Tag: long covid vs ME/CFS

Exploration of Intersections and Divergences of Long COVID and Chronic Fatigue Syndrome

Abstract:

Background: Fatigue is the most common symptom of Long COVID (LC), defined by persistent or newly emerging symptoms that develop at least three months after an initial SARS-CoV-2 infection, in the absence of other identifiable cause. This study investigates the prevalence of myalgic encephalomyelitis/chronic fatigue syndrome (ME/CFS) as a potential comorbidity of LC.

Methods: The study enrolled 37 adult controls with no documented SARS-CoV-2 infection and 32 individuals with a history of infection, categorized as LC-yes (with LC symptoms) and LC-no (without LC symptoms). ME/CFS diagnosis was based on the International Consensus Criteria (ICC).

Results: Among LC-yes cases, the most frequently reported symptoms included post-exertional malaise (PEM); neurosensory, perceptual, or motor disturbances; cognitive impairment; sleep disturbances; pain; impaired thermoregulation; and flu-like symptoms, all occurring significantly more than in the LC-no or control groups. All individuals in the LC-yes group reported PEM. ME/CFS was diagnosed in three LC-yes cases (18.8%), one LC-no case (6.7%), and four control subjects (10.8%), with no statistically significant differences observed among groups. Experiencing more than six symptoms during acute infection, such as fatigue, loss of taste or smell, headache, fever, cough, myalgia, sore throat, shortness of breath, rhinorrhea, and diarrhea, was associated with a twofold higher risk of developing LC.

Conclusion: A substantial proportion of LC-yes individuals experienced PEM; neurosensory, perceptual, or motor disturbances; cognitive impairment; and sleep disturbances, with rates significantly exceeding those in the LC-no and control groups. Nevertheless, only a minority of LC-yes cases (18.8%) satisfied criteria for the ME/CFS, and the prevalence did not significantly differ from LC-no and controls. These findings suggest that while many symptoms of LC overlap with those of ME/CFS, only a subset of LC cases meet established ME/CFS diagnostic criteria.

Source: Kouyoumdjian JA, Yamamoto LA, Graca CR. Exploration of Intersections and Divergences of Long COVID and Chronic Fatigue Syndrome. Cureus. 2025 Aug 20;17(8):e90607. doi: 10.7759/cureus.90607. PMID: 40978825; PMCID: PMC12448662. https://pmc.ncbi.nlm.nih.gov/articles/PMC12448662/ (Full text)

Metabolic neuroimaging of myalgic encephalomyelitis/chronic fatigue syndrome and Long-COVID

Abstract:

Myalgic Encephalomyelitis/Chronic Fatigue Syndrome (ME/CFS) and Long-COVID are complex, disabling conditions that have emerged as significant public health challenges, affecting millions worldwide. Despite their growing prevalence, effective diagnostics and treatments remain limited, largely due to an incomplete understanding of their underlying pathophysiology. Both conditions share hallmark symptoms of chronic fatigue, cognitive dysfunction, and postexertional malaise, but their biological underpinnings remain to be elucidated. Neuroimaging offers a promising, noninvasive window into the brain’s metabolic landscape and has the potential to uncover objective biomarkers for these conditions.

In this mini review, we highlight recent advancements in metabolic neuroimaging, particularly positron emission tomography and magnetic resonance imaging/magnetic resonance spectroscopy, that reveal alterations in glucose and oxygen metabolism, neurotransmitter balance, and oxidative stress. These insights point toward shared disruptions in brain energy metabolism and neuroinflammatory processes, which may underlie the persistent symptoms in both ME/CFS and Long-COVID.

Importantly, while some findings overlap, inconsistencies in metabolite profiles between ME/CFS and Long-COVID underscore the need for further stratification and longitudinal research. Standardizing definitions, such as identifying Long-COVID patients who meet ME/CFS diagnostic criteria, could help improve study comparability.

By summarizing current imaging evidence, this review underscores the potential of neuroimaging to identify imaging biomarkers to advance the clinical diagnosis of Long-COVID and identify therapeutic targets for treatment development. As we continue to face the growing burden of Long-COVID and ME/CFS, metabolic imaging may serve as a powerful tool to bridge gaps in knowledge and accelerate progress toward effective care.

Source: Zhu Y, Quan P, Yamazaki T, Norweg A, Natelson B, Xu X. Metabolic neuroimaging of myalgic encephalomyelitis/chronic fatigue syndrome and Long-COVID. Immunometabolism (Cobham). 2025 Sep 12;7(4):e00068. doi: 10.1097/IN9.0000000000000068. PMID: 40958852; PMCID: PMC12435251. https://pmc.ncbi.nlm.nih.gov/articles/PMC12435251/ (Full text)

Post-COVID-19 Vaccination (or Long Vax) Syndrome: Putative Manifestation, Pathophysiology, and Therapeutic Options

Abstract:

With the global rollout of COVID-19 vaccines, vaccine safety remains a priority. Emerging concerns have raised the potential risk of a long COVID-like syndrome following vaccination, informally called long Vax and provisionally termed post-COVID-19 vaccination syndrome (PCVS). Our narrative review describes the putative manifestation, pathophysiology, and therapeutic approaches of PCVS based on the available evidence, mostly from case reports/series and observational studies.

Our review noted that PCVS typically manifests within days to weeks post-vaccination, with symptoms lasting months to years. PCVS may present as recognized diagnoses such as postural orthostatic tachycardia syndrome (POTS), small-fibre neuropathy (SFN), myalgic encephalomyelitis/chronic fatigue syndrome (ME/CFS), or as long-term sequelae of myocarditis, vaccine-induced thrombotic thrombocytopaenia (VITT), or immune thrombocytopaenia purpura (ITP). Symptomatically, PCVS overlaps with long COVID, such as fatigue and brain fog, but PCVS may involve more frequent paraesthesia and less dyspnoea.

We also review pathophysiological hypotheses of PCVS, focussing on the vaccine-derived spike protein and related immune responses. Finally, we discuss potential therapies used to treat patients with PCVS or related conditions, primarily documented in case reports/series, which could guide future clinical research. Overall, PCVS remains a poorly understood condition that requires more research to elucidate its prevalence, prognosis, risk factors, and treatments.

Source: Yong SJ, Kenny TA, Halim A, Munipalli B, Alhashem YN, AlSaihati H, Al-Subaie MF, Al Kaabi NA, Al Fares MA, Garout M, Sabour AA, Alshiekheid MA, Almansour ZH, Alotaibi J, Alrasheed HA, Alamri AA, Albayat H, Alamodi AS, Tombuloglu H, Mohapatra RK, Hazazi A, Rabaan AA. Post-COVID-19 Vaccination (or Long Vax) Syndrome: Putative Manifestation, Pathophysiology, and Therapeutic Options. Rev Med Virol. 2025 Sep;35(5):e70070. doi: 10.1002/rmv.70070. PMID: 40944962. https://pubmed.ncbi.nlm.nih.gov/40944962/

Long COVID and chronic fatigue syndrome/myalgic encephalitis share similar pathophysiologic mechanisms of exercise limitation

Abstract:

Post-acute sequelae of SARS-CoV-2 (PASC or “long COVID”) and chronic fatigue syndrome/myalgic encephalitis (CFS/ME) share symptoms such as exertional dyspnea. We used exercise oxygen pathway analysis, comprising six parameters of oxygen transport and utilization, to identify limiting mechanisms in both conditions. Invasive cardiopulmonary exercise testing was performed on 15 PASC patients, 11 CFS/ME patients, and 11 controls.

We evaluated the contributions of alveolar ventilation (V̇a), lung diffusion capacity (DL ), cardiac output (Q̇), skeletal muscle diffusion capacity (DM ), hemoglobin (Hb), and mitochondrial oxidative phosphorylation (Vmax) to peak oxygen consumption (V̇O2peak). To simulate targeted interventions, each variable was sequentially normalized to assess its impact on V̇O2peak. V̇O2peak was significantly reduced in both PASC and CFS/ME compared to controls.

Skeletal muscle O2 diffusion (DM ) was the most impaired parameter in both patient groups (p = 0.01). Correcting DM alone improved V̇O2 by 66% in PASC (p = 0.008) and 34.7% in CFS/ME (p = 0.06), suggesting a dominant role for peripheral O2 extraction in exercise limitation. Impaired skeletal muscle oxygen diffusion (DM ) is a shared mechanism of exercise intolerance in PASC and CFS/ME and may represent a therapeutic target. However, our findings are limited by small sample size.

Source: Jothi S, Insel M, Claessen G, Kubba S, Howden EJ, Ruiz-Carmona S, Levine T, Rischard FP. Long COVID and chronic fatigue syndrome/myalgic encephalitis share similar pathophysiologic mechanisms of exercise limitation. Physiol Rep. 2025 Sep;13(17):e70535. doi: 10.14814/phy2.70535. PMID: 40892700. https://physoc.onlinelibrary.wiley.com/doi/10.14814/phy2.70535 (Full text)

ME/CFS and PASC Patient-Derived Immunoglobulin Complexes Disrupt Mitochondrial Function and Alter Inflammatory Marker Secretion

Abstract:

Autoimmunity is a key clinical feature in both post-infectious Myalgic encephalomyelitis / chronic fatigue syndrome (ME/CFS) and Post-Acute Sequelae of COVID (PASC). Passive transfer of immunoglobulins from patients’ sera into mice induces some clinical features of PASC. IgG-induced transfer of disease phenotypes has long been appreciated, yet the exact mechanism of disease development remains largely elusive.

Here, we demonstrate that IgG isolated from post-infectious ME/CFS patients selectively induces mitochondrial fragmentation in human endothelial cells, thereby altering mitochondrial energetics. This effect is lost upon cleavage of IgG into its Fab and Fc fragments.

The digested Fab fragment from ME/CFS alone was able to alter the mitochondrial energetics, resembling the effect of intact IgG. In contrast, the Fc fragment alone induced a hypometabolic phenotype characterized by a trend towards reduced overall ATP content. IgG from ME/CFS and PASC patients induced distinct but separate cytokine secretion profiles in healthy PBMCs.

Proteomics analysis of IgG-bound immune complexes revealed significant changes within the immune complexes of ME/CFS patients, affecting extracellular matrix organization, while the same from PASC patients pointed towards alterations in hemostasis and blood clot regulation.

We demonstrate that IgGs from ME/CFS patients carry a chronic protective stress response that promotes mitochondrial adaptation via fragmentation, without altering mitochondrial ATP generation capacity in endothelial cells. Together, these results highlight a potential pathogenic role of IgG in post-infectious ME/CFS and point to novel therapeutic strategies targeting antibody-mediated metabolic dysregulation.

Source: Bhupesh Kumar Prusty, Zheng Liu, Claudia Hollmann, Sharada Kalanidhi, Andreas Schlosser, Stephanie Lammer, Georgy Nikolayshvili, E mils Edgars Basens, Liba Sokolovska, Zaiga Nora-Krukle, Robert K Naviaux, Gabriela Riemekasten, Rebekka Rust, Judith Bellmann, Friedemann Paul, Franziska Sotzny, Carmen Scheibenbogen. ME/CFS and PASC Patient-Derived Immunoglobulin Complexes Disrupt Mitochondrial Function and Alter Inflammatory Marker Secretion. medRxiv 2025.08.06.25332978; doi: https://doi.org/10.1101/2025.08.06.25332978 https://www.medrxiv.org/content/10.1101/2025.08.06.25332978v1 (Full text available as PDF file)

Functional and Morphological Differences of Muscle Mitochondria in Chronic Fatigue Syndrome and Post-COVID Syndrome

Abstract:

Patients suffering from chronic fatigue syndrome (CFS) or post-COVID syndrome (PCS) exhibit a reduced physiological performance capability. Impaired mitochondrial function and morphology may play a pivotal role. Thus, we aimed to measure the muscle mitochondrial oxidative phosphorylation (OXPHOS) capacity and assess mitochondrial morphology in CFS and PCS patients in comparison to healthy controls (HCs).

Mitochondrial OXPHOS capacity was measured in permeabilized muscle fibers using high-resolution respirometry. Mitochondrial morphology (subsarcolemmal/intermyofibrillar mitochondrial form/cristae/diameter/circumference/area) and content (number and proportion/cell) were assessed via electron microscopy. Analyses included differences in OXPHOS between HC, CFS, and PCS, whereas comparisons in morphology/content were made for CFS vs. PCS. OXPHOS capacity of complex I, which was reduced in PCS compared to HC.

While the subsarcolemmal area, volume/cell, diameter, and perimeter were higher in PCS vs. CFS, no difference was observed for these variables in intermyofibrillar mitochondria. Both the intermyofibrillar and subsarcolemmal cristae integrity was higher in PCS compared to CFS. Both CFS and PCS exhibit increased fatigue and impaired mitochondrial function, but the progressed pathological morphological changes in CFS suggest structural changes due to prolonged inactivity or unknown molecular causes. Instead, the significantly lower complex I activity in PCS suggests probably direct virus-induced alterations.

Source: Bizjak DA, Ohmayer B, Buhl JL, Schneider EM, Walther P, Calzia E, Jerg A, Matits L, Steinacker JM. Functional and Morphological Differences of Muscle Mitochondria in Chronic Fatigue Syndrome and Post-COVID Syndrome. Int J Mol Sci. 2024 Jan 30;25(3):1675. doi: 10.3390/ijms25031675. PMID: 38338957; PMCID: PMC10855807. https://pmc.ncbi.nlm.nih.gov/articles/PMC10855807/ (Full text)

Metabolic adaptation and fragility in healthy 3-D in vitro skeletal muscle tissues exposed to Chronic Fatigue Syndrome and Long COVID-19 sera

Abstract:

Myalgic Encephalomyelitis/Chronic Fatigue Syndrome (ME/CFS) and Long COVID-19 (LC-19) are complex conditions with no diagnostic markers or consensus on disease progression. Despite extensive research, no in vitro model exists to study skeletal muscle wasting, peripheral fatigue, or potential therapies. We developed 3D in vitro skeletal muscle tissues to map muscle adaptations to patient sera over time.

Short exposures (48 hours) to patient sera led to a significant reduction in muscle contractile strength. Transcriptomic analysis revealed the upregulation of glycolytic enzymes, disturbances in calcium homeostasis, hypertrophy, and mitochondrial hyperfusion. Structural analyses confirmed myotube hypertrophy and elevated mitochondrial oxygen consumption in ME/CFS. While muscles initially adapted by increasing glycolysis, prolonged exposure (96-144 hours) caused muscle fragility and fatigue, with mitochondria fragmenting into a toroidal conformation.

We propose that skeletal muscle tissue in ME/CFS and Long COVID-19 progresses through a hypermetabolic state, leading to severe muscular and mitochondrial deterioration. This is the first study to suggest such transient metabolic adaptation

Source: Mughal S, Andújar-Sánchez F, Sabater-Arcis M, Garrabou G, Fernández-Solà J, Alegre-Martin J, Sanmartin Sentañes R, Castro-Marrero J, Esteve-Codina A, Casals E, Fernández-Costa JM, Ramón-Azcón J. Metabolic adaptation and fragility in healthy 3-D in vitro skeletal muscle tissues exposed to Chronic Fatigue Syndrome and Long COVID-19 sera. Biofabrication. 2025 Jul 31. doi: 10.1088/1758-5090/adf66c. Epub ahead of print. PMID: 40744071. https://iopscience.iop.org/article/10.1088/1758-5090/adf66c (Full text available as PDF file)

Causes of symptoms and symptom persistence in long COVID and myalgic encephalomyelitis/chronic fatigue syndrome

Abstract:

Debilitating symptoms for many years can follow acute COVID-19 (“long COVID”), myalgic encephalomyelitis/chronic fatigue syndrome (ME/CFS), and various post-acute infection syndromes (PAISs). Together, long COVID and ME/CFS affect 60-400 million individuals, globally. Many similar underlying biological abnormalities have been identified in both conditions including autoantibodies against neural targets, endothelial dysfunction, acquired mitochondrial dysfunction, and a pro-inflammatory gut microbiome. Each of these abnormalities may directly cause some of the symptoms.

In addition, the symptoms also may be caused by ancient, evolutionarily conserved symptomatic and metabolic responses to vital threats-sickness behavior and torpor-responses mediated by specific, recently discovered neural circuits. These neural circuits constitute a symptom-generating pathway, activated by neuroinflammation, which may be targeted by therapeutics to quell neuroinflammation.

Many factors cause the symptoms to become chronic, including persistent infectious agents (and/or their nucleic acids and antigens) and the fact that many of the underlying biological abnormalities reinforce each other, creating ongoing physiological vicious cycles.

Source:Komaroff AL, Dantzer R. Causes of symptoms and symptom persistence in long COVID and myalgic encephalomyelitis/chronic fatigue syndrome. Cell Rep Med. 2025 Jul 25:102259. doi: 10.1016/j.xcrm.2025.102259. Epub ahead of print. PMID: 40744021. https://www.cell.com/cell-reports-medicine/fulltext/S2666-3791(25)00332-5 (Full text)

Blood parameters differentiate post COVID-19 condition from Myalgic Encephalomyelitis/Chronic Fatigue Syndrome and Fibromyalgia

Abstract:

Post-COVID-19 condition, such as Myalgic Encephalomyelitis/Chronic Fatigue Syndrome (ME/CFS) and Fibromyalgia (FM), are characterized by fatigue, pain, shortness of breath, sleep disturbances, cognitive dysfunction and other symptoms, heavily impacting on patients daily functioning. Moreover, over half of patients end up fulfilling ME/CFS and/or FM clinical criteria after a few months of SARS-CoV-2 infection.

Expression of the toxic human endogenous retrovirus (HERV)-W ENV protein can be induced by viral infection and HERV-W detection was correlated with acute COVID-19 severity and found significantly expressed in post-COVID-19 condition. This study shows that HERV-W ENV may also be present in prepandemic cases of ME/CFS, FM or co-diagnosed with both clinical criteria, suggesting viral participation in these chronic diseases.

To learn whether associated antiviral mechanisms may also show differing patterns of immunological responses, we measured IgM, IgG, IgA and IgE antibody isotypes against SARS-CoV-2 spike and nucleocapsid antigens, the levels of IL-6, IL-8, IL-10, IFNγ and TNFα cytokines, the level of NfL, a neural damage biomarker, as well as some blood cell markers potentially related with fatigue.

Importantly, some of the measured variables showed a capacity to discriminate post-COVID-19 condition cases from all other participants, with 100 % sensitivity and up to 71.9 % specificity providing a new tool for a differential diagnosis between diseases or syndromes with so many overlapping clinical symptoms. Interestingly, the detected markers showed moderate-to-strong correlations with patient symptoms pointing at novel therapeutic opportunities.

Source: Giménez-Orenga K, Pierquin J, Brunel J, Charvet B, Martín-Martínez E, Lemarinier M, Fried S, Lucas A, Perron H, Oltra E. Blood parameters differentiate post COVID-19 condition from Myalgic Encephalomyelitis/Chronic Fatigue Syndrome and Fibromyalgia. Brain Behav Immun Health. 2025 Jul 4;48:101058. doi: 10.1016/j.bbih.2025.101058. PMID: 40726775; PMCID: PMC12302357. https://pmc.ncbi.nlm.nih.gov/articles/PMC12302357/ (Full text)

Comparing DNA Methylation Landscapes in Peripheral Blood from Myalgic Encephalomyelitis/Chronic Fatigue Syndrome and Long COVID Patients

Abstract:

Post-viral conditions, Myalgic Encephalomyelitis/Chronic Fatigue Syndrome (ME/CFS) and Long COVID (LC), share > 95% of their symptoms, but the connection between disturbances in their underlying molecular biology is unclear. This study investigates DNA methylation patterns in peripheral blood mononuclear cells (PBMC) from patients with ME/CFS, LC, and healthy controls (HC).

Reduced Representation Bisulphite Sequencing (RRBS) was applied to the DNA of age- and sex-matched cohorts: ME/CFS (n = 5), LC (n = 5), and HC (n = 5). The global DNA methylomes of the three cohorts were similar and spread equally across all chromosomes, except the sex chromosomes, but there were distinct minor changes in the exons of the disease cohorts towards more hypermethylation.

A principal component analysis (PCA) analysing significant methylation changes (p < 0.05) separated the ME/CFS, LC, and HC cohorts into three distinct clusters. Analysis with a limit of >10% methylation difference and at p < 0.05 identified 214 Differentially Methylated Fragments (DMF) in ME/CFS, and 429 in LC compared to HC. Of these, 118 DMFs were common to both cohorts. Those in promoters and exons were mainly hypermethylated, with a minority hypomethylated. There were rarer examples with either no change in methylation in ME/CFS but a change in LC, or a methylation change in ME/CFS but in the opposite direction in LC. The differential methylation in a number of fragments was significantly greater in the LC cohort than in the ME/CFS cohort.

Our data reveal a generally shared epigenetic makeup between ME/CFS and LC but with specific, distinct changes. Differences between the two cohorts likely reflect the stage of the disease from onset (LC 1 year vs. ME/CFS 12 years), but specific changes imposed by the SARS-CoV-2 virus in the case of the LC patients cannot be discounted. These findings provide a foundation for further studies with larger cohorts at the same disease stage and for functional analyses to establish clinical relevance.

Source: Peppercorn K, Sharma S, Edgar CD, Stockwell PA, Rodger EJ, Chatterjee A, Tate WP. Comparing DNA Methylation Landscapes in Peripheral Blood from Myalgic Encephalomyelitis/Chronic Fatigue Syndrome and Long COVID Patients. Int J Mol Sci. 2025 Jul 10;26(14):6631. doi: 10.3390/ijms26146631. PMID: 40724879. https://www.mdpi.com/1422-0067/26/14/6631 (Full text)