Tag: long Covid

Haptoglobin Phenotypes Stratify Post-Exertional Cognitive Dysfunction Associated with Altered Cerebral Oxygenation and Metabolic Signatures in Long COVID

Abstract:

Long COVID (LC) is a heterogeneous post-infectious syndrome characterized by persistent symptoms, yet the biological basis underlying its interindividual variability remains poorly understood. Given the clinical overlap between LC and myalgic encephalomyelitis (ME), and prior demonstration that haptoglobin (Hp) phenotypes modulate symptom severity in ME, we investigated whether Hp phenotypes similarly stratify post-exertional cognitive dysfunction in LC.
In this longitudinal observational study, 44 individuals with LC and 20 short-course COVID controls, who recovered rapidly from SARS-CoV-2 infection without persistent symptoms or sequelae, underwent Hp phenotyping alongside metabolomic and physiological profiling before and after a standardized 90 min passive post-exertional challenge. Hp phenotypes identified clinically distinct LC subgroups.
Compared with Hp1-1 individuals, Hp2 allele carriers exhibited greater fatigue, poorer physical function, and more severe post-exertional symptoms. Immediately following the challenge, Hp2-2 participants with LC showed significant cognitive decline, whereas Hp1-1 individuals demonstrated cognitive resilience and more favorable longitudinal cognitive trajectories.
This differential susceptibility was accompanied by higher post-exertional cerebral fractional tissue oxygen extraction in the right hemisphere in Hp1-1 individuals and by distinct metabolic signatures, with Hp2 allele carriers exhibiting lower post-exertional plasma concentrations of citric acid, isethionate, and glucosamine. Lower metabolite levels were associated with poorer cognitive performance.
These findings support Hp phenotypes as promising candidate biomarkers for biological stratification in Long COVID, pending validation in larger independent cohorts.

Source: Moezzi A, Elremaly W, Leveau C, Franco A, Nepotchatykh O, Armstrong CW, Moreau A. Haptoglobin Phenotypes Stratify Post-Exertional Cognitive Dysfunction Associated with Altered Cerebral Oxygenation and Metabolic Signatures in Long COVID. International Journal of Molecular Sciences. 2026; 27(15):7000. https://doi.org/10.3390/ijms27157000 https://www.mdpi.com/1422-0067/27/15/7000 (Full text)

Peripheral blood cytokines during early and post-acute stages of SARS-CoV-2 infection are associated with disease severity and long-term symptoms

Abstract:

Background: U.S. Veterans experience a high burden of COVID-19; characterizing immune responses associated with COVID-19 outcomes could help improve treatment. Changes in peripheral blood cytokines over time may predict both acute outcomes and long COVID symptoms.

Methods: Cytokine concentrations were quantified from peripheral blood collected 0-7 days (early) and 14-42 days (post-acute) after enrollment from SARS-CoV-2 positive participants in the EPIC3 study, a prospective, longitudinal cohort following U.S. Veterans. Responses were correlated with Veterans Affairs Severity Index for COVID-19 criteria and chronic symptoms with the modified Medical Research Council Dyspnea scale, Patient-Reported Outcomes Measurement Information System (PROMIS) Cognitive function, and PROMIS Fatigue scores 3 months after enrollment (60-135 days). Trends in cytokine concentration with COVID-19 severity were assessed. Odds of COVID-19 severity and long-term symptoms were estimated with logistic regression adjusted for sex, age, and morbidity. Longitudinal changes in cytokine concentration were examined for participants sampled during both time periods, by severity and long-term symptom group.

Results: Early HGF, IL-18, IL-1RA, IP-10, and VEGF-A and post-acute MIP-1α and VEGF-A concentrations trended positively with increasing COVID-19 severity (q-values < 0.05, Jonckheere-Terpstra trend test). Increases in EGF, MIP-1β, and RANTES concentration and decreases in MIP-1α concentration over time were associated with mild rather than moderate or severe disease. Increases in MIP-1β and RANTES concentration and decreases in Eotaxin concentration over time were associated with the absence of long-term symptoms.

Conclusions: Worse COVID-19 severity by 30 days was associated with higher early and post-acute period cytokine concentrations. Participants with long-term symptoms did not see resolution of cytokine responses over time.

Source: Mendall C, Li X, Pakanati V, Liu C, Wang T, Morelli D, Korpak A, Baraff A, Isaacs SN, Chang KM, Le E, Holodniy M, Sugimoto JD, Smith NL, Lee JS, Ross JM, Shah JA. Peripheral blood cytokines during early and post-acute stages of SARS-CoV-2 infection are associated with disease severity and long-term symptoms. Front Immunol. 2026 Jul 15;17:1870109. doi: 10.3389/fimmu.2026.1870109. PMID: 42528778; PMCID: PMC13415590. https://pmc.ncbi.nlm.nih.gov/articles/PMC13415590/ (Full text)

Altered TRPM3‐Dependent Cytosolic and Mitochondrial Calcium Influx in Natural Killer Cells of Post‐COVID‐19 Condition Patients

Abstract:

According to the World Health Organization (WHO), approximately 6% of COVID-19 cases develop serious long-term sequelae referred to as post-COVID-19 condition (PCC). Immunological disturbances such as persistent activation of immune cells and reduced cytotoxicity by natural killer (NK) cells are reported as key aspects in PCC.

Recently, electrophysiological studies by our group demonstrated impairment of transient receptor potential melastatin 3 (TRPM3) ion channels in NK cells from PCC patients. The significant reduction in TRPM3 channel function and reduced functional activity by NK cells warrants further investigation. Hence, using live cell calcium (Ca2+) imaging ex vivo, we examined the downstream impact of TRPM3 ion channel dysfunction on intracellular and mitochondrial Ca2+ mobilization in NK cells from N = 8 PCC patients, age and sex matched to N = 8 PCC healthy controls (HC).

Our findings provide new evidence of altered passive and TRPM3-mediated Ca2+ influx, significantly impacting cytoplasmic and mitochondrial Ca2+ mobilization in PCC. Passive cytosolic Ca2+ influx amplitude (p < 0.0001) was significantly reduced in PCC; however, passive mitochondrial Ca2+ mobilization (p < 0.0001) was significantly increased. Importantly, cytoplasmic and mitochondrial response rates (slope, p < 0.001) to pregnenolone sulphate stimulation were significantly reduced in PCC.

Consequently, TRPM3-dependent cytosolic (p < 0.001) and mitochondrial (p < 0.0005) Ca2+ mobilization were significantly reduced in PCC compared with HC. Altered ion channel Ca2+ signalling can severely impact both the immune system and bioenergetic processes, potentially leading to broader systemic dysregulations underpinning the pathomechanism of the PCC condition, and warrants further investigations.

Source: Magawa CT, Eaton-Fitch N, Muraki K, Marshall-Gradisnik S. Altered TRPM3-Dependent Cytosolic and Mitochondrial Calcium Influx in Natural Killer Cells of Post-COVID-19 Condition Patients. Eur J Immunol. 2026 Jul;56(7):e70240. doi: 10.1002/eji.70240. PMID: 42484498; PMCID: PMC13390657.  https://pmc.ncbi.nlm.nih.gov/articles/PMC13390657/ (Full text)

School Difficulties and Long COVID in Children and Adolescents

Abstract:

Objective: Pediatric Long COVID (LC) is an infection-associated chronic condition following SARS-CoV-2 infection. While research has begun to elucidate clinical phenotypes, functional impacts are not well described.

Methods: Cross-sectional data from the NIH-funded Researching COVID to Enhance Recovery (RECOVER) pediatric observational cohort were analyzed to assess associations in school-age children (6 to 11 years) and adolescents (12 to 17 years) between LC and caregiver-reported school-related functional outcomes. LC was defined using RECOVER age group-specific symptom-based LC research indices. The primary outcome was worsening of child grades. Secondary outcomes included difficulty paying attention, limited fun with friends, and having an Individualized Education Program (IEP). Using age-stratified analyses, children with and without LC were matched based on age, sex, and dates of infection and enrollment, to estimate risk ratios (RRs) between LC and each outcome.

Results: The cohort included 1976 children (406 school-age, 1570 adolescent). About 18% of school-age children and 29% of adolescents with LC had reported worsened grades, compared to 7% and 11% without LC, respectively [school-age: adjusted RR 2.18 (95% CI: 1.15-4.11); adolescent: adjusted RR 2.39 (95% CI: 1.86-3.06)]. In both age groups, children with LC were more likely to have difficulty paying attention, limited fun with friends, and IEPs.

Conclusions: LC in school-age children and adolescents was negatively associated with functional school-related outcomes, including academic performance, attention, and peer interactions. As LC affects a substantial proportion of U.S. children, these findings highlight the urgent need to develop, provide, and evaluate school-related services for children and adolescents with LC.

Source: Reeder HT, Kleinman LC, Stockwell MS, Thaweethai T, Pant DB, Rhee KE, Jernigan TL, Snowden JN, Salisbury AL, Kinser PA, Milner JD, Tantisira KG, Warburton D, Mohandas S, Wood JC, Fitzgerald ML, Carmilani M, Krishnamoorthy A, Foulkes AS, Gross RS; RECOVER-Pediatrics Consortium. School Difficulties and Long COVID in Children and Adolescents. Acad Pediatr. 2026 Jul;26(5):103314. doi: 10.1016/j.acap.2026.103314. Epub 2026 Apr 3. PMID: 41936816; PMCID: PMC13386493. https://pmc.ncbi.nlm.nih.gov/articles/PMC13386493/ (Full text)

Microstructural alterations in brain tissue of ME/CFS and long COVID using diffusion tensor imaging and diffusion kurtosis imaging

Abstract:

Introduction: Myalgic Encephalomyelitis/Chronic Fatigue Syndrome (ME/CFS) and long COVID have overlapping symptoms, such as profound fatigue, cognitive impairment, post-exertional malaise, pain and sleep disturbances that are debilitating and reduce quality of life. While Magnetic Resonance Imaging (MRI) techniques, specifically Diffusion Tensor Imaging (DTI) and Diffusion Kurtosis Imaging (DKI), have been used to investigate brain tissue microstructure in ME/CFS or long COVID, no study has yet combined these modalities to directly compare tissue microstructural differences between people living with ME/CFS and long COVID.

Methods: We recruited 37 ME/CFS participants (Age: 43.56 ± 12.5), 19 long COVID participants (Age: 47.92 ± 13.3), and 27 healthy controls (Age: 37.9 ± 10.4). Data were acquired using a 3 Tesla (3T) Prisma MRI scanner. DTI and DKI metrics were determined using MRtrix v3.0.7 and Designer V2.0 software, respectively. Voxel-based statistical analysis of cohort differences was performed using the Statistical Parametric Mapping (SPM12) toolbox in MATLAB. Correlation analysis was performed between DTI, DKI metrics and clinical measures such as duration of illness, fatigue severity, SF36 domains and WHODAS domains.

Results: Compared with healthy controls, individuals with ME/CFS showed microstructural alterations in the cingulum, supplementary motor areas, and parts of the corpus callosum (all p < 0.05). Long COVID participants demonstrated microstructural alterations in regions including the fusiform and precentral gyrus and in major white matter tracks (all p < 0.05). Direct comparisons between ME/CFS and long COVID revealed difference in the left corona radiata (p = 0.001).

Conclusion: This study identifies distinct tissue microstructural alterations in ME/CFS and long COVID and offers a vital insight into the neuropathological basis of shared symptoms in both conditions.

Source: Singh TB, Marshall-Gradisnik S, Barnden L, Eaton-Fitch N, Huynh TH, Inderyas M, Thapaliya K. Microstructural alterations in brain tissue of ME/CFS and long COVID using diffusion tensor imaging and diffusion kurtosis imaging. Front Med (Lausanne). 2026 Jul 17;13:1824498. doi: 10.3389/fmed.2026.1824498. PMID: 42539798; PMCID: PMC13424405. https://pmc.ncbi.nlm.nih.gov/articles/PMC13424405/ (Full text)

Central noradrenergic deficiency in post-infectious chronic fatigue: Neurobehavioral correlates

Abstract:

Fatigue, brain fog and post-exertional malaise are major features of post-infectious myalgic encephalomyelitis/chronic fatigue syndrome and post-acute sequelae of severe acute respiratory syndrome coronavirus 2. To date, no specific neurotransmitter abnormalities have been found in either condition. We examined the possibility of central catecholaminergic involvement and clinical correlates in post-infectious myalgic encephalomyelitis/chronic fatigue syndrome and post-acute sequelae of severe acute respiratory syndrome coronavirus 2 groups compared to healthy volunteers and, as positive controls, Parkinson’s disease patients.

In an observational, cross-sectional cohort study conducted at the National Institutes of Health Clinical Center we measured CSF levels of catecholamines and metabolites in the four groups and assessed correlations with neurobehavioral measures. CSF indices of the central Norepinephrine Pathway (norepinephrine + 3,4-dihydroxyphenylglycol + 3-methoxy-4-hydroxyphenylglycol) and Dopamine Pathway (dopamine + 3,4-dihydroxyphenylacetic acid + homovanillic acid) were measured and related to patient-recorded outcomes and physiological assessments.

Mean values for Norepinephrine Pathway activity (in pmol/mL) were lower in the post-infectious myalgic encephalomyelitis/chronic fatigue syndrome, post-acute sequelae of severe acute respiratory syndrome coronavirus 2, and Parkinson’s disease groups compared to the healthy volunteer cohort (post-infectious myalgic encephalomyelitis/chronic fatigue syndrome (-15.9, 95% confidence interval [-26.1, -5.7], P = 0.0006); post-acute sequelae of severe acute respiratory syndrome coronavirus 2 (-9.62, [-17.9, -1.4], P = 0.015); Parkinson’s disease (-19.4, [-27.5, -11.3], P < 0.0001)).

Post-acute sequelae of severe acute respiratory syndrome coronavirus 2 participants with post-exertional malaise had evidence of central noradrenergic deficiency compared to healthy volunteers (-18.3 [-31.3, -5.3], P = 0.0018). The post-infectious myalgic encephalomyelitis/chronic fatigue syndrome and post-acute sequelae of severe acute respiratory syndrome coronavirus 2 groups did not differ from the healthy group in values for the Dopamine Pathway index. Across all participants, Norepinephrine Pathway activity correlated positively with handgrip duration and general health and negatively with fatigue.

We conclude that post-infectious myalgic encephalomyelitis/chronic fatigue syndrome and post-acute sequelae of severe acute respiratory syndrome coronavirus 2 feature a specific central neurotransmitter pattern involving noradrenergic but not dopaminergic deficiency. The noradrenergic abnormality is associated with major symptoms such as post-exertional malaise.

Source: Aregawi L, Walitt B, Sullivan P, Norato G, Benjamin RN, Goldstein DS. Central noradrenergic deficiency in post-infectious chronic fatigue: neurobehavioral correlates. Brain Commun. 2026 May 13;8(3):fcag173. doi: 10.1093/braincomms/fcag173. PMID: 42205163; PMCID: PMC13202209. https://pmc.ncbi.nlm.nih.gov/articles/PMC13202209/ (Full text)

Risks of autoimmune and inflammatory post-acute COVID-19 conditions: a network cohort study in six European countries, the USA and Korea

Abstract:

Objectives: We aimed to assess the risk of incident autoimmune and inflammatory conditions during the post-acute period of COVID-19.

Design: Descriptive network cohort study.

Setting: Electronic health records from the UK and Dutch primary care, Norwegian linked health registry, hospital records of specialist centres in Spain, France and Korea and healthcare claims from Estonia and the USA.

Participants: We followed individuals between September 2020 and the latest available data from day 91 after a SARS-CoV-2 negative test (comparator) or a COVID-19 record (exposed patients, ie assessing patients during the post-acute phase). We further established a reinfection cohort (any further COVID-19 record among the exposed patients). We followed patients until an outcome, end of study period, death, day 365 or an infection (comparator only) or reinfection (exposed patients only).

Main outcome measures: We assessed postural orthostatic tachycardia syndrome (POTS) diagnoses/symptoms, myalgic encephalomyelitis/chronic fatigue syndrome (ME/CFS) diagnoses/symptoms, multi-inflammatory syndrome (MIS) and several autoimmune diseases (rheumatoid arthritis (RA), juvenile idiopathic arthritis (JIA), systemic lupus erythematosus (SLE), inflammatory bowel disease (IBD) and type 1 diabetes mellitus (T1DM)). Meta-analysed crude incidence rate ratios (IRRs) of outcomes after COVID-19 versus negative testing and after reinfection versus a previous COVID-19 record yield the ratios of respective absolute risks of each assessed outcome. We performed subgroup analyses by age, sex and predominant variant periods.

Results: We included 2 521 812 individuals with a first COVID-19 record, 4 233 145 with a first negative test and 135 551 with a reinfection. Age and sex were largely comparable between exposure groups with a shorter follow-up for the reinfection cohorts. After COVID-19 compared with test-negative patients and equally after reinfection compared with previous COVID-19 patients, we did not observe increased rates for all outcomes and all subgroup analyses. Counts of MIS and JIA were too small for meta-analyses.

Conclusions: In our descriptive meta-analyses of crude IRRs among databases from various countries and settings, we did not observe increased rates of incident POTS, ME/CFS, RA, IBD, SLE and T1DM in COVID-19 versus test-negative or reinfection versus COVID-19 during the first 9 months of the post-acute phase of COVID-19 or reinfection (>90 days postinfection until month 12). Since causal interpretation cannot be made from this study, further causal research is warranted.

Source: Burkard TM, López-Güell K, Català M, Burn E, Delmestri A, Khalid S, Jödicke AM, Dedman D, Oyinlola J, Abellan A, Pérez-Crespo L, Mercadé-Besora N, Duarte-Salles T, Prieto-Alhambra D, Arinze J, Mosseveld M, Kolde R, Meléndez J, López-Blasco R, Martínez Á, Valdivieso B, Delseny D, Mercier G, Kim C, Kim JW, Kostka K, Ramírez-Anguita JM, Mayer MA, Trinh NTH, Nordeng H, Paredes R, Uusküla A, Nishimura A, Loste C, Mateu L, Xie J. Risks of autoimmune and inflammatory post-acute COVID-19 conditions: a network cohort study in six European countries, the USA and Korea. BMJ Public Health. 2026 Jul 24;4(3):e001686. doi: 10.1136/bmjph-2024-001686. PMID: 42516718; PMCID: PMC13404851. https://pmc.ncbi.nlm.nih.gov/articles/PMC13404851/ (Full text)

Pacing and energy management with digital tools for conditions with chronic fatigue: What we know so far in ME/CFS and Long COVID

Introduction:

Why pacing matters in conditions with post‑exertional symptom exacerbation

‘Pacing’, or ‘energy management’, is a structured approach to regulating one’s physical, cognitive, and emotional activities to remain within limits imposed by chronic illnesses such as fibromyalgia, cancer, ME/CFS, and Long COVID [1,2]. Pacing ostensibly prevents post‑exertional symptom exacerbation, notably post‑exertional malaise (PEM), the worsening of fatigue, pain, cognitive dysfunction, and other symptoms following even modest activity. Across the literature, pacing is heterogeneously described as strategies that include activity planning, routine‑setting, pre‑emptive rest, breaking tasks into smaller components, monitoring energy fluctuations, and intentionally avoiding activity “push‑crash” cycles that commonly drive clinical deterioration [3]. In addition to heterogenous implementation, evidence of efficacy is also varied [3–9]. In this article, we will focus on ME/CFS and Long COVID as use case examples.

Historically, pacing emerged as an energy management method encouraging individuals to do as much as they can within their limits, rather than pushing through symptoms or following externally prescribed exercise. The central principle is that of the “energy envelope” [1], which asks individuals to identify the threshold at which activity begins to provoke symptoms and then remain inside that envelope as consistently as possible.

While definitions vary across clinicians, researchers, and patient groups, a consistent theme in both our systematic review and the scoping review is that pacing is individualised and requires ongoing adjustment as symptoms fluctuate [3,7]. Importantly, pacing is now the only management strategy recommended by the 2021 NICE guidelines for ME/CFS [10], underscoring its centrality in clinical care despite the concerning lack of evidence for efficacy. As Long COVID research evolved, pacing increasingly became recognised as a pragmatic, do no harm approach for a condition characterised by varied symptomology, unpredictable recovery patterns, and vulnerability to overexertion [8,11].

Source: Sanal-Hayes NEM, Hayes LD, Mclaughlin M, Sculthorpe NF (2026) Pacing and energy management with digital tools for conditions with chronic fatigue: What we know so far in ME/CFS and Long COVID. PLOS Digit Health 5(7): e0001586. https://doi.org/10.1371/journal.pdig.0001586 https://journals.plos.org/digitalhealth/article?id=10.1371/journal.pdig.0001586 (Full text)

Inflammatory and neuroinjury blood biomarkers across COVID-19 severity groups in individuals with persistent neurological symptoms

Abstract:

Persistent neurological symptoms such as cognitive impairment, fatigue, and neuropsychiatric disturbances are increasingly reported in patients with long COVID, with chronic neuroinflammation and neuronal injury proposed as potential contributors. To characterize inflammatory and neuroinjury-related biomarker patterns, we conducted a case-control study including 325 participants recruited at King Chulalongkorn Memorial Hospital between January 2022 and December 2023, comprising 265 individuals with persistent neurological symptoms following COVID-19 infection and 60 asymptomatic COVID-19 participants who did not develop long COVID symptoms.

Blood samples were analysed for inflammatory cytokines (IL-1β, IL-6, IL-8, TNF-α, IFN-α, IL-4) using multiplex immunoassays, and for neuroinflammatory and neurodegenerative biomarkers, including neurofilament light chain (NfL), glial fibrillary acidic protein (GFAP), phosphorylated tau181, and beta-amyloid peptides (Aβ40, Aβ42) using SIMOA and ELISA platforms. Among 265 participants with complete data (critical = 7, severe = 22, moderate = 79, mild = 157), patients with severe and critical COVID-19 exhibited significantly higher concentrations of IL-6, IL-1β, TNF-α, and IL-8, together with elevated NfL, GFAP, and phosphorylated tau181 levels, and reduced Aβ42/40 ratios.

Strong positive correlations between neurodegenerative biomarkers and pro-inflammatory cytokines were observed in critically ill patients, whereas these associations were weak or absent in mild and moderate cases. Older age was also associated with greater disease severity and increased risk of persistent neurological complications.

These findings indicate that individuals with persistent neurological symptoms following COVID-19, particularly those with a history of severe or critical disease, exhibited higher inflammatory and neuroinjury-related biomarker levels, while blood-based biomarkers such as NfL, GFAP, and phosphorylated tau181 may serve as minimally invasive tools for characterizing neurological involvement and identifying patients at risk of long-term neurological sequelae.

Source: Ruchisrisarod C, Kaewpom T, Wanthong P, Luechaipanit W, Bunprakob S, Ampoot W, Yomrat S, Hemachudha P, Supharatpariyakorn T, Thanapornsangsuth P, Tammachote R, Saraya AW. Inflammatory and neuroinjury blood biomarkers across COVID-19 severity groups in individuals with persistent neurological symptoms. Int J Immunopathol Pharmacol. 2026 Jan-Dec;40:3946320261465568. doi: 10.1177/03946320261465568. Epub 2026 Jul 16. PMID: 42460883; PMCID: PMC13376473. https://pmc.ncbi.nlm.nih.gov/articles/PMC13376473/ (Full text)

Biomarkers of post-acute infection syndrome: a systematic literature review

Abstract:

Background: Post-acute infection syndrome (PAIS) remained underrecognized before the COVID-19 pandemic, which further increased exposure by introducing a novel global cause. The global burden of post-acute COVID syndrome (PACS) and myalgic encephalomyelitis/chronic fatigue syndrome (ME/CFS) alone is estimated at several tens of millions affected worldwide. Biomarker discovery is central to improving PAIS diagnosis and may provide therapeutic targets. This review summarizes current knowledge on biomarkers for PAIS, including PACS and ME/CFS.

Methods: A systematic literature search was conducted in PubMed and Web of Science. Inclusion criteria were: (1) studies including PAIS patients; (2) reporting laboratory or omics biomarkers; and (3) investigating biomarkers or pathomechanisms of PAIS. Although Guillain-Barré syndrome (GBS) is not PAIS, we have included it as a separate mechanistic comparator due to its prevalence in search results and its clinical and immunological similarities to PAIS.

Results: A total of 142 studies analyzing PAIS biomarkers were included. GBS was analyzed separately and later compared with the other results. Overall, the reviewed studies employed heterogeneous approaches. While similar types of data were frequently investigated, analytical methods varied and often focused only on a subset of molecules. The results indicate that amino acid, energy, and lipid metabolism, microbiome, mitochondrial stress, and miRNA networks are affected. All pathways are connected via NF-κB.

Discussion: PAIS is a multisystem disorder rooted in persistent immune activation, metabolic reprogramming, and systemic inflammation, driven not by active viral infection, but by dysregulated host responses. The NF-κB pathway serves as a unifying hub, connecting molecular, cellular, and clinical phenotypes. Our framework enables a shift from symptom-based to mechanism-based classification, paving the way for biologically grounded interventions.

Conclusion: This review synthesizes a broad spectrum of biomarkers in PAIS, integrating findings across pathogens and molecular levels rather than restricting to individual conditions or symptom clusters. This study highlights the differences and commonalities among pathogens and diseases that lead to post-acute sequelae, fills a critical knowledge gap, and provides a foundation for future research and clinical practice. Future studies incorporating multi-omics approaches, longitudinal designs, and larger patient cohorts are needed to validate specific biomarkers and advance the understanding of PAIS.

Source: Wendt K, Schieck M, Gille C, Marschollek M, Illig T, Wolff D, Nee S. Biomarkers of post-acute infection syndrome: a systematic literature review. Front Immunol. 2026 Jun 30;17:1741761. doi: 10.3389/fimmu.2026.1741761. PMID: 42454043; PMCID: PMC13365053. https://pmc.ncbi.nlm.nih.gov/articles/PMC13365053/ (Full text)