poorly defined, yet emerging evidence implicates immune dysregulation.

Methods: We profiled plasma antibodies and cytokines from healthy controls (HC, N = 66), convalescents (CONV, N = 24), and LTCS patients (N = 94), followed by multiparametric 14-color flow cytometry of PBMCs from HC (N = 9), CONV (N = 6), and LTCS (N = 23) participants. To gain mechanistic insight, we performed single-cell transcriptomic profiling (scRNA-seq) on PBMCs from HC (N = 8), CONV (N = 6), and LTCS (N = 32) individuals.

Results: LTCS patients exhibited elevated anti-SARS-CoV-2 IgG (spike S1/RBD/N) titers compared with HC, but displayed significantly reduced systemic cytokine levels, including IFN-γ, TNF-α, IL-6, and IL-10. Flow cytometry revealed marked depletion of CD56+CD16+ NK cells and CD56+CD3+ NKT cells, accompanied by altered T-cell activation states. scRNA-seq confirmed NK type I cell loss and uncovered broad transcriptional reprogramming with upregulation of PDCD4, CHD1, CXCR4, and SLC7A5 and downregulation of TGFBR3, RIPOR2, and MBNL1. Gene set enrichment analyses indicated activation of circadian and translational programs and suppression of olfactory receptor, neurotransmitter receptor, and GABA-gated ion-channel pathways. Functional assays validated reduced NK-cell inflammatory capacity in LTCS participants.

Discussion: LTCS is characterized by systemic cytokine attenuation and a quantitative and functional NK-cell deficit coupled to neurosensory pathway suppression. These findings identify NK cells as key sentinels of LTCS pathophysiology and highlight an NK-centric neuroimmune axis as a promising target for biomarker discovery and therapeutic intervention.

Source: Ray U, Schulze Selting A, Perera RP, Yang Z, Lysenkov V, Göpel S, Bitzer M, Salker MS, Ossowski S, Riess O, Casadei N and Singh Y (2026) Dysregulated NK-cell gene expression defines the enduring symptoms of long COVID-19. Front. Immunol. 17:1720551. doi: 10.3389/fimmu.2026.1720551 https://www.frontiersin.org/journals/immunology/articles/10.3389/fimmu.2026.1720551/full?media_id=3855960893360206425_63872469980&media_author_id=63872469980&ranking_info_token=GCBhMjBlODkzODk5NGI0NWIwYjM3MmUwYjkyNDUyYmY5YyWmsvQCJoKX3psNGBMzODU1OTYwODkzMzYwMjA2NDI1KANndG4A&utm_source=ig_text_feed_timeline (Full text)

Clinical relevance of circulating blood microaggregates and reactivation of Epstein Barr Virus in long-term Post-CoVID syndrome patients

Abstract:

Chronic persistence of systemic symptoms after recovery from active CoVID-19 has become a significant disease burden, named post-CoVID syndrome. Among many pathophysiological hypotheses we focus on impaired hemostasis as well as reactivation of latent Epstein-Barr virus.

We now introduce a novel diagnostic morphological approach for visualizing microaggregates circulating in peripheral venous blood, which are large enough to impede capillary blood flow. In addition, secretion of interferon gamma by mononuclear leukocytes in response to peptides of Epstein-Barr virus is increased in these patients.

As a promising therapeutic approach, we provide retrospective data on the effect of anti-thrombotic and virostatic drugs, respectively. In a large number of patients, clinical improvement was observed after platelet inhibition, particularly when EBV was also treated with antiviral therapy.

Source: Wick N, Hermann M, Lisch C, Gerth R, Wick G, Untersmayr E, Marth T, Bachler M, Fries D. Clinical relevance of circulating blood microaggregates and reactivation of Epstein Barr Virus in long-term Post-CoVID syndrome patients. Sci Rep. 2026 Mar 8. doi: 10.1038/s41598-026-42952-8. Epub ahead of print. PMID: 41796205. https://www.nature.com/articles/s41598-026-42952-8 (Full text available as PDF file)

A multiomics recovery factor predicts long COVID in the IMPACC study

Abstract:

BACKGROUND: Following SARS-CoV-2 infection, approximately 10%–35% of patients with COVID-19 experience long COVID (LC), in which debilitating symptoms persist for at least 3 months. Elucidating the biologic underpinnings of LC could identify therapeutic opportunities.

METHODS: We utilized machine learning methods on biologic analytes provided over 12 months after hospital discharge from more than 500 patients with COVID-19 in the IMPACC cohort to identify a multiomics “recovery factor,” trained on patient-reported physical function survey scores. Immune profiling data included PBMC transcriptomics, serum O-link and plasma proteomics, plasma metabolomics, and blood mass cytometry by time of flight (CyTOF) protein levels. Recovery factor scores were tested for association with LC, disease severity, clinical parameters, and immune subset frequencies. Enrichment analyses identified biologic pathways associated with recovery factor scores.

RESULTS: Participants with LC had lower recovery factor scores compared with recovered participants. Recovery factor scores predicted LC as early as hospital admission, irrespective of acute COVID-19 severity. Biologic characterization revealed increased inflammatory mediators, elevated signatures of heme metabolism, and decreased androgenic steroids as predictive and ongoing biomarkers of LC. Lower recovery factor scores were associated with reduced lymphocyte and increased myeloid cell frequencies. The observed signatures are consistent with persistent inflammation driving anemia and stress erythropoiesis as major biologic underpinnings of LC.

CONCLUSION: The multiomics recovery factor identifies patients at risk of LC early after SARS-CoV-2 infection and reveals LC biomarkers and potential treatment targets.

TRIAL REGISTRATION: ClinicalTrials.gov NCT04378777.

FUNDING:

National Institute of Allergy and Infectious Diseases (NIAID), NIH (3U01AI167892-03S2, 3U01AI167892-01S2, 5R01AI135803-03, 5U19AI118608-04, 5U19AI128910-04, 4U19AI090023-11, 4U19AI118610-06, R01AI145835-01A1S1, 5U19AI062629-17, 5U19AI057229-17, 5U19AI057229-18, 5U19AI125357-05, 5U19AI128913-03, 3U19AI077439-13, 5U54AI142766-03, 5R01AI104870-07S1, 3U19AI089992-09, 3U19AI128913-03, and 5T32DA018926-1, 3U19AI1289130, U19AI128913-04S1, R01AI122220); NIH (UM1TR004528); and National Science Foundation (NSF) (DMS2310836).

Source: Gabernet G, Maciuch J, Gygi JP, Moore JF, Hoch A, Syphurs C, Chu T, Doni Jayavelu N, Corry DB, Kheradmand F, Baden LR, Sekaly RP, McComsey GA, Haddad EK, Cairns CB, Rouphael N, Fernandez-Sesma A, Simon V, Metcalf JP, Agudelo Higuita NI, Hough CL, Messer WB, Davis MM, Nadeau KC, Pulendran B, Kraft M, Bime C, Reed EF, Schaenman J, Erle DJ, Calfee CS, Atkinson MA, Brakenridge SC, Melamed E, Shaw AC, Hafler DA, Augustine AD, Becker PM, Ozonoff A, Bosinger SE, Eckalbar W, Maecker HT, Kim-Schulze S, Steen H, Krammer F, Westendorf K; IMPACC Network; Peters B, Fourati S, Altman MC, Levy O, Smolen KK, Montgomery RR, Diray-Arce J, Kleinstein SH, Guan L, Ehrlich LI. A multiomics recovery factor predicts long COVID in the IMPACC study. J Clin Invest. 2025 Sep 9;135(21):e193698. doi: 10.1172/JCI193698. PMID: 40924481; PMCID: PMC12582403. https://pmc.ncbi.nlm.nih.gov/articles/PMC12582403/ (Full text)

Genetic depletion of the early autophagy protein ATG13 impairs mitochondrial energy metabolism, augments oxidative stress, induces the polarization of macrophages to the M1 inflammatory mode, and compromises myelin integrity in skeletal muscle

Abstract:

Objective: M1 macrophage activation is crucial in chronic inflammatory diseases, yet its molecular mechanism is unclear.

Results: Our study showed that hemizygous deletion of the early autophagy gene atg13 (Tg+/-ATG13) disrupts cellular autophagy, hinders mitochondrial oxidative metabolism, and increases reactive oxygen species (ROS) levels in splenic macrophages, leading to M1 polarization. After reducing the expression of the autophagy markers WDFY3 and LC3, flow cytometric analysis of M1/M2 markers (CD40, CD86, CD115, CD163, and CD206), decreasing oxygen metabolism, as evaluated by the ROS-sensor dye DCFDA, and Seahorse oxygen consumption studies revealed that ablation of the atg13 gene impairs mitochondrial function, triggering M1 polarization.

Additionally, redox imbalance may impair Sirtuin-1 activity via nitrosylation, increasing the level of acetylated p65 in macrophages and contributing to the inflammatory response in M1Mφs. Additionally, ablation of the atg13 gene resulted in increased infiltration of M1Mφs into the muscle vasculature, deterioration of myelin integrity in nerve bundles, and a reduction in muscle strength following treadmill exercise.

Conclusions: Our study shows that impaired ATG13-driven autophagy increases inflammation through sirtuin-1 inactivation and NF-κB activation, suggesting a role for ATG13 in post-exertional malaise (PEM).

Source: Toriola MA, Timlin E, Bulbule S, Reyes A, Adedeji OM, Gottschalk CG, Barua A, Arnold LA, Roy A. Genetic depletion of the early autophagy protein ATG13 impairs mitochondrial energy metabolism, augments oxidative stress, induces the polarization of macrophages to the M1 inflammatory mode, and compromises myelin integrity in skeletal muscle. Inflamm Res. 2026 Jan 27;75(1):26. doi: 10.1007/s00011-025-02158-6. PMID: 41591477; PMCID: PMC12847126. https://pmc.ncbi.nlm.nih.gov/articles/PMC12847126/ (Full text)