Journal of the Pediatric Infectious Diseases Society

Multisystem inflammatory syndrome in children (MIS-C) is a rare but serious condition associated with pediatric SARS-CoV-2 infection. While COVID-19 vaccines prevent infection and reduce severity, less conclusive evidence exists regarding their role in preventing MIS-C during breakthrough infections. This systematic review assessed the impact of SARS-CoV-2 vaccination on MIS-C risk during breakthrough infection. Cross-sectional studies, surveillance studies, and cohort studies were included. Of the 944 studies identified, 6 were included. A significant protective effect was seen in patients who received two doses of SARS-CoV-2 vaccination after exclusion of a biased sample (d= 0.71 [95% CI 0.07 to 1.35; p=0.03]). A trend towards a protective effect was seen after one dose of vaccination, but this effect was not statistically significant. Current literature supports a protective effect of two doses of SARS-CoV-2 vaccination against development of MIS-C in breakthrough COVID-19. The evidence supports clinician advocacy for continued vaccination of children against SARS-CoV-2.

Kawasaki disease (KD) is an acute pediatric vasculitis characterized by dysregulated host immune responses and risk of coronary artery injury. Although a two-transcript IFI27-MCEMP1 axis has been clinically validated to distinguish KD from other febrile illnesses, the long noncoding RNA (lncRNA) context of this interferon-myeloid imbalance remains incompletely understood. We evaluated whether peripheral blood mononuclear cell (PBMC)-derived lncRNAs are altered in KD and associated with the interferon and myeloid components of the IFI27-MCEMP1 transcriptomic axis. Children younger than 8 years with suspected KD were prospectively enrolled at the Children's Hospital of Fudan University from 2024 to 2025. The newly enrolled cohort included 55 children with KD and 48 febrile controls. For integrated immune-transcript association analyses, these data were combined with two previously characterized same-site cohorts, yielding 188 children with KD and 175 febrile controls. Expression of IFI27, MCEMP1, CHROMR, MALAT1, and NEAT1 was measured by reverse transcription quantitative PCR and normalized to GAPDH using {Delta}Ct values. In the newly enrolled cohort, the IFI27-MCEMP1 axis reproduced discrimination between KD and febrile controls, with an area under the receiver operating characteristic curve of 0.88; performance was similar in the integrated cohort, with an area under the curve of 0.89. In PBMC lncRNA analyses, CHROMR and MALAT1 {Delta}Ct values were significantly higher in KD than in febrile controls, indicating lower relative expression, whereas NEAT1 did not show a significant KD-specific differential-expression signal. CHROMR showed the strongest association with the IFI27 interferon-associated component, while MALAT1 showed weaker but directionally informative associations with both IFI27 and MCEMP1, including an inverse association with MCEMP1. These findings support an lncRNA-associated interferon-myeloid immune architecture in KD, marked by coordinated attenuation of IFI27, CHROMR, and MALAT1 together with increased MCEMP1. This PBMC RNA pattern provides a biologically interpretable framework for KD immune dysregulation and generates testable hypotheses regarding RNA-regulatory programs in KD vasculitis.

Objective: Lyme disease diagnosis in children is challenging due to atypical presentations and testing limitations. We sought to evaluate the association between Lyme disease and socio-geographic risk factors in children. Materials and methods: We enrolled children undergoing evaluation for acute Lyme disease at one of eight Pedi Lyme Net pediatric emergency departments located in high Lyme disease incidence states over a ten-year period (2015-2024). We defined a case of Lyme disease with an erythema migrans (EM) lesion or a positive two-tier serology result in a child with signs and/or symptoms of acute disease. We linked each childs primary residential county to the following factors: urban-rural residence, socioeconomic status, population-level disease incidence, wildland-urban interface, and "Lyme disease" Google searches. We performed a multi-level logistic regression analysis to evaluate associations between Lyme disease and county factors after adjusting for individual demographics. Results: Among 5,529 children enrolled, 1,396 (25.2%) had Lyme disease: 101 (7.2%) with early-localized disease, 584 (41.8%) with early-disseminated disease, and 711 (50.9%) with late-disseminated disease. Rural residence (aOR 1.9, 95% CI 1.3-2.9), higher socioeconomic advantage (aOR 1.3, 95% CI 1.1-1.4), more "Lyme disease" Google searches (aOR 1.1, 95% CI 1.0-1.2), and higher wildland urban interface (aOR 1.2, 95% CI: 1.0-1.4) were independently associated with Lyme disease. Conclusion: Incorporating socio-geographic factors alongside clinical data may augment diagnostic risk assessment in children with suspected Lyme disease. However, these factors should be incorporated carefully to ensure clinical assessments are not based on a childs geographic location alone.

In this large multi-center cohort of children evaluated for Lyme disease in a Lyme-endemic emergency department, we assessed the diagnostic accuracy of clinician suspicion and subsequent clinical decision-making for children presenting with monoarthritis. Among 1,582 children with monoarthritis evaluated for Lyme disease, 623 (39%) had Lyme arthritis and 32 (2%) had septic arthritis. Overall, 313 (20%) had an invasive joint procedure (arthrocentesis or arthroscopy), 194 (12%) received parenteral antibiotics, and 376 (24%) were hospitalized. Clinician suspicion had moderate discriminative ability for Lyme disease (area under the receiver operating characteristics curve: 0.75, 95% confidence interval: 0.72-0.77). Children with higher clinician suspicion were less likely to receive parenteral antibiotics or to be hospitalized, although invasive procedure rates were similar. Our findings highlight the challenge of clinically distinguishing Lyme from septic arthritis. Better diagnostic tools are needed to improve timely diagnosis and minimize invasive testing among children with monoarthritis in Lyme-endemic regions.

Background: Diarrheal illness in children leads to 3.5 million care visits and 200,000 hospitalizations annually in the US. Viruses are responsible for most pediatric diarrheal cases, yet limited guidance on distinguishing viral from bacterial etiologies complicates clinical decision-making, especially regarding empiric antibiotic use. Methods: We used clinical and qualitative molecular etiologic data from the Implementation of Molecular Diagnostics for Pediatric Acute Gastroenteritis (IMPACT) study to develop prediction models for viral etiology of diarrhea. We used conditional random forests to identify informative clinical and environmental predictors and evaluated model performance using logistic regression and random forests within a 5-fold cross-validation framework. We conducted external validation using the Alberta Provincial Pediatric Enteric Infection Team (APPETITE) dataset. Results: Variables predictive of viral etiology included younger age, non-bloody diarrhea, winter season, and presence of vomiting. External validation showed that an AUC of 0.82 can be achieved with a parsimonious 5-variable model, yielding a sensitivity of 0.92 and specificity of 0.55 Conclusion: Our results suggest that in North American healthcare settings, clinical prediction models can inform decision-making by identifying children with a high probability of viral diarrhea, improving diagnostic clarity, and reducing unnecessary testing and treatment.

Pediatric Autoimmune Neuropsychiatric Disorders Associated with Streptococcal Infections (PANDAS) is characterized by prepubertal abrupt onset of obsessive-compulsive disorder (OCD). The sine qua non is group A streptococcus (GAS) infection, which is hypothesized to elicit an IgG-class anti-GAS antibody response that cross-reacts with antigens in the basal ganglia. However, the association between GAS antibody (GAS-IgG) levels and PANDAS has been inconsistent, and qualitative differences in GAS-IgG profiles have not been carefully evaluated in well-phenotyped cohorts. Moreover, independent studies have yet to converge on anti-neural autoantibodies that are specific to PANDAS. Here, we used phage display immunoprecipitation sequencing (PhIP-Seq) to perform ultra-deep anti-pathogen antibody repertoire profiling of serum from definitive pediatric PANDAS patients (N = 34) collected as part of a prior double-blind, placebo-controlled clinical trial of intravenous immunoglobulin (IVIg). PANDAS cases were compared to pediatric controls without a history of neuropsychiatric illness (N = 31). To assess for objective evidence of neuroglial injury, serum neurofilament light (NfL) and glial fibrillary acidic protein (GFAP) levels were compared to healthy pediatric controls. Within PANDAS, NfL and GFAP levels were compared between pre- and post-treatment sera. To evaluate for central autoantibodies, a subset of baseline cerebrospinal fluid (CSF) samples (N = 25) was profiled by full-length human protein microarray. Though GAS reactivity by PhIP-Seq was well correlated with clinical anti-DNaseB and anti-streptolysin O titers, there were no quantitative or qualitative differences in GAS-IgG profiles between PANDAS and controls. Furthermore, NfL and GFAP levels did not differ between cases and controls. Within PANDAS, changes in NfL or GFAP levels at six weeks did not differ between placebo and IVIg groups. However, CSF autoantibody profiling by protein microarray revealed infrequent but notable candidate autoantibodies. In one patient, we identified autoantibodies against Argonaute family proteins (AGO-IgG), a marker of autoimmune sensory neuropathy. Longitudinal measurement of AGO-IgG in sera revealed that titers were unchanged after placebo, but decreased after IVIg, coinciding with symptomatic improvement, including a decrease in that patients CY-BOCS score. Overall, these results do not support an etiologic role for GAS-IgG in PANDAS. However, some individuals diagnosed with PANDAS may harbor anti-neural autoantibodies.

BackgroundFrequent enteric infections can damage the small intestine causing inflammation and malabsorption, leading to environmental enteric dysfunction. We aimed to characterize the association between intestinal inflammation and enteric pathogens among children in low- and middle-income countries (LMICs) who presented to care with diarrhea. Methodology/Principle FindingsWe conducted a cross-sectional analysis within the Enterics for Global Health - Shigella Surveillance Study at six LMIC sites: Bangladesh, Kenya, Malawi, Pakistan, Peru, and The Gambia. From August 2022 to July 2024, rectal swabs and whole stool samples were collected from 4,903 children with medically attended diarrhea aged 6-35 months (44.4% females, n=2178/4903; mean age: 15.4 months {+/-} 7.4 months) and were analyzed for Shigella and four fecal inflammatory biomarkers: hemoglobin, lipocalin-2, myeloperoxidase, and calprotectin via Enzyme Linked Immunosorbent Assays. Caregivers and clinicians demonstrated moderate accuracy in identifying blood in stool compared to fecal hemoglobin (area under the curve (AUC)=0.70). Among 10 pathogens evaluated, Shigella-attributable diarrhea had the highest concentrations of calprotectin, hemoglobin, and myeloperoxidase. Shigella culture-/PCR+ episodes had intermediate levels of inflammation between culture-/PCR- and culture+ episodes. In multivariable models restricted to Shigella episodes, dysentery was positively associated and vomiting was negatively associated with biomarker concentrations, with the strongest associations observed for hemoglobin (dysentery geometric mean ratio: 14.91 g/g (95% CI: 8.77, 25.36) and vomiting geometric mean ratio: 0.44 g/g (95% CI: 0.24, 0.81)). Age, sex, and both acute and chronic malnutrition were not associated with inflammatory biomarker concentrations. Conclusions/SignificanceHemoglobin appeared to be a more sensitive marker of blood in stool than visual observation. While Shigella was associated with heightened levels of all inflammatory biomarkers, hemoglobin was most strongly associated with Shigella, especially among attributable and culture positive episodes. The distinct clinical characteristics of Shigella were most closely associated with elevated hemoglobin concentrations, suggesting its potential utility as a point-of-care diagnostic. AUTHOR SUMMARYDiarrhea is common among children under five years of age in low- and middle-income countries (LMICs). Repeated diarrheal illnesses can damage the gut, leading to issues with growth and brain development. We examined fecal samples collected from 4,903 children with diarrhea who were enrolled in the Enterics for Global Health - Shigella Surveillance Study. We tested samples for diarrheal pathogens and measured four inflammatory biomarkers. We found that hemoglobin better identified blood in stool than visual observation of blood. Additionally, certain biomarkers (calprotectin, myeloperoxidase, and most notably hemoglobin) were higher when diarrhea was caused by bacteria such as Shigella than when diarrhea was caused by viruses. Also, we discovered that Shigella episodes identified using molecular diagnostics caused a similar illness as those identified by culture. These results support that Shigella diarrhea episodes identified by molecular diagnostics or culture are more inflammatory than other episodes of diarrhea and may require appropriate antibiotic treatment.

Ganciclovir (GCV), and its orally available pro-drug valganciclovir (VGCV), are preferred therapies for treating congenital cytomegalovirus (cCMV), however, their use carries a significant risk of neutropenia for the child. This risk limits dosing and effectiveness of VGCV, particularly in the treatment of infants with cCMV infection, who are at increased risk for sensorineural hearing loss (SNHL). We hypothesized that an improved understanding of the pharmacokinetics (PK) and pharmacodynamics (PD) of VGCV in cCMV-infected infants at risk for SNHL would inform strategies for optimizing safe and effective VGCV dosing. Participants were enrolled in one of two clinical studies interrogating the PK, safety, and efficacy of VGCV treatment in cCMV-infected infants at risk for SNHL. GCV exhibited a short median half-life of 2.02 h and the median (range) area under the 24 h concentration-time curve (AUC24) was 60.8 (26.8, 99.4) g*h/mL. An AUC24 > 70 g*h/mL was associated with an elevated risk of neutropenia (Fisher's Exact p = 0.029). No associations between GCV PK and hearing outcomes were observed. Taken together, these results indicate vast inter-individual variability in GCV PK that is associated with dose-related toxicity, supporting the need for individualized dosing in the cCMV-infected population.

Background Appendicitis is a readily treatable surgical emergency, yet it remains a cause of preventable death among children in resource-limited settings. While recent studies have documented the global burden of pediatric appendicitis, none have systematically examined its geographic clustering or spatial spillover effects. Understanding whether high-mortality countries cluster geographically, and whether neighboring countries influence each other's outcomes, is essential for designing regional surgical capacity strategies. Methods We conducted a spatial analysis of pediatric appendicitis case fatality rates in children aged 0-14 years across 169 countries from 2000 to 2019. Data were obtained from the Global Burden of Disease Study 2023 and World Bank databases. We calculated global Moran's I to assess spatial autocorrelation, used Getis-Ord Gi* to identify local hotspots, and fitted spatial lag and spatial error regression models to quantify spatial spillovers while adjusting for GDP per capita, physician density, and basic sanitation access. Results Global Moran's I was 0.621 in 2000 (p < 0.001), 0.621 in 2010 (p < 0.001), and 0.592 in 2019 (p < 0.001), indicating strong and persistent spatial clustering. Hotspots at 99% confidence were consistently concentrated in sub-Saharan Africa and parts of South Asia, with little change in geographic distribution over two decades. The spatial error model provided the best fit (AIC = 212.6), with a spatial error coefficient ({lambda}) of 0.663 (p < 0.001), suggesting that approximately 66% of residual variation was explained by unobserved regional factors. In the final model, higher GDP per capita ({beta} = -0.497, p < 0.001) and higher physician density ({beta} = -0.568, p < 0.001) were independently associated with lower case fatality, while basic sanitation access showed no significant association (p = 0.284). Conclusions Pediatric appendicitis case fatality exhibits strong and persistent geographic clustering. The substantial spatial spillover effect suggests that regional coordination of surgical capacity building may be more effective than country-by-country investments. Priority should be given to hotspot countries in sub-Saharan Africa and South Asia, with emphasis on surgical workforce expansion rather than broad economic development alone.

Background Post-acute sequelae are well described following COVID-19 but may also occur after other respiratory infections and Aedes-borne infections. Evidence remains fragmented due to heterogeneity in study design, populations, and exposure, outcome, and follow-up definitions. Methods We synthesized and compared post-acute sequelae across influenza, RSV-ARI, dengue fever, chikungunya, Zika, and yellow fever. We searched five databases from inception to 25-08-2025 for articles quantifying risk, incidence, or rates of post-acute sequelae following these diseases. Eligible non-randomized observational studies assessed post-acute neurological, psychiatric, gastrointestinal, cardiovascular, respiratory, renal, musculoskeletal, autoimmune, or endocrine outcomes after confirmed infection. Risk of bias was assessed using ROBINS-E. Random-effects meta-analyses with restricted maximum likelihood estimation were conducted when comparable effect estimates were available (PROSPERO #CRD420251124994). Findings 51 studies were included, predominantly from high-income regions. Most were retrospective cohorts using ICD-coded diagnoses; prospective studies used laboratory-confirmed infections. Data sources, comparator groups, exposure definitions, outcome ascertainment, and follow-up periods varied substantially. Meta-analyses were feasible for RSV, influenza, and dengue fever. All RSV-ARI studies were pediatric and assessed infections during infancy, which were associated with higher pooled odds of physician-diagnosed asthma (OR:2.93 [95%CI: 2.12-4.06]). Influenza studies used COVID-19-positive comparators; pooled estimates showed lower risk for neurological (HR:0.82 [0.76-0.89]) and composite outcomes (RR:0.88 [0.82-0.95]), with other organ systems non-significant. Dengue fever studies spanned all ages and showed increased risks of anxiety (HR:1.34 [1.01-1.78]), dementia (HR:1.61 [1.10-2.35]), autoimmune (RR:1.39 [1.17-1.67]), cardiovascular (HR:1.51 [1.27-1.80]), psychiatric (HR:1.17 [1.07-1.28]), and any sequelae (HR:1.19 [1.13-1.25]) versus those without prior infection. Interpretations Post-acute sequelae contribute to overall disease burden following RSV-ARI and dengue fever. The evidence remains limited by heterogeneity in study design, exposure and outcome definitions, comparator selection, and follow-up duration. Greater standardization in study design and reporting is needed to improve comparability and strengthen causal inference.

Background and Objectives: SARS-CoV-2 (COVID-19) continues to mutate, circulate, and adversely impact health and quality of life. While COVID-19 vaccines remain safe and effective, uptake remains low, especially among children, the youngest of whom were not vaccine-eligible until after Omicron and are underrepresented in published research. This study estimated vaccine effectiveness (VE) among under-5-year-olds. Methods: We used Virginia Department of Health surveillance data from June 2022 through October 2022 to conduct a test negative case-control study. We estimated VE derived from odds ratios (ORs) of reported infections using logistic regression among children aged 6-months to 5-years. Results: Using the earliest positive (cases) or negative (controls) post-vaccine-eligible test results, the VE associated with two doses of a COVID-19 vaccine was 78% (95% CI=45%, 93%; p=0.004) in unadjusted analyses and 70% (95% CI=25%, 91%, p=0.023) when adjusting for age, sex, prior testing behavior, and prior reported infections. The adjusted VE was 74% (95% CI=28%, 94%; p=0.025) among those with no prior positives reported and 45% (95% CI=-302%, 97%; p=0.569) among those with a prior positive reported. Conclusions: These results show that even though the vaccine was not closely matched to the dominant variants circulating during the time period analyzed, it was effective at reducing the risk of reported infections. This study adds to the body of knowledge on pediatric COVID-19 VE in an underrepresented age-group and in a rural region, illustrates the utility of surveillance data for evaluation, and can inform vaccine decisions to improve vaccine uptake for young children.

Kawasaki disease (KD) is a systemic vasculitis in young children, and early diagnosis remains challenging when clinical features are incomplete or overlap with those of other febrile illnesses. Because electrocardiography (ECG) is noninvasive and widely available, we investigated whether ECG-derived features could help distinguish complete KD from pediatric patients with fevers. We conducted a single-center retrospective study of hospitalized febrile children aged 1-8 years who underwent digital 12-lead ECG recording during the initial evaluation. Five amplitude features and six timing features extracted from the ECG were used to develop a logistic regression model to distinguish between complete KD and other febrile illnesses. The model discriminated between the KD and non-KD groups in the validation dataset. The prediction score was not significantly correlated with the age and body temperature. S-wave amplitude, the RR interval, and P-and Q-wave amplitudes were suggested to contribute to discrimination. These findings suggest that ECG-derived features may provide adjunctive information for distinguishing complete KD from other febrile illnesses. Author SummaryKawasaki disease is an inflammatory illness in young children that can lead to coronary artery complications if treatment is delayed. Early diagnosis is often difficult because its initial symptoms overlap with those of many common febrile illnesses. We investigated whether a routine 12-lead electrocardiogram (ECG), which is noninvasive, rapid, and widely available, contains information that can help distinguish complete Kawasaki disease from other febrile conditions. We retrospectively analyzed digital ECGs from hospitalized febrile children and extracted waveform amplitude and timing features. Using these features, we built a logistic regression model and evaluated it in a temporally separate validation cohort. The model distinguished patients with Kawasaki disease from patients with fever. P-, Q-, and S-wave amplitudes and the RR interval were repeatedly selected as important contributors, suggesting that both waveform morphology and heart-rate-related information may be relevant. These findings indicate that ECG-derived features may provide useful adjunctive information during the clinical assessment of complete Kawasaki disease.

We assembled a multimodal clinical dataset describing demographics, placement history, prenatal substance exposure (PSE), birth characteristics, adverse childhood experiences (ACEs), International Classification of Diseases (ICD) diagnoses, and laboratory results for 3,685+ pediatric patients evaluated between 2014 and 2024 at the University of Minnesotas Adoption Medicine Clinic (AMC). Data were curated from electronic medical records through a combined manual and automated extraction protocol using a standardized operating procedure. The resulting dataset integrates structured EMR fields including neuropsychological, laboratory, and diagnostic information with manually pulled fields of ACE scores, PSE history, and placement history. We provide an overview of the population represented and describe the datasets structure, variable definitions, and validation procedures. This resource enables investigations into how early adversity impacts medical and developmental outcomes, and provides one of the largest standardized clinical placement history, PSE, and ACE datasets in an adoption and foster care pediatric population.

Background: Shigella is a leading cause of childhood diarrhea in low- and middle-income countries and is increasingly resistant to first-line antibiotics. We conducted a surveillance study to determine the incidence, genomic characteristics, and AMR profiles of Shigella infections in children under five with moderate to severe diarrhea (MSD) in Lusaka, Zambia. Methods: Between 15 September 2020 and 30 November 2021, a prospective cohort study of 1,400 children under five was enrolled during a community census in a peri-urban setting and passively followed for 9.5 months for MSD. During enrollment, socio-demographic data were collected using electronic questionnaires, while clinical data were collected through the DHIS platform. The main outcome, Shigella in diarrheal stool in under 5 children, was detected using culture and Loop-mediated Isothermal Amplification (LAMP) targeting the ipaH gene. Cox proportional hazards models were used to assess the incidence and risk factors of Shigella (ipaH) infections. Whole-genome sequencing (WGS) was used to characterize the genomic diversity and antimicrobial resistance genes, complemented by phenotypic antibiotic susceptibility testing. Results: There were 230 first episodes of Shigella over a follow-up time of 9,581.7 child-months, yielding an incidence of 24.0 (95% CI 21.1-27.3) cases per 1,000 child-months, with the highest incidence among 2 to 3-year-olds. The key risk factors identified were the water source (p=0.025) and age group (p=0.014). Genotypic characterization revealed 10 S. flexneri, 9 S. sonnei, and 3 S. boydii. The S. sonnei isolates formed two clusters, differing in virulence factors and plasmid profiles, indicating two possible circulating strains. Shigella isolates exhibited phenotypic and genotypic multidrug resistance, including against trimethoprim, aminoglycosides, and beta-lactams. Plasmid-mediated quinolone resistance (qnrS1) was identified in four S. flexneri isolates, with these genes located on the IncFIB(K) plasmid, highlighting the potential for horizontal transmission and spread of quinolone resistance in this region. No phenotypic and genotypic resistance to macrolides, the first-line treatment for Shigella in Zambia, was observed. Interpretation: We report a high burden of Shigella with multidrug resistance, including resistance to fluoroquinolones. These findings highlight the increasing resistance of Shigella to first-line antibiotics and underscore the importance of developing safe and effective vaccines, improving WASH conditions, and ongoing AMR surveillance. Funding: The EDCTP2 program, supported by the European Union, the Faculty for the Future Foundation (FFTF), the Netherlands Organization for Health Research and Development (ZonMw), and Health-Holland AMR-Global, Gloria, and Track-AMR.

Shigella sonnei is a human-adapted enteric pathogen with a very low infectious dose and increasing antimicrobial resistance. In high-income settings, transmission is multimodal including sporadic cases/outbreaks associated with food and travel, as well as sustained transmission among sexual networks of men who have sex with men (MSM). Whole-genome sequencing (WGS) now underpins national shigellosis surveillance in the United Kingdom. Hence, consistent, communicable genotyping is essential for case linkage and trend detection across heterogeneous transmission modes. Here, we evaluate the performance of WGS genotyping approaches for granulating outbreaks of S. sonnei shigellosis, particularly considering differential performance in dense sexual transmission where highly clonal MSM-associated sublineages pose distinct clustering challenges. Specifically, we compare performance of the current practice approach (10 SNP-distance clustering based on SNP address [t10]), allele-based methods (EnteroBase cgMLST/HierCC [HC5]), a pathogen-specific genotyping scheme (sonneityper), and two k-mer based approaches (PopPUNK and KPop), on a bona fide UK surveillance dataset (n = 3,639 isolates from between 2016 and 2022), and stratify analyses by demographics (i.e. presumptive MSM [pMSM] versus non-pMSM). Comparison metrics indicate that t10 clustering method groups data more broadly than HC5, and k-mer-based methods may capture genetic variation independent from SNP or allele-based approaches. Clusters derived from k-mer-based methods offer similar resolution to HC5 and reflect different demographics, but had unconvincing utility for this pathogen. These findings suggest a transmission context-aware surveillance workflow for shigellosis in high income settings: anchor routine communication on a portable allele-based backbone and augment with more granular, complementary methods (e.g., k-mer-based micro-partitioning or phylogenetic analysis) in comparatively low genomic-density regions of population structure (e.g., pMSM transmission lineages) to stabilise clusters and reduce artefactual chaining.

Obesity is a chronic inflammatory disease associated with immune dysregulation. However, alterations in adaptive immune function remain unclear, particularly in the setting of childhood obesity and weight loss. We defined peripheral T cell dysregulation in a cross-sectional cohort of pediatric participants across weight categories and in a longitudinal cohort of adolescents with severe obesity undergoing bariatric surgery. We found increased expression of activation markers (including PD-1 and CD69) in non-naive CD8+ T cells whereas non-naive CD4+ T cells were skewed towards Tfh, Th17, and mixed Th2/Th17 populations. Consistent with a hyperactive state, T cells had enhanced capacity for inflammatory cytokine production (including IFN-{gamma} and TNF-), along with enrichment of gene sets associated with cytokine signaling, cell proliferation, and cell death. Notably, these phenotypic, functional, and transcriptional alterations were not fully resolved after bariatric surgery, despite clinically meaningful weight loss. Together, these findings demonstrate that pediatric obesity leads to dysregulation of adaptive immune function with incomplete normalization after weight loss. SUMMARYThe impact of pediatric obesity on immune cell function is not well understood. This study demonstrates that both CD4+ and CD8+ T cells are dysregulated in children living with obesity and further identifies that this dysregulated state persists following clinically significant weight loss.

Objective: Upper respiratory infections (URI) are the major trigger of asthma exacerbations in children with asthma and are more likely to be reported by Black and Mexican American children compared to White children in the US. We aimed to evaluate the extent to which obesity, nicotine exposure, household size, and socioeconomic status (SES) explained this excess URI risk among all children and among children with asthma. Study Design: Data collected on children aged 6-17 years from the National Health and Nutritional Examination Survey (2007-2012) were analyzed using survey weights and a mediation approach. Household SES was analyzed as a cumulative score reflecting income poverty ratio, education, and rental housing. URI was defined as cough, cold, phlegm, runny nose, or other respiratory illness (excluding hay fever and allergies) in the past 7 days. Results: Obesity and serum cotinine, a marker of nicotine exposure, explained little to none of the excess risk of URI while SES explained 36.4% (95% CI=34.1, 38.6) in Black and 28.5% (95% CI=26.7, 30.5) in Mexican American children. Living in rental housing and income poverty ratio<2, explained half (49.6%, 95% CI=46.9-52.3) and 20% (19.7%, 95% CI=18.9-20.5) of the excess URI risk among Black children, respectively. In Mexican American children, rental housing and low educational attainment each explained approximately 15-17% of the excess URI risk. Results were comparable among children with asthma. Conclusions: Markers of poverty, such as rental housing, contributed substantially to the excess risk of URI among Black and Mexican American children, including among those with asthma.

Background. Women living in leishmaniasis-endemic zones are regularly exposed to the sandfly vector in their environments. While case series and laboratory evidence consistently suggest transplacental transmission of Leishmania parasites with deleterious maternal-fetal effects, this issue has received insufficient attention, particularly in areas where the predominant Leishmania species is mainly associated with cutaneous disease (CL). Methodology/Principal Findings. We conducted an exploratory cross-sectional study in a highly endemic zone of Tabasco, Mexico, enrolling 53 women with singleton term deliveries between April 2018 and April 2020. Placental PCR was positive in 18 (34%) participants. Buccal swabs were positive in 11 (21.2%) of 52 newborns. Immunofluorescence confirmed intracellular amastigotes within macrophages near the vascular endothelium of PCR-positive placentas, with no surrounding inflammatory infiltration. Sequencing revealed homology to Leishmania mexicana or L. amazonensis. Birthweight percentile was modestly lower in the PCR-positive group (predicted mean 53.8% vs. 56.5%, p = 0.76), while small for gestational age showed a non-significant trend toward higher prevalence among PCR-positive cases (prevalence ratio = 2.06, 95% CI: 0.32-13.39, p = 0.45). Conclusions/Significance. Subclinical, dynamic transmission of Leishmania parasites typically associated with cutaneous disease was detected in this endemic zone. The presence of L. mexicana in human placentas was confirmed by immunofluorescence and sequencing, without an associated inflammatory response. These findings highlight the potential of CL-associated Leishmania species to reach the placenta and buccal mucosa of newborns, warranting further epidemiological investigation into the consequences of vertical transmission in regions with endemic CL.

Background Reactivation of human herpesviruses (HHVs), particularly EBV, is associated with more severe acute SARS-CoV-2 infections and the development of Long COVID (LC). Observations of higher anti-EBV antibody levels in individuals with LC support the idea that chronic reactivation of HHVs could contribute to LC pathology. HHV shedding in saliva has also been previously associated with saliva hormone levels. This study aims to examine the relationship between salivary shedding of HHV DNA and LC symptoms, as well as cortisol, testosterone, and estradiol levels. Methods We enrolled 45 participants with LC, and 45 age-sex-matched controls. Surveys and validated health questionnaires were used to collect demographics, medical history, and symptom profiles. Saliva was self-collected at waking, 15, 30, and 45 minutes, and 8 and 16 hours after waking, across two consecutive days. Salivary cortisol, testosterone and estradiol were measured, and extracted nucleic acid was tested for EBV, HSV 1/2, HCMV and HHV-6 A/B using multiplex qPCR, plus SARS-CoV-2 and RNaseP using RT-qPCR. Findings Detection of salivary EBV and HHV-6 DNA was highest early in the morning. There were no significant differences in salivary cortisol, testosterone, or estradiol, or in EBV or HHV-6 shedding between the LC and control groups. However, salivary HHV-6 DNA levels were positively associated with a greater aggregated LC propensity score, as well as anxiety and depression scores. Interpretation The observed correlation between salivary HHV-6 shedding and symptom severity suggests HHV-6 may contribute to post-acute disease, though mechanisms remain unclear. While our study did not identify a relationship between salivary EBV shedding and LC, EBV may still play a role at earlier time points in the disease course, or in compartments not sampled here. These findings highlight the potential importance of HHV-6 in LC pathophysiology and underscore the need for longitudinal, multi-compartment studies of herpesvirus reactivation in LC.

Despite the availability of effective vaccines, pneumococcal disease remains a major global health concern. Pneumococcal vaccines are multivalent vaccines that have progressively increased in valency, a change associated with lower antibody titers to individual polysaccharide antigens. Whether increasing vaccine valency influences B cell responses through antigenic competition remains incompletely understood. Here, we studied pneumococcal polysaccharide-specific B cell responses in peripheral blood and lymph nodes of healthy adults following vaccination with the 13-valent pneumococcal conjugate vaccine. Antigen-specific memory B cells in peripheral blood expanded 2 weeks post-vaccination, whereas germinal center formation was delayed and peaked after 4 weeks. Notably, germinal center B cell responses were dominated by a limited number of specificities, in contrast to the more evenly distributed expansion observed in peripheral blood. Together, these data highlight the importance of extrafollicular responses in adult anti-pneumococcal polysaccharide immunity and provide evidence for antigenic competition during lymph node germinal center formation, which may have important implications in the context of multivalent vaccines.