Lingering echoes of SARS-CoV-2: mechanistic insights and management of long COVID syndrome

Abstract:

Throughout the world-wide COVID-19 pandemic, there has arisen a significant and a sustained public-health issue, whereby a significant proportion of individuals report persistent symptoms, well beyond the acute period of infection. The non-united array of chronic, multisystemic events, such as fatigue, cognitive deficit, respiratory dysfunction, cardiovascular abnormalities, and neuropsychiatric disorders characterize this sequela, which is referred to as LCS. LCS is much more than the starting viral insult, as it causes long-term complications that impact various organ systems.

The current review questions the pathophysiological mechanisms of LCS, including scrutinizing the importance of the dysregulation of immunity, the persistence of viral reservoirs, endothelial dysfunction, autonomic imbalance, and mitochondrial injury. We highlight the heterogeneity of the syndrome and the associated diagnostic and treatment difficulties. In addition, we stress the urgency of powerful biomarkers that will be used to diagnose LCS as early as possible and monitor it over time. Present treatment strategies, including pharmacologic therapy (immunomodulators, anticoagulants, antiviral medications, etc.) and non-pharmacologic treatment (rehabilitative programs, etc.) are discussed against the backdrop of recent clinical findings.

This review incorporates the recent literature and presents a review of potential treatment options that alleviate symptoms and improve the quality of life of LCS patients. Finally, this integrated synthesis can be used by both clinicians and researchers to gain practical information on the diagnosis, treatment, and future treatment directions of LCS.

Source: Yadav JP, Yadav S, Dubey NK, Yadav IP, Pathak P, Verma A. Lingering echoes of SARS-CoV-2: mechanistic insights and management of long COVID syndrome. Inflammopharmacology. 2025 Nov 30. doi: 10.1007/s10787-025-02062-9. Epub ahead of print. PMID: 41318861. https://pubmed.ncbi.nlm.nih.gov/41318861/

The lingering shadow of epidemics: post-acute sequelae across history

Significance:
Long COVID, a chronic multisystemic health condition, impacts hundreds of millions around the world. Long COVID has brought light to other related post-acute infection syndromes (PAIS) that are triggered by a wide array of pathogens. This opinion article highlights historical accounts of PAIS through the centuries and emphasizes the need for integrated approaches to understanding and treating PAIS.
Highlights:

  • New or persistent symptoms following COVID-19, known as ‘long COVID’, occur in an estimated 4–20% of pediatric and 10–20% of adult patients after acute infection with SARS-CoV-2. Long COVID is associated with dysregulation of both innate and adaptive immunity.
  • While long COVID is a relatively new clinical entity, post-acute infection syndromes (PAIS) have been well documented for over a century.
  • A wide variety of pathogens are associated with PAIS, including divergent classes of viruses, bacteria, and parasites. While each PAIS has a unique trigger and pathology, similarities in symptom profiles and immunological findings suggest these conditions may share features or involve overlapping biological mechanisms.
  • Despite being well described in the literature, PAIS remain understudied relative to their high disease burden. Patients often face stigma and psychologization from medical professionals when disease biomarkers are not readily apparent, exemplified by the historic dismissal of myalgic encephalomyelitis/chronic fatigue syndrome (ME/CFS).
Abstract:
The SARS-CoV-2 pandemic has drawn global attention to post-acute infection syndromes (PAIS), with millions affected by post-acute sequelae of COVID-19 (PASC, or Long COVID). While Long COVID is newly defined, PAIS have been described for over a century following epidemic infections. Multiple pathogens – including influenza, Epstein-Barr virus, and Borrelia burgdorferi, among others – can precipitate persistent, poorly understood symptoms. Chronic illnesses such as myalgic encephalomyelitis/chronic fatigue syndrome (ME/CFS) have long been linked to infectious triggers. This recurring association highlights critical knowledge gaps and underscores the need for systematic investigation. Unlike prior pandemics, the current era offers advanced technologies and analytic tools to address these gaps. Defining the biology of Long COVID may yield broader insights into host–pathogen interactions and mechanisms of chronic illness.
Source: Miller CM, Moen JK, Iwasaki A. The lingering shadow of epidemics: post-acute sequelae across history. Trends Immunol. 2025 Dec 4:S1471-4906(25)00267-4. doi: 10.1016/j.it.2025.10.010. Epub ahead of print. PMID: 41350176. https://www.cell.com/trends/immunology/fulltext/S1471-4906(25)00267-4 (Full text)

Identification of Novel Reproducible Combinatorial Genetic Risk Factors for Myalgic Encephalomyelitis in the DecodeME Patient Cohort and Commonalities with Long COVID

Abstract:

Background: Myalgic encephalomyelitis (also known as ME/CFS or simply ME) has severely impacted the lives of tens of millions of people globally, but the disease currently has no accurate diagnostic tools or effective treatments. Identifying the biological causes of ME has proven challenging due to its wide range of symptoms and affected organs, and the lack of reproducible genetic associations across ME populations. This has prolonged misunderstanding, lack of awareness, and denial of the disease, further harming patients.

Methods: We used the PrecisionLife combinatorial analytics platform to identify disease signatures (i.e., combinations of 1-4 SNP-genotypes) that are significantly enriched in two cohorts of ME participants from DecodeME relative to controls from UK Biobank (UKB). We tested whether the number of these signatures possessed by an individual is significantly associated with increased prevalence of ME in a third disjoint cohort of DecodeME participants. We characterized a number of drug repurposing opportunities for a set of candidate core genes whose disease signatures had the strongest association with ME and which were linked to different mechanisms. We then tested gene overlap between the ME signatures identified and previous studies in long COVID, using two independent approaches to explore these shared genetic commonalities.

Results: We identified 22,411 reproducible disease signatures, comprising combinations of 7,555 unique SNPs, that are consistently associated with increased prevalence of ME in three disjoint patient cohorts. The count of reproducible signatures was significantly associated with increased prevalence of ME (p = 4×10-21), and participants with a top 10% signature count had an odds ratio of disease 1.64 times greater than participants with a bottom 10% signature count, confirming that these genetic signatures increase susceptibility for developing ME. These disease signatures map to 2,311 genes. We identified substantial overlap between the genes found by this combinatorial analysis and previous studies. We found that the 259 candidate core genes most strongly associated with ME are enriched in disease mechanisms including neurological dysregulation, inflammation, cellular stress responses and calcium signaling. We demonstrated that 76 out of 180 genes previously linked to long COVID in UKB and the US All of Us cohorts are also significantly associated with ME in the DecodeME cohort. These findings allowed identification of many existing and novel repurposing opportunities, including candidates linked to several genes with shared etiology for long COVID.

Conclusion: These findings provide further evidence that ME is a complex multisystemic condition where the risk of developing the disease has a very clear genetic and biological basis. They give a substantially deeper level of insight into the genetic risk factors and mechanisms involved in ME. The discovery of so many multiply reproducible genetic associations implies that ME is highly polygenic, which has important consequences for its future study and the delivery of clinical care to patients. The striking overlap in genes and mechanisms between long COVID and ME (76 / 180 long COVID genes tested) suggests the potential for development of novel or repurposed drug therapies that could be used to successfully treat either condition. However, although they share significant genetic commonalities, long COVID and ME appear to be best considered as partially overlapping but different diseases.

Source: Lu J, Sun W, Li S, Qu Y, Liu T, Guo S, Feng C, Yang T. Assessment of symptoms in myalgic encephalomyelitis/chronic fatigue syndrome: a comparative study of existing scales. Front Neurol. 2025 Nov 18;16:1618272. doi: 10.3389/fneur.2025.1618272. PMCID: PMC12668935. https://pmc.ncbi.nlm.nih.gov/articles/PMC12668935/ (Full text available as PDF file)

Assessment of symptoms in myalgic encephalomyelitis/chronic fatigue syndrome: a comparative study of existing scales

Abstract:

Myalgic encephalomyelitis/chronic fatigue syndrome (ME/CFS) is a multifaceted disorder characterized by persistent fatigue, post-exertional malaise (PEM), cognitive dysfunction, sleep disturbance, pain, psychological distress, orthostatic intolerance, and impaired multidimensional health status and functioning. In the absence of reliable biomarkers, standardized symptom assessment is essential for accurate diagnosis and comparability across studies.

This narrative literature review synthesized studies identified through PubMed and Web of Science up to June 2024, covering assessment instruments across major ME/CFS symptom domains. Tools were evaluated for their psychometric validity, clinical applicability, and key limitations.

Overall, existing scales demonstrate acceptable reliability but vary in sensitivity and disease specificity. Harmonized, multidimensional, and digitally or objectively validated measures are needed to improve diagnostic precision, longitudinal monitoring, and clinical translation in ME/CFS.

Source: Lu J, Sun W, Li S, Qu Y, Liu T, Guo S, Feng C, Yang T. Assessment of symptoms in myalgic encephalomyelitis/chronic fatigue syndrome: a comparative study of existing scales. Front Neurol. 2025 Nov 18;16:1618272. doi: 10.3389/fneur.2025.1618272. PMID: 41341517; PMCID: PMC12668935. https://pmc.ncbi.nlm.nih.gov/articles/PMC12668935/ (Full text)

Mucosal Viruses in Myalgic Encephalomyelitis/Chronic Fatigue Syndrome: A Missing Piece of the Puzzle?

Abstract:

Myalgic encephalomyelitis/chronic fatigue syndrome (ME/CFS) is a debilitating chronic condition without a definitive aetiology, no reliable diagnostic test, and no proven effective treatment. Despite most patients reporting a post-viral onset of illness, findings to date are conflicting on whether a single virus or multiple viral triggers are involved. Most studies to date have focused on detecting viruses in blood and circulating immune cells with relatively few investigating the presence of viruses in mucosal sites.

In this review, we propose that this represents a critical gap in understanding the pathophysiology of ME/CFS knowledge, as mucosal tissues are primary entry points for most pathogens and often serve as reservoirs where viruses may persist. Consequently, they represent ideal niches for identifying persistent infections in ME/CFS. Emerging evidence from saliva and other mucosal samples in ME/CFS patients is consistent with this proposal and that latent viruses can persist and periodically reactivate in mucosal tissues from where they can potentially contribute to immune dysregulation, chronic inflammation, and increased symptom severity that defines ME/CFS.

Source: Perera KD, Cameron P, Sarwar T, Carding SR. Mucosal Viruses in Myalgic Encephalomyelitis/Chronic Fatigue Syndrome: A Missing Piece of the Puzzle? Int J Mol Sci. 2025 Nov 19;26(22):11161. doi: 10.3390/ijms262211161. PMID: 41303644; PMCID: PMC12652652. https://pmc.ncbi.nlm.nih.gov/articles/PMC12652652/ (Full text)

Differential Characteristics and Comparison Between Long-COVID Syndrome and Myalgic Encephalomyelitis/Chronic Fatigue Syndrome (ME/CFS)

Abstract:

Long-COVID and Myalgic Encephalomyelitis/Chronic Fatigue Syndrome are disabling diseases characterised by ongoing fatigue, post-exertional malaise, cognitive impairment, and autonomic dysfunction. Myalgic Encephalomyelitis/Chronic Fatigue Syndrome typically follows viral infections, whereas Long-COVID exclusively follows SARS-CoV-2 infection, with overlapping but distinct features. This review uses comprehensive searches of online databases to compare their clinical presentations, pathophysiologies, and treatments.

Both Long-COVID and ME/CFS appear to involve multifactorial mechanisms, including viral persistence, immune dysregulation, endothelial dysfunction, and autoimmunity, though their relative contributions remain uncertain. Symptom management strategies are consistent, however. Cognitive behaviour therapy has been successful, and there are minimal drug treatments. Graded exercise therapy occupies a contested place, recommending individualised pacing and multidisciplinary rehabilitation.

Common and exclusive mechanisms must be identified to formulate valuable therapies. A more significant body of research focusing on immune dysfunction as a pathogenic mechanism for advancing the disease and enabling more effective therapies and diagnostics is needed.

Source: Ivanovska M, Homadi MS, Angelova G, Taskov H, Murdjeva M. Differential Characteristics and Comparison Between Long-COVID Syndrome and Myalgic Encephalomyelitis/Chronic Fatigue Syndrome (ME/CFS). Biomedicines. 2025 Nov 17;13(11):2797. doi: 10.3390/biomedicines13112797. PMID: 41301889; PMCID: PMC12650534. https://pmc.ncbi.nlm.nih.gov/articles/PMC12650534/ (Full text)

The Clinical Relevance of Mast Cell Activation in Myalgic Encephalomyelitis/Chronic Fatigue Syndrome

Abstract:

Background/Objectives: Growing evidence suggests that mast cell activation (MCA) may contribute to Myalgic Encephalomyelitis/Chronic Fatigue Syndrome (ME/CFS), a debilitating disorder characterized by persistent fatigue and post-exertional malaise (PEM). Particularly in relation to orthostatic intolerance (OI), including postural orthostatic tachycardia syndrome (POTS), this study aimed to investigate the prevalence and clinical relevance of MCA in an Austrian ME/CFS patient cohort.

Methods: Two data sets were analyzed. The CCCFS data set, a comprehensive, patient-centered online questionnaire consisting of 687 filled surveys, focuses on patient stratification. Self-reported clinical features, disease progression, and treatment responses were analyzed. Preliminary findings were validated in a second, retrospective study, analyzing data of 383 Austrian ME/CFS patients with regard to MCA involvement and OI.

Results: Among followed-up ME/CFS patients, MCA prevalence increased over the disease course, with up to 25.3% meeting the criteria for clinically relevant MCA. ME/CFS patients with Mast Cell Activation Syndrome (MCAS) and OI reported symptom alleviation significantly more often following mast cell-targeted treatment than those without MCAS (p < 0.0001). With regard to IF-channel inhibitors, ME/CFS patients diagnosed with MCAS responded more frequently than those without MCAS (p = 0.076), while no significant differences were observed in response to beta blockers (p = 0.637). In both cohorts, OI, particularly POTS, was significantly more common in patients with MCA involvement.

Conclusions: MCA appears to be a frequent and clinically relevant comorbidity in ME/CFS and is associated with a higher prevalence of OI, particularly POTS. Stratifying patients based on MCA involvement may support personalized treatment approaches and improve clinical outcomes.

Source: Rohrhofer J, Ebner L, Schweighardt J, Stingl M, Untersmayr E. The Clinical Relevance of Mast Cell Activation in Myalgic Encephalomyelitis/Chronic Fatigue Syndrome. Diagnostics (Basel). 2025 Nov 7;15(22):2828. doi: 10.3390/diagnostics15222828. PMID: 41300853; PMCID: PMC12651186. https://pmc.ncbi.nlm.nih.gov/articles/PMC12651186/ (Full text)

To Ground Research in the Lived Experience of Patients and Caregivers, Give Us a Voice!

Abstract:

My daughter has been diagnosed with a range of chronic conditions, including Hyper-mobile Ehlers-Danlos Syndrome and myalgic encephalomyelitis/chronic fatigue syndrome (ME/CFS). I have approached my role as caregiver in the same way I approach my day job leading social science research: reading the literature, carefully observing her condition, and developing hypotheses about her conditions and how they might be treated. I now have more than 7 years of longitudinal observation-a wealth of data-but no easy way to share with the medical research community the hypotheses these observations have engendered and my ideas about how to productively structure future research to accelerate progress toward treatments for her and others like her. In this essay, I share my thoughts on why patient and caregiver observations and hypotheses are important and how the medical research field might tap into them to make faster progress toward effective treatments for complex medical conditions.

Source: Lubell J. To Ground Research in the Lived Experience of Patients and Caregivers, Give Us a Voice! Ann Fam Med. 2025 Nov 24;23(6):570-572. doi: 10.1370/afm.240494. PMID: 41285594. https://www.annfammed.org/content/23/6/570 (Full text)

Functional olfactory impairment and fatigue in post-COVID-19 syndrome including ME/CFS – a longitudinal prospective observational study

Abstract:

Post-COVID-19 syndrome (PCS) affects a significant proportion of individuals, with olfactory impairment and fatigue as prominent long-term symptoms. A subset of PCS patients with pronounced fatigue meets the diagnostic criteria for myalgic encephalomyelitis/chronic fatigue syndrome (ME/CFS), here referred to as PCS-ME/CFS. This study explores the relationship between PCS, fatigue, and olfactory function, and investigates the potential of olfactory impairment as a diagnostic and prognostic marker.

We assessed olfactory function up to 28 months post-COVID-19 in 45 PCS patients (22 PCS, 23 PCS-ME/CFS) using the extended Sniffin’ Sticks test, which evaluates odor threshold, discrimination, and identification, providing a composite score. Fatigue severity and health-related quality of life were assessed using validated questionnaires, a standardized test measured cognitive function, and handgrip strength indicated physical fatiguability. Both PCS and PCS-ME/CFS patients showed significant improvement in olfactory function, with all patients returning to normosmia after 20 months, regardless of diagnosis.

While odor threshold was the most affected olfactory measure in Sniffin’ Sticks testing, odor identification was the only measure that remained impaired over time. Olfactory impairment correlated with cognitive, physical, and mental performance, with stronger correlations in the PCS group, particularly linking better odor discrimination at baseline to improved daily functioning and health-related quality of life after 20 months.

Our findings suggest that odor identification assessed in standardized testing may remain impaired the longest in patients with persisting symptoms after COVID-19, reflecting persisting central processing difficulties. Correlations between olfactory performance, cognitive function, and physical ability point to shared underlying mechanisms. Early olfactory improvements may be linked to better long-term cognitive outcomes, highlighting a possible prognostic role of olfactory function in these patients.

Source: Meyer-Arndt L, Pierchalla G, Mödl L, Wohlrab F, Legler F, Hoppmann U, Kedor C, Wittke K, Freitag H, Konietschke F, Olze H, Paul F, Scheibenbogen C, Bellmann-Strobl J, Förster-Ruhrmann U. Functional olfactory impairment and fatigue in post-COVID-19 syndrome including ME/CFS – a longitudinal prospective observational study. Brain Behav Immun Health. 2025 Oct 14;50:101124. doi: 10.1016/j.bbih.2025.101124. PMID: 41281896; PMCID: PMC12634829. https://pmc.ncbi.nlm.nih.gov/articles/PMC12634829/ (Full text)

Virus Genome Sequences in the Blood of Myalgic Encephalomyelitis/Chronic Fatigue Syndrome Patients

Abstract:

Myalgic Encephalomyelitis/Chronic Fatigue Syndrome (ME/CFS) is a baffling disease. The disease has a wide spectrum of severity, to date has no established molecular marker, no known causation, and no cure. Many patients report in retrospect that they suffered a virus infection prior to suffering their first symptoms of ME/CFS. Therefore, we report a search for virus genome sequences in the cell-free blood of ME/CFS patients and healthy controls. We used a panel of molecular probes to assess the presence or absence of 185 diverse human viruses in each sample. We identified a total of seventeen viruses, with more in the healthy controls than in the ME/CFS patients.

Source: Hyman RW, Xu W, Roy KR, Suresh S, St Onge RP, Davis RW. Virus Genome Sequences in the Blood of Myalgic Encephalomyelitis/Chronic Fatigue Syndrome Patients. medRxiv [Preprint]. 2025 Nov 7:2025.11.06.25339689. doi: 10.1101/2025.11.06.25339689. PMID: 41282945; PMCID: PMC12637746. https://pmc.ncbi.nlm.nih.gov/articles/PMC12637746/ (Full text available as PDF file)