Trends in emergency department visits for bronchiolitis, 1993-2019.

INTRODUCTION: Bronchiolitis is a leading indication for pediatric emergency department (ED) visits and hospitalizations. Our objective was to provide a comprehensive review of national trends and epidemiology of ED visits for bronchiolitis from 1993 to 2019 in the United States. METHODS: We retrospectively reviewed the National Hospital Ambulatory Medical Care Survey (NHAMCS) reporting of ED visits for bronchiolitis for children age <2 years from 1993 to 2019. Bronchiolitis cases were identified using billing codes assigned at discharge. The primary outcome was bronchiolitis ED visit rates, calculated using NHAMCS-assigned patient visit weights. We then evaluated for temporal variation in patient characteristics, facility location, and hospitalizations among the bronchiolitis ED visits. RESULTS: There were an estimated 8 million ED visits for bronchiolitis for children <2 years between 1993 and 2019. Bronchiolitis ED visits rates ranged from 28 to 36 per 1000 ED visits from 1993 to 2010 and increased significantly to 65 per 1000 ED visits in the 2017-2019 time period (p < 0.001). There was no significant change over time in patient age, sex, race and ethnicity, insurance status, hospital type, or triage level upon ED presentation. Approximately half of bronchiolitis ED visits occurred in the winter months throughout the study period. CONCLUSION: In this analysis of 27 years of national data, we identified a recent rise in ED visit rates for bronchiolitis, which have almost doubled from 2010 to 2019 following a period of relative stability between 1993 and 2010.

Misclassification of Both Influenza Infection and Oseltamivir Exposure Status in Administrative Data.

This cross-sectional study examines documented hospitalization for influenza and administration of neuraminidase inhibitors in US children.

Association between severe bronchiolitis in infancy and age 6-year lung function.

BACKGROUND AND OBJECTIVES: Understanding early life risk factors for decreased lung function could guide prevention efforts and improve lung health throughout the lifespan. Our objective was to investigate the association between history of severe (hospitalized) bronchiolitis in infancy and age 6-year lung function. METHODS: We analyzed data from two prospective cohort studies: infants hospitalized with bronchiolitis and a parallel cohort of healthy infants. Children were followed longitudinally, and spirometry was performed at age 6 years. To examine the relationship between history of severe bronchiolitis and primary outcomes - FEV1% predicted (pp) and FEV1/FVCpp - we used multivariable linear regression models adjusted for insurance status, perterm birth, secondhand smoke exposure, breastfeeding status, traffic-related air pollution and polygenic risk score. Secondary outcomes included FVCpp and bronchodilator responsiveness (BDR). RESULTS: Age 6-year spirometry was available for 425 children with history of severe bronchiolitis in infancy and 48 controls. Unadjusted analysis revealed that while most children had normal range lung function, children with a history of severe bronchiolitis had lower FEV1pp and FEV1/FVCpp. In adjusted analyses, the same findings were observed: FEV1pp was 8% lower (p = 0.004) and FEV1/FVCpp was 4% lower (p = 0.007) in children with history of severe bronchiolitis versus controls. FVC and BDR did not differ between groups. CONCLUSIONS: Children with severe bronchiolitis in infancy have decreased FEV1 and FEV1/FVC at age 6 years, compared to controls. These children may be at increased risk for chronic respiratory illness later in life.

Nasopharyngeal fungal subtypes of infant bronchiolitis and disease severity risk.

BACKGROUND: Bronchiolitis is a leading cause of infant hospitalization. Recent research suggests the heterogeneity within bronchiolitis and the relationship of airway viruses and bacteria with bronchiolitis severity. However, little is known about the pathobiological role of fungi. We aimed to identify bronchiolitis mycotypes by integrating fungus and virus data, and determine their association with bronchiolitis severity and biological characteristics. METHODS: In a multicentre prospective cohort study of 398 infants (age <1 year, male 59%) hospitalized for bronchiolitis, we applied clustering approaches to identify mycotypes by integrating nasopharyngeal fungus (detected in RNA-sequencing data) and virus data (respiratory syncytial virus [RSV], rhinovirus [RV]) at hospitalization. We examined their association with bronchiolitis severity-defined by positive pressure ventilation (PPV) use and biological characteristics by nasopharyngeal metatranscriptome and transcriptome data. RESULTS: In infants hospitalized for bronchiolitis, we identified four mycotypes: A) fungiM.restrictavirusRSV/RV, B) fungiM.restrictavirusRSV, C) fungiM.globosavirusRSV/RV, D) funginot-detectedvirusRSV/RV mycotypes. Compared to mycotype A infants (the largest subtype, n = 211), mycotype C infants (n = 85) had a significantly lower risk of PPV use (7% vs. 1%, adjOR, 0.21; 95% CI, 0.02-0.90; p = 0.033), while the risk of PPV use was not significantly different in mycotype B or D. In the metatranscriptome and transcriptome data, mycotype C had similar bacterial composition and microbial functions yet dysregulated pathways (e.g., Fc γ receptor-mediated phagocytosis pathway and chemokine signaling pathway; FDR <0.05). INTERPRETATION: In this multicentre cohort, fungus-virus clustering identified distinct mycotypes of infant bronchiolitis with differential severity risks and unique biological characteristics. FUNDING: This study was supported by the National Institutes of Health.

Respiratory Virus-Specific Nasopharyngeal Lipidome Signatures and Severity in Infants With Bronchiolitis: A Prospective Multicenter Study.

BACKGROUND: In infant bronchiolitis, recent evidence indicates that respiratory viruses (eg, respiratory syncytial virus [RSV], rhinovirus [RV]) contribute to the heterogeneity of disease severity. Of the potential pathobiological molecules, lipids serve as signaling molecules in airway inflammation. However, little is known about the role of the airway lipidome in between-virus heterogeneity and disease severity. METHODS: In this multicenter prospective study of 800 infants hospitalized for RSV or RV bronchiolitis, we analyzed nasopharyngeal lipidome data. We examined discriminatory lipids between RSV and RV infection and the association of the discriminatory lipids with bronchiolitis severity, defined by positive pressure ventilation (PPV) use. RESULTS: We identified 30 discriminatory nasopharyngeal lipid species and 8 fatty acids between RSV and RV infection. In the multivariable models adjusting for patient-level confounders, 8 lipid species-for example, phosphatidylcholine (18:2/18:2) (adjusted odds ratio [aOR], 0.23 [95% confidence interval {CI}, .11-.44]; false discovery rate [FDR] = 0.0004) and dihydroceramide (16:0) (aOR, 2.17 [95% CI, 1.12-3.96]; FDR = 0.04)-were significantly associated with the risk of PPV use. Additionally, 6 fatty acids-for example, eicosapentaenoic acid (aOR, 0.27 [95% CI, .11-.57]; FDR = 0.01)-were also significantly associated with the risk of PPV use. CONCLUSIONS: In infants hospitalized for bronchiolitis, the nasopharyngeal lipidome plays an important role in the pathophysiology of between-virus heterogeneity and disease severity.

Immunoglobulin E-virus phenotypes of infant bronchiolitis and risk of childhood asthma.

Background: Bronchiolitis is the leading cause of infant hospitalization in U.S. and is associated with increased risk for childhood asthma. Immunoglobulin E (IgE) not only plays major roles in antiviral immune responses and atopic predisposition, but also offers a potential therapeutic target. Objective: We aimed to identify phenotypes of infant bronchiolitis by using total IgE (tIgE) and virus data, to determine their association with asthma development, and examine their biological characteristics. Methods: In a multicenter prospective cohort study of 1,016 infants (age <1 year) hospitalized for bronchiolitis, we applied clustering approaches to identify phenotypes by integrating tIgE and virus (respiratory syncytial virus [RSV], rhinovirus [RV]) data at hospitalization. We examined their longitudinal association with the risk of developing asthma by age 6 years and investigated their biological characteristics by integrating the upper airway mRNA and microRNA data in a subset (n=182). Results: In infants hospitalized for bronchiolitis, we identified 4 phenotypes: 1) tIgElowvirusRSV-high, 2) tIgElowvirusRSV-low/RV, 3) tIgEhighvirusRSV-high, and 4) tIgEhighvirusRSV-low/RV phenotypes. Compared to phenotype 1 infants (resembling "classic" bronchiolitis), phenotype 4 infants (tIgEhighvirusRSV-low/RV) had a significantly higher risk for developing asthma (19% vs. 43%; adjOR, 2.93; 95% CI, 1.02-8.43; P=.046). Phenotypes 3 and 4 (tIgEhigh) had depleted type I interferon and enriched antigen presentation pathways; phenotype 4 also had depleted airway epithelium structure pathways. Conclusions: In this multicenter cohort, tIgE-virus clustering identified distinct phenotypes of infant bronchiolitis with differential risks of asthma development and unique biological characteristics.

Association between Early Childhood Vitamin D Status and Age 6-Year Lung Function among Children with a History of Severe Bronchiolitis in Infancy.

Improving lung health in children requires understanding the risk factors for decreased lung function. Our objective was to investigate the association between serum 25-hydroxyvitamin D (25(OH)D) levels and lung function in children. We analyzed data from a prospective cohort of infants hospitalized with bronchiolitis (severe bronchiolitis), a group at high risk for developing childhood asthma. Children were followed longitudinally, and 25(OH)D and spirometry testing were conducted at ages 3 and 6, respectively. We used a multivariable linear regression adjusted for race/ethnicity, annual household income, premature birth, and secondhand smoke exposure to examine the association between serum 25(OH)D level and primary outcomes (percent predicted [pp] of forced expiratory volume in the first second (FEV1) and the forced vital capacity (FVC)) and secondary outcome (FEV1pp/FVCpp). Serum 25(OH)D level and age 6 spirometry were available for 363 children. In adjusted analyses comparing the highest quintile (Q5) of serum 25(OH)D (median 37 ng/mL) to the lowest quintile (Q1; median 18 ng/mL), FEV1pp was 6% lower (p = 0.03) in Q1. Likewise, FVCpp was 7% lower (p = 0.03) in Q1. There was no difference in FEV1pp/FVCpp across the serum 25(OH)D quintiles. Compared to children with higher vitamin D status at age 3, those with lower status had decreased FEV1pp and FVCpp at 6 years.

Factors associated with mild bronchiolitis in young infants.

Objective: Bronchiolitis within the first 3 months of life is a risk factor for more severe illness. We aimed to identify characteristics associated with mild bronchiolitis in infants ≤90 days old presenting to the emergency department (ED). Methods: We conducted a secondary analysis of infants ≤90 days old with clinically diagnosed bronchiolitis using data from the 25th Multicenter Airway Research Collaboration prospective cohort study. We excluded infants with direct intensive care unit admissions. Mild bronchiolitis was defined as (1) sent home after the index ED visit and did not have a return ED visit or had a return ED visit without hospitalization, or (2) were hospitalized from the index ED visit to the inpatient floor for <24 hours. Multivariable logistic regression, adjusting for potential clustering by hospital site, was used to identify factors associated with mild bronchiolitis. Results: Of 373 infants aged ≤90 days, 333 were eligible for analysis. Of these, 155 (47%) infants had mild bronchiolitis, and none required mechanical ventilation. Adjusting for infant characteristics, clinical factors associated with mild bronchiolitis included older age (61-90 days vs 0-60 days) (odds ratio [OR] 2.72, 95% confidence interval [CI] 1.52-4.87), adequate oral intake (OR 4.48, 95% CI 2.08-9.66), and lowest ED oxygen saturation ≥94% (OR 3.12, 95% CI 1.55-6.30). Conclusions: Among infants aged ≤90 days presenting to the ED with bronchiolitis, about half had mild bronchiolitis. Mild illness was associated with older age (61-90 days), adequate oral intake, and oxygen saturation ≥94%. These predictors may help in the development of strategies to limit unnecessary hospitalization in young infants with bronchiolitis.

Recurrent wheezing phenotypes after severe bronchiolitis and progression to asthma.

Background: Recurrent wheezing, a common diagnosis after severe bronchiolitis, has multiple phenotypes of uncertain relation to childhood asthma. Objective: Among infants hospitalized for bronchiolitis, we investigated the relation of three 2020 recurrent wheezing phenotypes by age 4 years to asthma by age 6 years. Methods: In a 17-center cohort study of infants hospitalized with bronchiolitis, we investigated the National Heart, Lung, and Blood Institute (NHLBI) 2020-defined recurrent wheezing phenotype and 2 additional phenotypes based on this definition: multitrigger and severe. As a sensitivity analysis, we examined the NHLBI 2007 recurrent wheezing phenotype. We calculated the proportion of study subjects who developed asthma by age 6 years and used multivariable logistic regression to examine characteristics associated with the highest-risk 2020 phenotype. Results: Of 921 infants, 632 (69%) developed NHLBI 2020 recurrent wheezing, 734 (80%) developed multitrigger wheezing, and 165 (18%) developed severe wheezing by age 4 years; in addition, 296 (32%) developed NHLBI 2007-defined recurrent wheezing by age 3 years. Of 862 children with sufficient data (94%), 239 (28%) developed asthma by age 6 years. The proportions of children who progressed to asthma were as follows: 33% of those with NHLBI 2020-defined wheezing, 33% of those with multitrigger wheezing, 54% of those with severe wheezing, and 52% of those with NHLBI 2007-defined recurrent wheezing. The children with the severe phenotype who developed asthma had the associated characteristics preterm birth, child eczema, maternal asthma, and non-respiratory syncytial virus infection. Conclusion: Most infants with severe bronchiolitis developed the NHLBI 2020-defined recurrent wheezing phenotype by age 4 years. Depending on the phenotype, 33% to 54% will develop asthma by age 6 years. Future research will examine whether earlier treatment of high-risk phenotypes will improve wheezing symptoms and potentially prevent childhood asthma. (J Allergy Clin Immunol Global 2023;2:84-7.).

Integrated relationship of nasopharyngeal airway host response and microbiome associates with bronchiolitis severity.

Bronchiolitis is a leading cause of infant hospitalizations but its immunopathology remains poorly understood. Here we present data from 244 infants hospitalized with bronchiolitis in a multicenter prospective study, assessing the host response (transcriptome), microbial composition, and microbial function (metatranscriptome) in the nasopharyngeal airway, and associate them with disease severity. We investigate individual associations with disease severity identify host response, microbial taxonomical, and microbial functional modules by network analyses. We also determine the integrated relationship of these modules with severity. Several modules are significantly associated with risks of positive pressure ventilation use, including the host-type I interferon, neutrophil/interleukin-1, T cell regulation, microbial-branched-chain amino acid metabolism, and nicotinamide adenine dinucleotide hydrogen modules. Taken together, we show complex interplays between host and microbiome, and their contribution to disease severity.

Association of Nasopharyngeal and Serum Glutathione Metabolism with Bronchiolitis Severity and Asthma Risk: A Prospective Multicenter Cohort Study.

Infants hospitalized for bronchiolitis are at high risk for asthma. Glutathione-related metabolites may antagonize oxidative stress, which induces airway injuries in respiratory infection and subsequent airway remodeling. However, little is known about the relationship of glutathione-related metabolites with bronchiolitis severity and the risk of asthma. In a multicenter prospective observational cohort study of infants hospitalized for bronchiolitis, we measured nasopharyngeal and serum glutathione-related metabolites by using liquid chromatography−tandem mass spectrometry. We then examined their association with bronchiolitis severity (defined by positive pressure ventilation (PPV) use). We also identified severity-related glutathione-related metabolite signatures and examined their association with asthma at age 6 years. In 1013 infants, we identified 12 nasopharyngeal and 10 serum glutathione-related metabolites. In the multivariable models, lower relative abundances of seven metabolites, e.g., substrates of glutathione, including cysteine (adjOR 0.21, 95%CI 0.06−0.76), glycine (adjOR 0.25, 95%CI 0.07−0.85), and glutamate (adjOR 0.25, 95%CI 0.07−0.88), were significantly associated with PPV use (all FDR < 0.05). These associations were consistent with serum glutathione-related metabolites. The nasopharyngeal glutathione-related metabolite signature was also associated with a significantly higher risk of asthma (adjOR 0.90, 95%CI 0.82−0.99, p = 0.04). In infants hospitalized for bronchiolitis, glutathione-related metabolites were associated with bronchiolitis severity and asthma risk.

Proteomics endotyping of infants with severe bronchiolitis and risk of childhood asthma.

BACKGROUND: Bronchiolitis is the leading cause of hospitalization in U.S. infants and a major risk factor for childhood asthma. Growing evidence supports clinical heterogeneity within bronchiolitis. We aimed to identify endotypes of infant bronchiolitis by integrating clinical, virus, and serum proteome data, and examine their relationships with asthma development. METHODS: This is a multicenter prospective cohort study of infants hospitalized for physician-diagnosis of bronchiolitis. We identified bronchiolitis endotypes by applying unsupervised machine learning (clustering) approaches to integrated clinical, virus (respiratory syncytial virus [RSV], rhinovirus [RV]), and serum proteome data measured at hospitalization. We then examined their longitudinal association with the risk for developing asthma by age 6 years. RESULTS: In 140 infants hospitalized with bronchiolitis, we identified three endotypes: (1) clinicalatopic virusRV proteomeNFκB-dysregulated , (2) clinicalnon-atopic virusRSV/RV proteomeTNF-dysregulated , and (3) clinicalclassic virusRSV proteomeNFκB/TNF-regulated endotypes. Endotype 1 infants were characterized by high proportion of IgE sensitization and RV infection. These endotype 1 infants also had dysregulated NFκB pathways (FDR < 0.001) and significantly higher risks for developing asthma (53% vs. 22%; adjOR 4.04; 95% CI, 1.49-11.0; p = 0.006), compared with endotype 3 (clinically resembling "classic" bronchiolitis). Likewise, endotype 2 infants were characterized by low proportion of IgE sensitization and high proportion of RSV or RV infection. These endotype 2 infants had dysregulated tumor necrosis factor (TNF)-mediated signaling pathway (FDR <0.001) and significantly higher risks for developing asthma (44% vs. 22%; adjOR 2.71; 95% CI, 1.03-7.11, p = 0.04). CONCLUSION: In this multicenter cohort, integrated clustering of clinical, virus, and proteome data identified biologically distinct endotypes of bronchiolitis that have differential risks of asthma development.

Nasopharyngeal airway dual-transcriptome of infants with severe bronchiolitis and risk of childhood asthma: A multicenter prospective study.

BACKGROUND: Severe bronchiolitis (ie, bronchiolitis requiring hospitalization) during infancy is a major risk factor for childhood asthma. However, the exact mechanism linking these common conditions remains unclear. OBJECTIVES: This study sought to examine the integrated role of airway microbiome (both taxonomy and function) and host response in asthma development in this high-risk population. METHODS: This multicenter prospective cohort study of 244 infants with severe bronchiolitis (median age, 3 months) examined the infants' nasopharyngeal metatranscriptomes (microbiomes) and transcriptomes (hosts), as well as metabolomes at hospitalization. The longitudinal relationships investigated include (1) major bacterial species (Streptococcus pneumoniae, Haemophilus influenzae, and Moraxella catarrhalis), (2) microbial function, and (3) host response with risks of developing asthma by age 6 years. RESULTS: First, the abundance of S pneumoniae was associated with greater risks of asthma (P = .01), particularly in infants with nonrhinovirus infection (Pinteraction = .04). Second, of 328 microbial functional pathways that are differentially enriched by asthma development, the top pathways (eg, fatty acid and glycolysis pathways; false discovery rate [FDR] < 1 × 10-12) were driven by these 3 major species (eg, positive association of S pneumoniae with glycolysis; FDR < 0.001). These microbial functional pathways were validated with the parallel metabolome data. Third, 104 transcriptome pathways were differentially enriched (FDR < .05)-for example, downregulated interferon-α and -γ and upregulated T-cell activation pathways. S pneumoniae was associated with most differentially expressed transcripts (eg, DAGLB; FDR < 0.05). CONCLUSIONS: By applying metatranscriptomic, transcriptomic, and metabolomic approaches to a multicenter cohort of infants with bronchiolitis, this study found an interplay between major bacterial species, their function, and host response in the airway, and their longitudinal relationship with asthma development.

Severe bronchiolitis profiles and risk of asthma development in Finnish children.

BACKGROUND: Recent studies support the existence of several entities under the clinical diagnosis of bronchiolitis. Among infants with severe bronchiolitis, distinct profiles have been differentially associated with development of recurrent wheezing by age 3 years. However, their associations with actual asthma remain unclear. OBJECTIVE: Our aim was to study the association between severe bronchiolitis profiles identified by using a clustering approach and childhood asthma. METHODS: Among 408 children (aged <2 years) hospitalized with bronchiolitis in Finland (in 2008-2010), latent class analysis identified 3 bronchiolitis profiles: profile A (47%), characterized by history of wheezing and/or eczema, wheezing during acute illness, and rhinovirus infection; profile BC (38%), characterized by severe illness and respiratory syncytial virus infection; and profile D (15%), characterized by the least severely ill children, including mostly children without wheezing and with rhinovirus infection. The children were followed by questionnaire 4 years later (86% [n = 348]) and through a nationwide social insurance database 7 years later (99% [n = 403]). Current asthma at the 4- and 7-year follow-ups was defined by regular use (according to parental report and medical records) or purchase (according to the social insurance database) of asthma control medication. RESULTS: Compared with risk of current asthma associated with profile BC, we observed increased risk of current asthma associated with profile A both at the 4-year follow-up (age- and sex-adjusted odds ratio = 2.42 [95% CI = 1.23-4.75]) and at the 7-year follow-up (age- and sex-adjusted odds ratio = 3.14 [95% CI = 1.33-7.42]). No significant difference in asthma risk was observed between profile D and profile BC. CONCLUSION: These longitudinal results provide further support for an association between a distinct severe bronchiolitis profile (characterized by a history of wheezing and/or eczema and rhinovirus infection) and risk of development childhood asthma.

Urinary Tract Infections in Children with Vesicoureteral Reflux Are Accompanied by Alterations in Urinary Microbiota and Metabolome Profiles.

Children with vesicoureteral reflux (VUR) are at an increased risk of recurrent urinary tract infections (UTIs) and renal scarring. Gut microbiota are associated with disease phenotypes, but there has been no study that associates urinary microbiota (uMB) and metabolic profiles with VUR pathology. To identify dominant uMB genera and metabolites associated with UTIs in VUR, urine samples collected under sterile conditions underwent 16S ribosomal RNA sequencing (n = 49) and metabolomic analysis by mass spectrometry (n = 96). Alterations in uMB and metabolomic profiles in VUR patients suggest remodeling of urinary bacterial communities after UTIs: Dorea- and Escherichia-dominant uMB profiles were more frequently identified in participants with VUR. Prevotella- and Lactobacillus-dominant uMB profiles were more prevalent in controls (p < 0.001). Microbial composition varied based on recurrent febrile UTI status (p = 0.001). A total of 243 urinary metabolites involved in energy, amino acid, nucleotide, and lipid metabolism were altered in VUR patients with UTIs (p < 0.05). Importantly, VUR specimens revealed changes in the bacteria-associated metabolic pathways such as glutamate degradation, methyl-citrate cycle, and bile acid metabolism. PATIENT SUMMARY: Differences in urinary commensal bacteria and metabolites exist between children with and without vesicoureteral reflux (VUR). These changes may be utilized to identify patients at risk of VUR-associated kidney damage.