Global burden of acute lower respiratory infections due to respiratory syncytial virus in young children: a systematic review and meta-analysis

Wastewater surveillance together with metaviromic data revealed the unusual resurgence of infectious diseases after the first wave of the COVID-19 outbreak

How to address public health priorities after COVID-19 is becoming a critical task. To this end, we conducted wastewater surveillance for six leading pathogens, namely, SARS-CoV-2, norovirus, rotavirus, influenza A virus (IAV), enteroviruses and respiratory syncytial virus (RSV), in Nanchang city from January to April 2023. Metaviromic sequencing was conducted at the 1st, 4th, 7th, 9th, 12th and 14th weeks to reveal the dynamics of viral pathogens that were not covered by qPCR. Amplicon sequencing of the conserved region of norovirus GI and GII and the rotavirus and region encoding nonstructural protein of RSV was also conducted weekly. The results showed that after a rapid decrease in SARS-CoV-2 sewage concentrations occurred in January 2023, surges of norovirus, rotavirus, IAV and RSV started at the 6th, 7th, 8th and 11th weeks, respectively. The dynamics of the sewage concentrations of norovirus, rotavirus, IAV and RSV were consistent with the off-season resurgence of the above infectious diseases. Notably, peak sewage concentrations of norovirus GI, GII, rotavirus, IAV and RSV were found at the 6th, 3rd, 7th, 7th and 8th weeks, respectively. Astroviruses also resurge after the 7th week, as revealed by metaviromic data, suggesting that wastewater surveillance together with metaviromic data provides an essential early warning tool for revealing patterns of infectious disease resurgence.

Risk Analysis of Respiratory Syncytial Virus Among Infants in the United States by Birth Month

BACKGROUND

Respiratory syncytial virus (RSV) is a major cause of morbidity and mortality among US infants. A child's calendar birth month determines their age at first exposure(s) to RSV. We estimated birth month-specific risk of medically attended (MA) RSV lower respiratory tract infection (LRTI) among infants during their first RSV season and first year of life (FYOL).

METHODS

We analyzed infants born in the USA between July 2016 and February 2020 using three insurance claims databases (two commercial, one Medicaid). We classified infants' first MA RSV LRTI episode by the highest level of care incurred (outpatient, emergency department, or inpatient), employing specific and sensitive diagnostic coding algorithms to define index RSV diagnoses. In our main analysis, we focused on infants' first RSV season. In our secondary analysis, we compared the risk of MA RSV LRTI during infants' first RSV season to that of their FYOL.

RESULTS

Infants born from May through September generally had the highest risk of first-season MA RSV LRTI-approximately 6-10% under the specific RSV index diagnosis definition and 16-26% under the sensitive. Infants born between October and December had the highest risk of RSV-related hospitalization during their first season. The proportion of MA RSV LRTI events classified as inpatient ranged from 9% to 54% (specific) and 5% to 33% (sensitive) across birth month and comorbidity group. Through the FYOL, the overall risk of MA RSV LRTI is comparable across birth months within each claims database (6-11% under the specific definition, 17-30% under the sensitive), with additional cases progressing to care at outpatient or ED settings.

CONCLUSIONS

Our data support recent national recommendations for the use of nirsevimab in the USA. For infants born at the tail end of an RSV season who do not receive nirsevimab, a dose administered prior to the onset of their second RSV season could reduce the incidence of outpatient- and ED-related events.

Network analysis reveals age- and virus-specific circuits in nasal epithelial cells of extremely premature infants

BACKGROUND AND OBJECTIVES

Viral respiratory infections significantly affect young children, particularly extremely premature infants, resulting in high hospitalization rates and increased health-care burdens. Nasal epithelial cells, the primary defense against respiratory infections, are vital for understanding nasal immune responses and serve as a promising target for uncovering underlying molecular and cellular mechanisms.

METHODS

Using a trans-well pseudostratified nasal epithelial cell system, we examined age-dependent developmental differences and antiviral responses to influenza A and respiratory syncytial virus through systems biology approaches.

RESULTS

Our studies revealed differences in innate-receptor repertoires, distinct developmental pathways, and differentially connected antiviral network circuits between neonatal and adult nasal epithelial cells. Consensus network analysis identified unique and shared cellular-viral networks, emphasizing highly relevant virus-specific pathways, independent of viral replication kinetics.

CONCLUSION

This research highlights the importance of nasal epithelial cells in innate antiviral immune responses and offers crucial insights that allow for a deeper understanding of age-related differences in nasal epithelial cell immunity following respiratory virus infections.

Virus neutralization assays for human respiratory syncytial virus using airway organoids

Neutralizing antibodies are considered a correlate of protection against severe human respiratory syncytial virus (HRSV) disease. Currently, HRSV neutralization assays are performed on immortalized cell lines like Vero or A549 cells. It is known that assays on these cell lines exclusively detect neutralizing antibodies (nAbs) directed to the fusion (F) protein. For the detection of nAbs directed to the glycoprotein (G), ciliated epithelial cells expressing the cellular receptor CX3CR1 are required, but generation of primary cell cultures is expensive and labor-intensive. Here, we developed a high-throughput neutralization assay based on the interaction between clinically relevant HRSV grown on primary cells with ciliated epithelial cells, and validated this assay using a panel of infant sera. To develop the high-throughput neutralization assay, we established a culture of differentiated apical-out airway organoids (Ap-O AO). CX3CR1 expression was confirmed, and both F- and G-specific monoclonal antibodies neutralized HRSV in the Ap-O AO. In a side-by-side neutralization assay on Vero cells and Ap-O AO, neutralizing antibody levels in sera from 125 infants correlated well, although titers on Ap-O AO were consistently lower. We speculate that these lower titers might be an actual reflection of the neutralizing antibody capacity in vivo. The organoid-based neutralization assay described here holds promise for further characterization of correlates of protection against HRSV disease.

Nasal cathelicidin is expressed in early life and is increased during mild, but not severe respiratory syncytial virus infection

Respiratory syncytial virus is the major cause of acute lower respiratory tract infections in young children, causing extensive mortality and morbidity globally, with limited therapeutic or preventative options. Cathelicidins are innate immune antimicrobial host defence peptides and have antiviral activity against RSV. However, upper respiratory tract cathelicidin expression and the relationship with host and environment factors in early life, are unknown. Infant cohorts were analysed to characterise early life nasal cathelicidin levels, revealing low expression levels in the first week of life, with increased levels at 9 months which are comparable to 2-year-olds and healthy adults. No impact of prematurity on nasal cathelicidin expression was observed, nor were there effects of sex or birth mode, however, nasal cathelicidin expression was lower in the first week-of-life in winter births. Nasal cathelicidin levels were positively associated with specific inflammatory markers and demonstrated to be associated with microbial community composition. Importantly, levels of nasal cathelicidin expression were elevated in infants with mild RSV infection, but, in contrast, were not upregulated in infants hospitalised with severe RSV infection. These data suggest important relationships between nasal cathelicidin, upper airway microbiota, inflammation, and immunity against RSV infection, with interventional potential.

Respiratory syncytial virus NS1 inhibits anti-viral Interferon-α-induced JAK/STAT signaling, by limiting the nuclear translocation of STAT1

Human respiratory viruses are the most prevalent cause of disease in humans, with the highly infectious RSV being the leading cause of infant bronchiolitis and viral pneumonia. Responses to type I IFNs are the primary defense against viral infection. However, RSV proteins have been shown to antagonize type I IFN-mediated antiviral innate immunity, specifically dampening intracellular IFN signaling. Respiratory epithelial cells are the main target for RSV infection. In this study, we found RSV-NS1 interfered with the IFN-α JAK/STAT signaling pathway of epithelial cells. RSV-NS1 expression significantly enhanced IFN-α-mediated phosphorylation of STAT1, but not pSTAT2; and neither STAT1 nor STAT2 total protein levels were affected by RSV-NS1. However, expression of RSV-NS1 significantly reduced ISRE and GAS promoter activity and anti-viral IRG expression. Further mechanistic studies demonstrated RSV-NS1 bound STAT1, with protein modeling indicating a possible interaction site between STAT1 and RSV-NS1. Nuclear translocation of STAT1 was reduced in the presence of RSV-NS1. Additionally, STAT1's interaction with the nuclear transport adapter protein, KPNA1, was also reduced, suggesting a mechanism by which RSV blocks STAT1 nuclear translocation. Indeed, reducing STAT1's access to the nucleus may explain RSV's suppression of IFN JAK/STAT promoter activation and antiviral gene induction. Taken together these results describe a novel mechanism by which RSV controls antiviral IFN-α JAK/STAT responses, which enhances our understanding of RSV's respiratory disease progression.

Effectiveness of high flow nasal Cannula (HFNC) therapy compared to standard oxygen therapy (SOT) and continuous positive airway pressure (CPAP) in bronchiolitis

High Flow Nasal Cannula therapy (HFNC) is a form of respiratory support for bronchiolitis. Recent evidence confirms HFNC reduces the risk of treatment escalation by nearly half (45%) compared to standard oxygen therapy (SOT), although most patients (75%) with mild-moderate respiratory distress manage well on SOT. The majority of children (60%) failing SOT respond well to HFNC making rescue use of HFNC a more cost-effective approach compared to its first-line use. HFNC is compared toCPAP in the setting of moderate to severe bronchiolitis. Patients on HFNC have a slightly elevated risk of treatment failure especially in severe bronchiolitis, but this does not translate to a significant difference in patient or healthcare centred outcomes. HFNC has improved tolerance, a lower complication rate and is more easily available in peripheral hospitals. It is therefore the preferred first line option followed by rescue CPAP. HFNC is clinically effective and safe to use in bronchiolitis of all severities.

Longitudinal humoral analysis in RSV-infected infants identifies pre-existing RSV strain-specific G and evolving cross-reactive F antibodies

Respiratory syncytial virus (RSV) is among the most common causes of lower respiratory tract infection (LRTI) and hospitalization in infants. However, the mechanisms of immune control in infants remain incompletely understood. Antibody profiling against attachment (G) and fusion (F) proteins in children less than 2 years of age, with mild (outpatients) or severe (inpatients) RSV disease, indicated substantial age-dependent differences in RSV-specific immunity. Maternal antibodies were detectable for the first 3 months of life, followed by a long window of immune vulnerability between 3 and 6 months and a rapid evolution of FcγR-recruiting immunity after 6 months of age. Acutely ill hospitalized children exhibited lower G-specific antibodies compared with healthy controls. With disease resolution, RSV-infected infants generated broad functional RSV strain-specific G-responses and evolved cross-reactive F-responses, with minimal maternal imprinting. These data suggest an age-independent RSV G-specific functional humoral correlate of protection, and the evolution of RSV F-specific functional immunity with disease resolution.

Impact of Nirsevimab Immunization on Pediatric Hospitalization Rates: A Systematic Review and Meta-Analysis (2024)

A systematic review with a meta-analysis was performed to gather available evidence on the effectiveness of monoclonal antibody nirsevimab in the prevention of lower respiratory tract diseases (LRTDs) due to respiratory syncytial virus (RSV) in children and newborns (CRD42024540669). Studies reporting on real-world experience and randomized controlled trials (RCTs) were searched for in three databases (PubMed, Embase, and Scopus) until 1 May 2024. Our analysis included five RCTs, seven real-world reports, and one official report from the health authorities. Due to the cross-reporting of RCTs and the inclusion of multiple series in a single study, the meta-analysis was performed on 45,238 infants from 19 series. The meta-analysis documented a pooled immunization efficacy of 88.40% (95% confidence interval (95% CI) from 84.70 to 91.21) on the occurrence of hospital admission due to RSV, with moderate heterogeneity (I2 24.3%, 95% CI 0.0 to 56.6). Immunization efficacy decreased with the overall length of the observation time (Spearman's r = -0.546, p = 0.016), and the risk of breakthrough infections was substantially greater in studies with observation times ≥150 days compared to studies lasting <150 days (risk ratio 2.170, 95% CI 1.860 to 2.532). However, the effect of observation time in meta-regression analysis was conflicting (β = 0.001, 95% CI -0.001 to 0.002; p = 0.092). In conclusion, the delivery of nirsevimab was quite effective in preventing hospital admissions due to LRTDs. However, further analyses of the whole RSV season are required before tailoring specific public health interventions.

Disease Severity and Cytokine Expression in the Rhinovirus-Induced First Wheezing Episode

Wheezing children infected with rhinovirus (RV) have a markedly increased risk of subsequently developing recurrencies and asthma. No previous studies have assessed the association between cytokine response and the severity of acute illness in the first wheezing episode in children infected with RV. Forty-seven children treated both as inpatients and as outpatients infected with RV only, aged 3-23 months, with severe first wheezing episodes were recruited. During acute illness, peripheral blood mononuclear cells (PBMCs) were isolated and stimulated with anti-CD3/anti-CD28 in vitro. A multiplex ELISA was used to quantitatively identify 56 different cytokines. The mean age of the children was 17 months, 74% were males, 79% were hospitalized, and 33% were sensitized. In adjusted analyses, the inpatient group was characterized by decreased expressions of interferon gamma (IFN-γ), interleukin 10 (IL-10), macrophage inflammatory protein 1 alpha (MIP-1α), RANTES (CCL5), and tumor necrosis factor-alpha (TNF-α) and an increased expression of ENA-78 (CXCL5) compared to the outpatient group. The cytokine response profiles from the PBMCs were different between the inpatient and outpatient groups. Our results support that firmly controlled interplay between pro-inflammatory and anti-inflammatory responses are required during acute viral infection to absolve the initial infection leading, to less severe illness.

The imbalance of pulmonary Th17/Treg cells in BALB/c suckling mice infected with respiratory syncytial virus-mediated intestinal immune damage and gut microbiota changes

The immune response induced by respiratory syncytial virus (RSV) infection is closely related to changes in the composition and function of gastrointestinal microorganisms. However, the specific mechanism remains unknown and the pulmonary-intestinal axis deserves further study. In this study, the mRNA levels of ROR-γt and Foxp3 in the lung and intestine increased first and then decreased. IL-17 and IL-22 reached the maximum on the third day after infection in the lung, and on the second day after infection in the small intestine and colon, respectively. RegⅢγ in intestinal tissue reached the maximum on the third day after RSV infection. Moreover, the genus enriched in the RSV group was Aggregatibacter, and Proteus was reduced. RSV infection not only causes Th17/Treg cell imbalance in the lungs of mice but also leads to the release of excessive IL-22 from the lungs through blood circulation which binds to IL-22 receptors on the intestinal surface, inducing RegⅢγ overexpression, impaired intestinal Th17/Treg development, and altered gut microbiota composition. Our research reveals a significant link between the pulmonary and intestinal axis after RSV infection.

IMPORTANCE

RSV is the most common pathogen causing acute lower respiratory tract infections in infants and young children, but the complex interactions between the immune system and gut microbiota induced by RSV infection still requires further research. In this study, it was suggested that RSV infection in 7-day-old BALB/c suckling mice caused lung inflammation and disruption of Th17/Treg cells development, and altered the composition of gut microbiota through IL-22 induced overexpression of RegⅢγ, leading to intestinal immune injury and disruption of gut microbiota. This research reveals that IL-22 may be the link between the lung and gut. This study may provide a new insight into the intestinal symptoms caused by RSV and other respiratory viruses and the connection between the lung and gut axis, as well as new therapeutic ideas for the treatment of RSV-infected children.

Updates on respiratory syncytial virus prophylaxis: the past, present and future

PURPOSE OF REVIEW

Human respiratory syncytial virus (RSV) causes acute respiratory infection in individuals of all age groups. It is the most common pathogen identified in infants and young children with acute lower respiratory infection. Although most infants and young children experience mild, cold-like symptoms, some infants develop severe lower respiratory tract disease such as pneumonia and bronchiolitis that may result in an emergency department visit or hospitalization.

RECENT FINDINGS

In the United States, hospitalization rates have risen during the last decades, and while premature infants with chronic lung disease and congenital heart disease are at increased risk for severe presentations, the majority of hospitalizations occur in previously healthy infants. Until recently, RSV prophylaxis was only available for former preterm infants and those with certain underlying medical conditions.

SUMMARY

The need for preventive interventions against RSV is crucial. This paper will provide a review of the vaccine development, the spectrum of RSV prophylaxis, current challenges associated with the cost, insurance coverage and equitable distribution of targeted therapies.

Analysis of the prevalence and clinical features of respiratory syncytial virus infection in a pediatric hospital in Zhejiang Province from 2019 to 2023

The aim of this study was to investigate the epidemiological characteristics of respiratory syncytial virus (RSV) infections in children in Zhejiang from 2019 to 2023. Data from pediatric patients who visited the Children's Hospital of Zhejiang University School of Medicine for RSV infection between 2019 and 2023 were analyzed. Nasopharyngeal swabs were collected for RSV antigen detection, and relevant patient information was collected. Factors such as age were analyzed. A total of 673 094 specimens were included from 2019 to 2023, with a rate of positive specimens of 4.74% (31 929/673 094). The highest rate of positive specimens of 10.82%, was recorded in 2021, while the remaining years had a rate of approximately 3%-5%. In terms of seasonal prevalence characteristics, the rate of positive specimens in 2019, 2020, and 2022 peaked in the winter months at approximately 8% and decreased in the summer months, where the rate of positive specimens remained at approximately 0.5%. In contrast, summer is the peak period for RSV incidence in 2021 and 2023, with the rate of positive specimens being as high as 9%-12%. Based on the prevalence characteristics of gender and age, this study found that the detection rate of positive specimens was higher in boys than in girls in 2019-2023. In 2019-2022, among the different age groups, the highest rate of positive specimens was found in children aged 0 to <6 months, and it decreased with age. In 2023, the rate of positive specimens was above 8% in the 0 to <6 months, 6 to <12 months, and 1-2 years age groups, with the highest rate of positive specimens in the 1-2 years age group, and a gradual decrease in the rate of positive specimens with age for children over 3 years of age. Between 2019 and 2023, the epidemiological pattern of RSV changed. A summer peak was observed in 2021 and 2023.

RSV Infection in Refugees and Asylum Seekers: A Systematic Review and Meta-Analysis

Respiratory diseases, including respiratory syncytial virus (RSV) infections, are common reasons for seeking healthcare among refugees and asylum seekers. A systematic review with meta-analysis was designed to appraise all the available evidence on RSV infections among individuals in refugee camps. Three medical databases (PubMed, Embase, and Scopus) as well as the preprint repository medRxiv.org were searched for eligible observational studies, and the collected cases were pooled in a random-effects meta-analysis model. Heterogeneity was assessed using the I2 statistics. Funnel plots and a regression analysis were calculated for analyzing reporting bias. Eventually, six studies were retrieved from three areas (Bangladesh, Thailand, and Kenya), with pooled estimates of 129.704 cases per 1000 samples (95% CI 66.393 to 237.986) for RSV compared to 110.287 per 1000 people for influenza A (95% CI 73.186 to 162.889), 136.398 cases per 1000 people (95% CI 84.510 to 212.741) for human adenovirus (HAdV), 69.553 per 1000 people (95% CI 49.802 to 96.343) for parainfluenzavirus (PIFV), and 60.338 per 1000 people (95% CI 31.933 to 111.109) for human metapneumovirus (hMPV). Using influenza A as a reference group, the risk for a positive specimen was greater for RSV (relative risk [RR] 1.514, 95% CI 1.396 to 1.641) and HAdV (RR 1.984, 95% CI 1.834 to 2.146) and lower for influenza B (RR 0.276, 95% CI: 0.239 to 0.319), PIFV (RR: 0.889, 95% CI 0.806 to 0.981), and hMPV (RR 0.594, 95% CI 0.534 to 0.662). In summary, high rates of RSV infections were documented among individuals sheltered in refugee camps, stressing the importance of specifically designed preventive strategies.

Biotechnological potential of actinomycetes in the 21st century: a brief review

This brief review aims to draw attention to the biotechnological potential of actinomycetes. Their main uses as sources of antibiotics and in agriculture would be enough not to neglect them; however, as we will see, their biotechnological application is much broader. Far from intending to exhaust this issue, we present a short survey of the research involving actinomycetes and their applications published in the last 23 years. We highlight a perspective for the discovery of new active ingredients or new applications for the known metabolites of these microorganisms that, for approximately 80 years, since the discovery of streptomycin, have been the main source of antibiotics. Based on the collected data, we organize the text to show how the cosmopolitanism of actinomycetes and the evolutionary biotic and abiotic ecological relationships of actinomycetes translate into the expression of metabolites in the environment and the richness of biosynthetic gene clusters, many of which remain silenced in traditional laboratory cultures. We also present the main strategies used in the twenty-first century to promote the expression of these silenced genes and obtain new secondary metabolites from known or new strains. Many of these metabolites have biological activities relevant to medicine, agriculture, and biotechnology industries, including candidates for new drugs or drug models against infectious and non-infectious diseases. Below, we present significant examples of the antimicrobial spectrum of actinomycetes, which is the most commonly investigated and best known, as well as their non-antimicrobial spectrum, which is becoming better known and increasingly explored.

Viral load in hospitalized infants with respiratory syncytial virus bronchiolitis: a three-way comparative analysis

Viral load measurement of Respiratory syncytial virus (RSV) in acute bronchiolitis depends on specimen collection, viral load quantification, and transport media. The aim of this study was to investigate viral load in three-way-comparative analyses; nasal swab versus nasal wash, quantitative real-time polymerase chain reaction (RT-PCR) versus cell tissue culture, and various transport media. A prospective cohort study of infants aged < 12 months, admitted to the Soroka Medical Center, due to acute bronchiolitis, was conducted. Two nasal swabs and two nasal wash samples (in UTM and VCM) were collected from each infant upon admission and after 48 h. Samples were immediately stored at -80 °C and tested at Viroclinics DDL (Rotterdam, Netherlands). Quantitative RT-PCR and quantitative virus culture were performed using tissue culture infective dose (TCID50). Spearman's correlation coefficient test assessed the correlation between the different methods, viral load, and clinical severity score. One hundred samples were collected from 13 infants (mean age 5.7 ± 3.8 months, 46% males). Twelve patients were RSV-A positive, and one was RSV-B positive. A high correlation was found between transport media- UTM and VCM (0.92, P < 0.001) and between nasal swabs and nasal wash samples (0.62, P = 0.02). RSV signals were higher in nasal wash than in swabs. PCR signals were lower in the second collection compared to the first. No correlation was found between viral load and clinical severity.    Conclusion: RSV viral load is comparable across nasal wash, nasal swabs, and various transport media. However, it did not correlate with clinical severity, probably due to the limited sample size. Broader analyses are warranted. What is Known: • Viral load measurement in Respiratory Syncytial Virus (RSV) bronchiolitis depends on specimen collection, viral load quantification, and transport media. • The COVID-19 pandemic underscored the paramount significance of proper specimen collection, notably through nasal swabs. What is New: • RSV viral load was investigated in three-way-comparative analyses. • RSV viral load correlated well across PCR and tissue culture, nasal wash and swabs, and various transport media. RSV viral load did not correlate with clinical severity.

Respiratory Syncytial Virus Vaccine Design Using Structure-Based Machine-Learning Models

When designing live-attenuated respiratory syncytial virus (RSV) vaccine candidates, attenuating mutations can be developed through biologic selection or reverse-genetic manipulation and may include point mutations, codon and gene deletions, and genome rearrangements. Attenuation typically involves the reduction in virus replication, due to direct effects on viral structural and replicative machinery or viral factors that antagonize host defense or cause disease. However, attenuation must balance reduced replication and immunogenic antigen expression. In the present study, we explored a new approach in order to discover attenuating mutations. Specifically, we used protein structure modeling and computational methods to identify amino acid substitutions in the RSV nonstructural protein 1 (NS1) predicted to cause various levels of structural perturbation. Twelve different mutations predicted to alter the NS1 protein structure were introduced into infectious virus and analyzed in cell culture for effects on viral mRNA and protein expression, interferon and cytokine expression, and caspase activation. We found the use of structure-based machine learning to predict amino acid substitutions that reduce the thermodynamic stability of NS1 resulted in various levels of loss of NS1 function, exemplified by effects including reduced multi-cycle viral replication in cells competent for type I interferon, reduced expression of viral mRNAs and proteins, and increased interferon and apoptosis responses.

Neutrophil responses to RSV infection show differences between infant and adult neutrophils

INTRODUCTION

Respiratory syncytial virus (RSV) causes a severe respiratory condition, bronchiolitis, in infants but not in adults. Bronchiolitis is characterised by neutrophilic infiltration in the airways, but whether neutrophils enhance recovery from infection or contribute to its pathology remains unknown.

METHODS

We used a novel in-vitro model to compare term umbilical cord blood (infant) (n=17 donors) and adult neutrophils (n=15 donors) during migration across RSV-infected differentiated human nasal airway epithelial cells (AECs) in a basolateral to apical direction.

RESULTS

Greater numbers of infant neutrophils (mean (95% CI)) (336 684 (242 352 to 431 015)) migrated across RSV-infected AECs to the apical compartment (equivalent to the airway lumen) compared with adult neutrophils (56 586 (24 954 to 88 218)) (p<0.0001). Having reached the apical compartment of infected AECs, much greater numbers of infant neutrophils (140 787 (103 117 to 178 456)) became apoptotic compared with adult (5853 (444 to 11 261)) (p=0.002). Infant neutrophils displayed much greater expression of CD11b, CD64, neutrophil elastase (NE) and myeloperoxidase (MPO) than adult neutrophils at baseline and at all points of migration. However, as adult neutrophils migrated, expression of CD11b, CD64, NE and MPO became greater than at baseline.

DISCUSSION

The high proportion of infant neutrophils migrating across RSV-infected AECs correlates with the neutrophilic infiltrate seen in infants with severe RSV bronchiolitis, with large numbers undergoing apoptosis, which may represent a protective mechanism during infection. Compared with adult neutrophils, infant neutrophils already have high expression of surface markers before contact with AECs or migration, with less capacity to increase further in response to RSV infection or migration.

Where Birth Month, Sex and Age Matters: The Burden of Severe Respiratory Disease in Danish Children <5 Years, 2016-2022

BACKGROUND

In light of the substantial impact that respiratory diseases in young children poses on healthcare systems globally, and in the wake of the recent COVID-19 pandemic, there is a growing urgency to obtain reliable estimates on the burden of respiratory disease.

OBJECTIVES

The aim of this study is to quantify the overall burden of respiratory disease requiring hospitalizations and explore the trends in these admissions in Danish children <5 years, January 1, 2016-October 31, 2022.

METHODS

The number of hospitalizations attributed to respiratory infections in children <5 years, was extracted from the Danish National Patient Register, and stratified into subgroups based on age, gender and birth month, and presented on a month-to-month basis.

RESULTS

A total of 48,194 children under the age of 5, were hospitalized due to respiratory infections within the study period and the annual hospitalization incidence exhibited a noteworthy variation. Risk factors associated with the highest hospitalization incidence were young age, male gender and in children under 1-year-old, birth months falling in the period of November to January. Younger age and admission during the winter months were linked to longer hospital stays. The seasonal pattern of hospitalizations and the distribution of hospitalizations across various subgroups were greatly influenced by the COVID-19 pandemic.

CONCLUSION

This study describes and quantifies the importance of factoring in specific child demographics and seasonal variations in hospitalizations when devising preventive healthcare strategies such as the use of monoclonal antibody therapy and vaccines.

Efficacy of Respiratory Syncytial Virus Vaccination to Prevent Lower Respiratory Tract Illness in Older Adults: A Systematic Review and Meta-Analysis of Randomized Controlled Trials

A systematic review and meta-analysis was designed in order to ascertain the effectiveness of respiratory syncytial virus (RSV) vaccination in preventing lower respiratory tract diseases (LRTD) in older adults (age ≥ 60 years). Studies reporting on randomized controlled trials (RCTs) were searched for in three databases (PubMed, Embase, and Scopus) and the preprint repository medRxiv until 31 March 2024. A total of nine studies were eventually included, two of which were conference proceedings. Our analysis included five RCTs on five RSV vaccines (RSVpreF, RSVPreF3, Ad26.RSV.preF, MEDI7510, and mRNA-1345). The meta-analysis documented a pooled vaccine efficacy of 81.38% (95% confidence interval (95% CI) 70.94 to 88.06) for prevention of LRTD with three or more signs/symptoms during the first RSV season after the delivery of the vaccine. Follow-up data were available for RSVPreF3 (2 RSV seasons), RSVpreF (mid-term estimates of second RSV season), and mRNA-1345 (12 months after the delivery of the primer), with a pooled VE of 61.15% (95% CI 45.29 to 72.40). After the first season, the overall risk for developing RSV-related LRTD was therefore substantially increased (risk ratio (RR) 4.326, 95% CI 2.415; 7.748). However, all estimates were affected by substantial heterogeneity, as suggested by the 95% CI of I2 statistics, which could be explained by inconsistencies in the design of the parent studies, particularly when dealing with case definition. In conclusion, adult RSV vaccination was quite effective in preventing LRTD in older adults, but the overall efficacy rapidly decreased in the second season after the delivery of the vaccine. Because of the heterogenous design of the parent studies, further analyses are required before tailoring specific public health interventions.

Respiratory Syncytial Virus and Influenza Infections in Children in Ulaanbaatar, Mongolia, 2015-2021

BACKGROUND

Data available for RSV and influenza infections among children < 2 years in Mongolia are limited. We present data from four districts of Ulaanbaatar from April 2015 to June 2021.

METHODS

This study was nested in an enhanced surveillance project evaluating pneumococcal conjugate vaccine (PCV13) impact on the incidence of hospitalized lower respiratory tract infections (LRTIs). Our study was restricted to children aged < 2 years with arterial O2 saturation < 93% and children with radiological pneumonia. Nasopharyngeal (NP) swabs collected at admission were tested for RSV and influenza using qRT-PCR. NP swabs of all patients with radiological pneumonia and of a subset of randomly selected NP swabs were tested for S. pneumoniae (S.p.) by qPCR and for serotypes by culture and DNA microarray.

RESULTS

Among 5705 patients, 2113 (37.0%) and 386 (6.8%) had RSV and influenza infections, respectively. Children aged 2-6 months had a higher percentage of very severe RSV infection compared to those older than 6 months (42.2% versus 31.4%, p-value Fisher's exact = 0.001). S.p. carriage was detected in 1073/2281 (47.0%) patients. Among S.p. carriage cases, 363/1073 (33.8%) had S.p. and RSV codetection, and 82/1073 (7.6%) had S.p. and influenza codetection. S.p. codetection with RSV/influenza was not associated with more severe LRTIs, compared to only RSV/influenza cases.

CONCLUSION

In Mongolia, RSV is an important pathogen causing more severe LRTI in children under 6 months of age. Codetection of RSV or influenza virus and S.p. was not associated with increased severity.

The increase of bronchiolitis severity in the 2022-2023 season in an Italian tertiary children's hospital: An isolated phenomenon or a warning sign?

AIM

Recent literature has shown epidemiological changes in bronchiolitis with an increased incidence in the post-SARS-CoV-2 pandemic period but reports regarding disease severity are conflicting. We aimed to describe the epidemiology, disease severity, and microbiology of bronchiolitis during the 2022-2023 cold season compared to the previous 5 years.

METHODS

This single-center retrospective observational study at IRCCS Gaslini, Italy, included all children aged 0-2 years hospitalized for bronchiolitis from 1 September 2017 to 31 August 2023. Findings from the 2022-2023 season were compared to the previous 5 years.

RESULTS

We observed a statistically significant increase in the 2022-2023 season in the absolute number of bronchiolitis admissions. Children who required mechanical ventilation (MV) dramatically increased from a total of seven patients in the previous five seasons to 17 in the 2022-2023 season alone (p = .001). All other severity parameters significantly increased: the need for respiratory support (p = .002), the median length of stay (5 days vs. 4 days, p = .001), and the median duration of respiratory support (4 days vs. 3 days, p = .016).

CONCLUSIONS

We report a substantial increase in the severity of bronchiolitis in the season 2022-2023 with a remarkable number of previously healthy infants requiring MV. Further studies are needed to confirm whether our findings are an isolated phenomenon or part of a true global trend. Health systems need to be prepared and protective preventive measures should be implemented for all newborns.

Effectiveness and Safety of Palivizumab for the Prevention of Serious Lower Respiratory Tract Infection Caused by Respiratory Syncytial Virus: A Systematic Review

OBJECTIVE

 Palivizumab is a humanized monoclonal antibody approved for the prevention of serious lower respiratory tract infection (LRTI) caused by respiratory syncytial virus (RSV) in infants and young children at high risk of RSV disease. This systematic review summarized evidence on the effectiveness and safety of palivizumab when used in approved populations.

STUDY DESIGN

 A systematic review of Phase III trials and observational studies was conducted according to the population, intervention, comparator, outcome, timing, setting (PICOTS) approach (PROSPERO, CRD42021281380). Target populations consisted of infants with a history of premature birth (≤35-week gestational age) and children aged <2 years with bronchopulmonary dysplasia (BPD) or with hemodynamically significant congenital heart disease (hs-CHD). Outcomes of interest included RSV-related hospitalization, admission to intensive care unit (ICU), requirement for mechanical ventilation, treatment-related adverse events (AEs), and RSV-related deaths. Information sources were literature search (Ovid MEDLINE and Embase), pragmatic searches, and snowballing (covering the period up to 07 September 2021).

RESULTS

 A total of 60 sources were included (5 Phase III trials and 55 observational studies). RSV-related hospitalization rates following palivizumab prophylaxis in Phase III trials were 1.8% in premature infants and 7.9% in children with BPD, which were significantly lower than rates in placebo arms. In the real-world setting, similar hospitalization rates were found (0.7-4.0% in premature infants [16 studies] and 0-5.5% in patients with BPD [10 studies]) with ICU admission reported in 0 to 33.3% of patients hospitalized for RSV. In Phase III trials, RSV-related mortality rates were 0.2 and 0.3%, while AEs occurred in 11% of premature and/or BPD patients and 7.2% of hs-CHD patients, consisting mainly of injection site reaction, fever, and diarrhea. Similar results were found in observational studies.

CONCLUSION

 This systematic review supports the effectiveness and safety of palivizumab in the indicated populations.

KEY POINTS

· Systematic review supports the positive benefit-risk profile of palivizumab in the indicated populations.. · Real-world safety and effectiveness of palivizumab are consistent with Phase III trials results.. · Palivizumab reduces RSV-related hospitalizations, ICU admissions, and need for mechanical ventilation..

Global Seasonal Activities of Respiratory Syncytial Virus Before the Coronavirus Disease 2019 Pandemic: A Systematic Review

Varied seasonal patterns of respiratory syncytial virus (RSV) have been reported worldwide. We conducted a systematic review on articles identified in PubMed reporting RSV seasonality based on data collected before 1 January 2020. RSV seasonal patterns were examined by geographic location, calendar month, analytic method, and meteorological factors including temperature and absolute humidity. Correlation and regression analyses were conducted to explore the relationship between RSV seasonality and study methods and characteristics of study locations. RSV seasons were reported in 209 articles published in 1973-2023 for 317 locations in 77 countries. Regular RSV seasons were similarly reported in countries in temperate regions, with highly variable seasons identified in subtropical and tropical countries. Longer durations of RSV seasons were associated with a higher daily average mean temperature and daily average mean absolute humidity. The global seasonal patterns of RSV provided important information for optimizing interventions against RSV infection.

Novel Approach for Detecting Respiratory Syncytial Virus in Pediatric Patients Using Machine Learning Models Based on Patient-Reported Symptoms: Model Development and Validation Study

BACKGROUND

Respiratory syncytial virus (RSV) affects children, causing serious infections, particularly in high-risk groups. Given the seasonality of RSV and the importance of rapid isolation of infected individuals, there is an urgent need for more efficient diagnostic methods to expedite this process.

OBJECTIVE

This study aimed to investigate the performance of a machine learning model that leverages the temporal diversity of symptom onset for detecting RSV infections and elucidate its discriminatory ability.

METHODS

The study was conducted in pediatric and emergency outpatient settings in Japan. We developed a detection model that remotely confirms RSV infection based on patient-reported symptom information obtained using a structured electronic template incorporating the differential points of skilled pediatricians. An extreme gradient boosting-based machine learning model was developed using the data of 4174 patients aged ≤24 months who underwent RSV rapid antigen testing. These patients visited either the pediatric or emergency department of Yokohama City Municipal Hospital between January 1, 2009, and December 31, 2015. The primary outcome was the diagnostic accuracy of the machine learning model for RSV infection, as determined by rapid antigen testing, measured using the area under the receiver operating characteristic curve. The clinical efficacy was evaluated by calculating the discriminative performance based on the number of days elapsed since the onset of the first symptom and exclusion rates based on thresholds of reasonable sensitivity and specificity.

RESULTS

Our model demonstrated an area under the receiver operating characteristic curve of 0.811 (95% CI 0.784-0.833) with good calibration and 0.746 (95% CI 0.694-0.794) for patients within 3 days of onset. It accurately captured the temporal evolution of symptoms; based on adjusted thresholds equivalent to those of a rapid antigen test, our model predicted that 6.9% (95% CI 5.4%-8.5%) of patients in the entire cohort would be positive and 68.7% (95% CI 65.4%-71.9%) would be negative. Our model could eliminate the need for additional testing in approximately three-quarters of all patients.

CONCLUSIONS

Our model may facilitate the immediate detection of RSV infection in outpatient settings and, potentially, in home environments. This approach could streamline the diagnostic process, reduce discomfort caused by invasive tests in children, and allow rapid implementation of appropriate treatments and isolation at home. The findings underscore the potential of machine learning in augmenting clinical decision-making in the early detection of RSV infection.

Prevalence of Infectious Diseases in Children at Preschool Education Institutions and Stakeholder Opinions

Preschool education institutions, where children have close contact and social interactions, can serve as potential environments for the transmission of infectious diseases. This issue poses a significant health concern, impacting both individual and public well-being. Thus, the present research set out to determine the prevalence of infectious diseases in preschool children and the views of parents and teachers on the prevention of infectious diseases. The study employed a mixed-method approach and involved 397 parents and 46 preschool teachers. The study was survey-based via in-person interviews. The results revealed that after they started school (almost in 5 months), children with a mean age of 4.7 ± 0.5 years experienced illness approximately 3.5 ± 2.0 times, of whom 91.5% used antibiotics. The prevalence of infectious diseases was found to be associated with the child's being born at term, maternal education level, and the public/private status of preschool institutions. The presence of a sick child in the classroom elicits negative emotions from both teachers and parents. They recommend that studies on education, safety, hygiene, school health, health screenings, regulation of the learning environment, legal regulations, and school exclusion policies be carried out to prevent infectious diseases. When children with infectious diseases come to school, nearly half of the teachers admit them to the classroom due to various reasons and pressures. Parents request teachers to monitor medication, control sweating, and use a nebulizer for their sick children. Some of the teachers meet these requests, but they claim that the educational process is negatively affected. At preschool education institutions, the risk factors of infectious diseases have a complex structure and can be influenced by variables related to teachers, children, parents and the institution itself. Infectious diseases not only pose a threat to health but also impact teachers' and parents' emotions, teacher-child relationships, and the overall atmosphere within schools and classrooms.

Evaluation of Etiological Causes and Factors Affect Length of Hospitalization in Neonates Hospitalized with Lower Respiratory Tract Infection

Objectives

This study aims to determine the risk factors by examining the sociodemographic characteristics of infants hospitalized in the neonatal intensive care unit (NICU) due to lower respiratory tract infection (LRTI), to determine the factors that affect the duration of hospitalization, and to determine the underlying microbial factors and evaluate them in the light of the literature.

Methods

This study evaluated the data of newborns hospitalized with LTRI between 01 October 2022 and 31 March 2023. Demographic characteristics of the patients detected viral agents, duration of hospitalization and risk factors were recorded in the study form. Babies divided viral LRTI and non-viral LRTI, and then compared with each other. Additionally, the facts that might affect the duration of hospitalization were investigated.

Results

The study included 57 babies. Viral agent was detected in 50.9% of the babies, the most frequently viral agent was respiratory syncytial virus (RSV) (48.2%). Other viral factors, in order of frequency; Adenovirus, SARS-CoV-2, Influenza A and B. There is no demographic difference between the viral agent positive and negative groups. The patients were evaluated according to length of hospitalization, it was seen that the hospital stay was longer in babies who were found to be viral positive and needed oxygen therapy (p=0.02, p=0.03, respectively). The male gender ratio was higher in the group with longer hospital stays, but this difference was not statistically significant. Although the rate of exclusive breastfeeding was higher in the group with a short hospitalization period, this difference was not statistically significant (p>0.05).

Conclusion

RSV is currently the most frequently detected viral agent in lower respiratory tract infections in newborns. The hospital stay of babies diagnosed with RSV is longer than those with non-RSV viral agents. So struggling with RSV is important in preventing lower respiratory tract infections in newborns. It is necessary to develop a vaccine or immunoglobulin application against RSV infection not only for preterm babies but also for all newborn babies.

Monoclonal antibodies targeting sites in respiratory syncytial virus attachment G protein provide protection against RSV-A and RSV-B in mice

Currently, only Palivizumab and Nirsevimab that target the respiratory syncytical virus (RSV) fusion protein are licensed for pre-treatment of infants. Glycoprotein-targeting antibodies may also provide protection against RSV. In this study, we generate monoclonal antibodies from mice immunized with G proteins from RSV-A2 and RSV-B1 strains. These monoclonal antibodies recognize six unique antigenic classes (G0-G5). None of the anti-G monoclonal antibodies neutralize RSV-A2 or RSV-B1 in vitro. In mice challenged with either RSV-A2 line 19 F or RSV-B1, one day after treatment with anti-G monoclonal antibodies, all monoclonal antibodies reduce lung pathology and significantly reduce lung infectious viral titers by more than 2 logs on day 5 post-RSV challenge. RSV dissemination in the lungs was variable and correlated with lung pathology. We demonstrate new cross-protective anti-G monoclonal antibodies targeting multiple sites including conformation-dependent class G0 MAb 77D2, CCD-specific class G1 MAb 40D8, and carboxy terminus of CCD class G5 MAb 7H11, to support development of G-targeting monoclonal antibodies against RSV.

A potential bivalent mRNA vaccine candidate protects against both RSV and SARS-CoV-2 infections

As the world continues to confront severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), respiratory syncytial virus (RSV) is also causing severe respiratory illness in millions of infants, elderly individuals, and immunocompromised people globally. Exacerbating the situation is the fact that co-infection with multiple viruses is occurring, something which has greatly increased the clinical severity of the infections. Thus, our team developed a bivalent vaccine that delivered mRNAs encoding SARS-CoV-2 Omicron spike (S) and RSV fusion (F) proteins simultaneously, SF-LNP, which induced S and F protein-specific binding antibodies and cellular immune responses in BALB/c mice. Moreover, SF-LNP immunization effectively protected BALB/c mice from RSV infection and hamsters from SARS-CoV-2 Omicron infection. Notably, our study pointed out the antigenic competition problem of bivalent vaccines and provided a solution. Overall, our results demonstrated the potential of preventing two infectious diseases with a single vaccine and provided a paradigm for the subsequent design of multivalent vaccines.

Parental awareness and attitudes towards prevention of respiratory syncytial virus in infants and young children in Australia

AIM

To assess parental awareness of respiratory syncytial virus (RSV) and the level of acceptance of future RSV prevention strategies.

METHODS

A cross-sectional online survey was implemented targeting "future" and "current" parents of children aged ≤5 years in Australia.

RESULTS

From 1992 eligible participants, two non-mutually exclusive subgroups were formed: "current" parents (N = 1931) and "pregnant/planning" parents (N = 464: 403 also "current" parents and 61 "future" parents). Participants were predominantly (86.6%) aged 25-39 years and 68.5% with university education. The majority (89.6% current; 78.7% future) had heard of RSV. Of those, 64.2% (current) and 50.0% (future) were aware that pneumonia is associated with RSV; 71.8% (current) and 52.1% (future) were aware that bronchiolitis is associated with RSV. In multivariable logistic regression analyses, Australian-born parents (aOR = 2.47 [95% CI: 1.48-4.12]), living in the eastern states (e.g., New South Wales: aOR = 6.15 [95% CI:2.10-18.04]), with a university-level education (aOR = 2.61 [95% CI:1.38-4.94]) and being a current parent (aOR = 12.26 [95% CI:2.82-53.28]) were associated with higher RSV awareness. There was a high level of acceptance for maternal vaccines (future: 79.3%) and infant immunisation (all: 81.7%).

CONCLUSION

While RSV awareness and immunisation acceptance were high, there was limited knowledge of severity of RSV, especially in future parents. Education campaigns need to be developed to increase RSV knowledge.

Respiratory Syncytial Virus Hospital-Based Burden of Disease in Children Younger Than 5 Years, 2015-2022

Importance

Respiratory syncytial virus (RSV) resurgences have been noted following the COVID-19 pandemic in many countries. Recent findings suggest that the 2021 and 2022 RSV seasons were more severe than in past seasons, and age distribution may have shifted toward older children in the younger than 5 years age group.

Objectives

To estimate age-specific changes in RSV hospital-based burden of disease before and after the COVID-19 pandemic and to compare incidence by Medicaid use.

Design, Setting, and Participants

This retrospective cohort study included children younger than 5 years diagnosed with RSV and bronchiolitis at 50 US children's hospitals in 10 US geographic regions. The included participants had an encounter in intensive care, inpatient, emergency, or observational units, between June 1, 2015, and March 31, 2023.

Exposures

Diagnosis of RSV, bronchiolitis, or both at encounter.

Main Outcome and Measures

Incidence rate ratio of hospital use within each care unit before vs after the COVID-19 pandemic. It was hypothesized a priori that incidence of hospital use would increase overall in 2021 and 2022 compared with 2015 to 2019 and that the increase would be greater among children 12 months and older.

Results

Of 924 061 study participants (median [IQR] age, 8 (5-16) months; 535 619 [58.0%] male), 348 077 (37.7%) were diagnosed with RSV. Of these, 187 850 (54.0%) were hospitalized. Incidence rate ratios of hospitalization increased for all ages in 2021 and 2022 compared with 2015 to 2019. Children aged 24 to 59 months were 4.86 (95% CI, 4.75-4.98) times as likely to be hospitalized in 2022 compared with 2015 to 2019, whereas infants aged 0 to 5 months were 1.77 (95% CI, 1.74-1.80) times as likely. Medicaid patients were more likely to be hospitalized than non-Medicaid patients regardless of year.

Conclusions and Relevance

Hospitalizations for RSV and bronchiolitis demonstrated atypical seasonality in 2021 and 2022, with an overall increase in RSV encounters. Postpandemic RSV hospitalization increased for all ages, but especially among older children, whereas bronchiolitis hospitalization was decreased or unchanged compared with earlier seasons. These findings suggest some of the observed increase in RSV hospital use may be due to increased testing.

Respiratory Syncytial Virus Infections in Recipients of Bone Marrow Transplants: A Systematic Review and Meta-Analysis

Human Respiratory Syncytial Virus (RSV) is a common cause of respiratory tract infections. Usually associated with infants and children, an increasing amount of evidence suggests that RSV can cause substantial morbidity and mortality in immunocompromised individuals, including recipients of bone marrow transplantation (BMT). The present systematic review was therefore designed in accordance with the PRISMA guidelines to collect available evidence about RSV infections in BMT recipients. Three medical databases (PubMed, Embase, and MedRxiv) were therefore searched for eligible observational studies published up to 30 September 2023 and collected cases were pooled in a random-effects model. Heterogeneity was assessed using I2 statistics. Reporting bias was assessed by means of funnel plots and regression analysis. Overall, 30 studies were retrieved, including 20,067 BMT cases and 821 RSV infection episodes. Of them, 351 were lower respiratory tract infections, and a total of 78 RSV-related deaths were collected. A pooled attack rate of 5.40% (95% confidence interval [95%CI] 3.81 to 7.60) was identified, with a corresponding incidence rate of 14.77 cases per 1000 person-years (95%CI 9.43 to 20.11), and a case fatality ratio (CFR) of 7.28% (95%CI 4.94 to 10.60). Attack rates were higher in adults (8.49%, 95%CI 5.16 to 13.67) than in children (4.79%, 95%CI 3.05 to 7.45), with similar CFR (5.99%, 95%CI 2.31 to 14.63 vs. 5.85%, 95%CI 3.35 to 10.02). By assuming RSV attack rates as a reference group, influenza (RR 0.518; 95%CI 0.446 to 0.601), adenovirus (RR 0.679, 95%CI 0.553 to 0.830), and human metapneumovirus (RR 0.536, 95%CI 0.438 to 0.655) were associated with a substantially reduced risk for developing corresponding respiratory infection. Despite the heterogeneous settings and the uneven proportion of adult and pediatric cases, our study has identified high attack rates and a substantial CFR of RSV in recipients of BMT, stressing the importance of specifically tailored preventive strategies and the need for effective treatment options.

An epidemiological investigation of high-risk infants for Respiratory Syncytial Virus infections: a retrospective cohort study

BACKGROUND

Respiratory Syncytial Virus (RSV) infections may lead to severe consequences in infants born preterm with breathing problems (such as bronchopulmonary dysplasia (BPD) and respiratory distress syndrome (RDS)) or congenital heart diseases (CHD). Since studies investigating the influence of different gestational age (WGA) and concomitant specific comorbidities on the burden of RSV infections are scarce, the present study aimed to better characterize these high-risk populations in the Italian context.

METHODS

This retrospective, longitudinal and record-linkage cohort study involved infants born between 2017 and 2019 in Lazio Region (Italy) and is based on data extracted from administrative databases. Each infant was exclusively included in one of the following cohorts: (1) BPD-RDS (WGA ≤35 with or without CHD) or (2) CHD (without BPD and/or RDS) or (3) Preterm (WGA ≤35 without BPD (and/or RDS) or CHD). Each cohort was followed for 12 months from birth. Information related to sociodemographic at birth, and RSV and Undetermined Respiratory Agents (URA) hospitalizations and drug consumption at follow-up were retrieved and described.

RESULTS

A total of 8,196 infants were selected and classified as 1,084 BPD-RDS, 3,286 CHD and 3,826 Preterm. More than 30% of the BPD-RDS cohort was composed by early preterm infants (WGA ≤ 29) in contrast to the Preterm cohort predominantly constitute by moderate preterm infants (98.2%), while CHD infants were primarily born at term (83.9%). At follow-up, despite the cohorts showed similar proportions of RSV hospitalizations, in BPD-RDS cohort hospitalizations were more frequently severe compared to those occurred in the Preterm cohort (p<0.01), in the BPD-RDS cohort was also found the highest proportion of URA hospitalizations (p<0.0001). In addition, BPD-RDS infants, compared to those of the remaining cohorts, received more frequently prophylaxis with palivizumab (p<0.0001) and were more frequently treated with adrenergics inhalants, and glucocorticoids for systemic use.

CONCLUSIONS

The assessment of the study clinical outcomes highlighted that, the demographic and clinical characteristics at birth of the study cohorts influence their level of vulnerability to RSV and URA infections. As such, continuous monitoring of these populations is necessary in order to ensure a timely organization of health care system able to respond to their needs in the future.

Comparison of mortality and outcomes of four respiratory viruses in the intensive care unit: a multicenter retrospective study

This retrospective study aimed to compare the mortality and burden of respiratory syncytial virus (RSV group), SARS-CoV-2 (COVID-19 group), non-H1N1 (Seasonal influenza group) and H1N1 influenza (H1N1 group) in adult patients admitted to intensive care unit (ICU) with respiratory failure. A total of 807 patients were included. Mortality was compared between the four following groups: RSV, COVID-19, seasonal influenza, and H1N1 groups. Patients in the RSV group had significantly more comorbidities than the other patients. At admission, patients in the COVID-19 group were significantly less severe than the others according to the simplified acute physiology score-2 (SAPS-II) and sepsis-related organ failure assessment (SOFA) scores. Using competing risk regression, COVID-19 (sHR = 1.61; 95% CI 1.10; 2.36) and H1N1 (sHR = 1.87; 95% CI 1.20; 2.93) were associated with a statistically significant higher mortality while seasonal influenza was not (sHR = 0.93; 95% CI 0.65; 1.31), when compared to RSV. Despite occurring in more severe patients, RSV and seasonal influenza group appear to be associated with a more favorable outcome than COVID-19 and H1N1 groups.

Engineered dityrosine-bonding of the RSV prefusion F protein imparts stability and potency advantages

Viral fusion proteins facilitate cellular infection by fusing viral and cellular membranes, which involves dramatic transitions from their pre- to postfusion conformations. These proteins are among the most protective viral immunogens, but they are metastable which often makes them intractable as subunit vaccine targets. Adapting a natural enzymatic reaction, we harness the structural rigidity that targeted dityrosine crosslinks impart to covalently stabilize fusion proteins in their native conformations. We show that the prefusion conformation of respiratory syncytial virus fusion protein can be stabilized with two engineered dityrosine crosslinks (DT-preF), markedly improving its stability and shelf-life. Furthermore, it has 11X greater potency as compared with the DS-Cav1 stabilized prefusion F protein in immunogenicity studies and overcomes immunosenescence in mice with simply a high-dose formulation on alum.

Changes in Spectrum of Respiratory Pathogen Infections and Disease Severity Among Children in Hohhot, China: Impact of COVID-19 Prevention Measures

BACKGROUND This retrospective study evaluated the effects of specific COVID-19 preventive measures, including the use of medical masks, nucleic acid testing, and patient isolation, on respiratory infections, disease severity, and seasonal patterns among children in Hohhot, located in northern China. Understanding these alterations is pivotal in developing effective strategies to handle pediatric respiratory infections within the context of continuous public health initiatives. MATERIAL AND METHODS At the First Hospital of Hohhot, throat swabs were collected from 605 children with community-acquired respiratory between January 2022 and March 2023 for pathogen infection spectrum detection using microarray testing. RESULTS Among the patients, 56.03% were male, and their average age was 3.45 years. SARS-CoV-2 infections were highest between October 2022 and January 2023. Influenza A peaked in March 2023, and other pathogens such as respiratory syncytial virus and influenza B virus disappeared after December 2022. The proportion of mixed infections was 41.94% among SARS-CoV-2 patients, while other pathogens had mixed infection rates exceeding 57.14%. Before December 2022, the mean WBC count for Streptococcus pneumoniae and Haemophilus influenzae was 8.83×10⁹/L, CRP was 18.36 mg/L, and PCT was 1.11 ng/ml. After December 2022, these values decreased significantly. Coughing, difficulty breathing, running nose, and lower respiratory tract infection diagnoses decreased in December 2022, except for SARS-CoV-2 infections. CONCLUSIONS SARS-CoV-2 peaked around November 2022, influenza A peaked in March 2023, and other pathogens like respiratory syncytial virus and influenza B virus were greatly reduced after December 2022. Inflammatory markers and respiratory symptoms decreased after December 2022, except for SARS-CoV-2.

Longitudinal associations between serum IL-34 with severity and prognosis in community-acquired pneumonia patients

BACKGROUND

Interleukin-34 (IL-34) is a hematopoietic cytokine and a ligand of colony-stimulating factor 1 receptor (CSF-1R). Numerous studies have demonstrated that IL-34 is involved in several inflammatory diseases. Nevertheless, the role of IL-34 is obscure in community-acquired pneumonia (CAP) patients. This research aimed to assess the associations of serum IL-34 with severity and prognosis in CAP patients through a longitudinal study.

METHODS

CAP patients and healthy volunteers were recruited. Peripheral blood samples were collected. Serum IL-34 and inflammatory cytokines were tested by enzyme linked immunosorbent assay (ELISA). Demographic characteristics and clinical information were acquired through electronic medical records.

RESULTS

Serum IL-34 was elevated in CAP patients compared with healthy volunteers. The content of serum IL-34 was gradually upregulated with increased CAP severity scores. Mixed logistic and linear regression models suggested that serum IL-34 elevation was associated with increased PSI and SMART-COP scores. Correlative analysis found that serum IL-34 was positively correlated with inflammatory cytokines among CAP patients. A longitudinal study indicated that higher serum IL-34 at admission elevated the risks of mechanical ventilation and death during hospitalization. Serum IL-34 had a higher predictive capacity for death than CAP severity scores.

CONCLUSION

There are prominently positive dose-response associations between serum IL-34 at admission with the severity and poor prognosis, suggesting that IL-34 is implicated in the occurrence and development of CAP. Serum IL-34 may serve as a biomarker to forecast disease progression and poor prognosis in CAP patients.

Impact of Subgroup Distribution on Seasonality of Human Respiratory Syncytial Virus: A Global Systematic Analysis

BACKGROUND

Previous studies reported inconsistent findings regarding the association between respiratory syncytial virus (RSV) subgroup distribution and timing of RSV season. We aimed to further understand the association by conducting a global-level systematic analysis.

METHODS

We compiled published data on RSV seasonality through a systematic literature review, and unpublished data shared by international collaborators. Using annual cumulative proportion (ACP) of RSV-positive cases, we defined RSV season onset and offset as ACP reaching 10% and 90%, respectively. Linear regression models accounting for meteorological factors were constructed to analyze the association of proportion of RSV-A with the corresponding RSV season onset and offset.

RESULTS

We included 36 study sites from 20 countries, providing data for 179 study-years in 1995-2019. Globally, RSV subgroup distribution was not significantly associated with RSV season onset or offset globally, except for RSV season offset in the tropics in 1 model, possibly by chance. Models that included RSV subgroup distribution and meteorological factors explained only 2%-4% of the variations in timing of RSV season.

CONCLUSIONS

Year-on-year variations in RSV season onset and offset are not well explained by RSV subgroup distribution or meteorological factors. Factors including population susceptibility, mobility, and viral interference should be examined in future studies.

Clinical Practice Patterns and Risk Factors for Severe Conditions in Pediatric Hospitalizations With Respiratory Syncytial Virus in Japan: A Nationwide Analyses (2018-2022)

BACKGROUND

Respiratory syncytial virus (RSV) represents a global health challenge, especially among younger children. While the disease burden in Japan has been preliminarily quantified, there remains a lack of comprehensive understanding regarding treatment patterns and the influence of known risk factors at a national scale.

MATERIALS AND METHODS

We conducted a retrospective cohort study consisting of 50,482 children under 5 years hospitalized with RSV infections during 2018-2022 using the Medical Data Vision database. We investigated trends in patient characteristics, health resource use, treatment patterns, and laboratory data. Additionally, multivariable modified Poisson regression models were used to investigate the risk factors associated with severe conditions.

RESULTS

We observed an increasing trend in the inpatient healthcare costs and decreasing trends in the use of antibiotics, bronchodilators, systemic corticosteroids and other symptomatic medications from 2018 to 2022. Risk factors associated with severe RSV infections were children less than 1 year (risk ratio, 2.90; 95% CI: 2.53-3.32) and the number of complex chronic diseases (risk ratio for 1 disease, 2.68; 95% CI: 2.34-3.06: risk ratio for 2 or more diseases, 6.91; 95% CI: 5.81-8.21). Annual inpatient healthcare costs for RSV infections were estimated at 11-14 billion Japanese Yen for younger children.

CONCLUSIONS

Our study observed the changes in practice patterns and health resource use for children hospitalized with RSV infections and identified risk factors associated with severe conditions. These findings provide insights for policymakers and clinicians aiming to devise strategies for further improving clinical practices, including newly developed vaccines and single-dose long-acting monoclonal antibodies.

Inhaled "Muco-Trapping" Monoclonal Antibody Effectively Treats Established Respiratory Syncytial Virus (RSV) Infections

Respiratory syncytial virus (RSV) causes substantial morbidity and mortality in infants, the immunocompromised, and the elderly. RSV infects the airway epithelium via the apical membrane and almost exclusively sheds progeny virions back into the airway mucus (AM), making RSV difficult to target by systemically administered therapies. An inhalable "muco-trapping" variant of motavizumab (Mota-MT), a potent neutralizing mAb against RSV F is engineered. Mota-MT traps RSV in AM via polyvalent Fc-mucin bonds, reducing the fraction of fast-moving RSV particles in both fresh pediatric and adult AM by ≈20-30-fold in a Fc-glycan dependent manner, and facilitates clearance from the airways of mice within minutes. Intranasal dosing of Mota-MT eliminated viral load in cotton rats within 2 days. Daily nebulized delivery of Mota-MT to RSV-infected neonatal lambs, beginning 3 days after infection when viral load is at its maximum, led to a 10 000-fold and 100 000-fold reduction in viral load in bronchoalveolar lavage and lung tissues relative to placebo control, respectively. Mota-MT-treated lambs exhibited reduced bronchiolitis, neutrophil infiltration, and airway remodeling than lambs receiving placebo or intramuscular palivizumab. The findings underscore inhaled delivery of muco-trapping mAbs as a promising strategy for the treatment of RSV and other acute respiratory infections.

Underreporting and Misclassification of Respiratory Syncytial Virus-Coded Hospitalization Among Adults in Denmark Between 2015-2016 and 2017-2018

BACKGROUND

Low awareness and lack of routine testing for respiratory syncytial virus (RSV) infections among adults has led to underreporting in hospital records. This study aimed to assess the underreporting and misclassification of RSV infections among adults hospitalized with an respiratory tract infection (RTI)-coded hospitalization.

METHODS

This study is an observational cohort study of RSV-associated hospitalizations among Danish adults (≥18 years old) conducted, between 2015 to 2018. Data were extracted from the Danish National Patient Registry (DNPR) and the Danish Microbiology Database. We identified RSV-positive hospitalizations by linking RTI-coded hospitalizations with a positive RSV test.

RESULTS

Using hospital admission registries, we identified 440 RSV-coded hospitalizations, of whom 420 (95%) had a positive RSV test registered. By linking patients with RTI-coded hospital admissions to RSV test result, we found 570 additional episodes of RSV-positive hospitalizations without an RSV-coded diagnosis.

CONCLUSIONS

Our study of national register data showed that RSV is underreported among Danish adults. The study showed that the reliability of hospitalization data to estimate the burden of RSV among adults is questionable and are sensitive to changes in practice over time, even with complete nationwide healthcare data. Healthcare data can be useful to observe seasonality but to estimate the disease burden, prospective surveillance is recommended.

Unmasking the potential of secretory IgA and its pivotal role in protection from respiratory viruses

Mucosal immunity has regained its spotlight amidst the ongoing Coronavirus disease 19 (COVID-19) pandemic, with numerous studies highlighting the crucial role of mucosal secretory IgA (SIgA) in protection against Severe acute respiratory syndrome coronavirus-2 or SARS-CoV-2 infections. The observed limitations in the efficacy of currently authorized COVID-19 vaccines in inducing effective mucosal immune responses remind us of the limitations of systemic vaccination in promoting protective mucosal immunity. This resurgence of interest has motivated the development of vaccine platforms capable of enhancing mucosal responses, specifically the SIgA response, and the development of IgA-based therapeutics. Recognizing viral respiratory infections as a global threat, we would like to comprehensively review the existing knowledge on mucosal immunity, with a particular emphasis on SIgA, in the context of SARS-CoV-2, influenza, and Respiratory Syncytial Virus (RSV) infections. This review aims to describe the structural and functional specificities of SIgA, along with its nuanced role in combating influenza, RSV, and SARS-CoV-2 infections. Subsequent sections further elaborate promising vaccine strategies, including mucosal vaccines against Influenza, RSV, and SARS-CoV-2 respiratory viruses, currently undergoing preclinical and clinical development. Additionally, we address the challenges associated with mucosal vaccine development, concluding with a discussion on IgA-based therapeutics as a promising platform for the treatment of viral respiratory infections. This comprehensive review not only synthesizes current insights into mucosal immunity but also identifies critical knowledge gaps, strengthening the way for further advancements in our current understanding and approaches to combat respiratory viral threats.

Characterisation of RSV infections in children without chronic diseases aged 0-36 months during the post-COVID-19 winter season 2022/2023

Background

Respiratory syncytial virus (RSV) is one of the leading causes of hospitalisation, morbidity, and mortality due to respiratory infection in the first years of life. This longitudinal prospective study outlines the 2022/23 season's viral patterns in Austria after the epidemiological changes determined by public health measures. We aimed to highlight differences within the RSV subtypes and genotypes in 0-36-month-old children without chronic diseases in the outpatient setting.

Methods

From November 2022 to March 2023 children younger than 36 months admitted to Vienna's largest paediatric primary healthcare centre with an acute respiratory infection were enrolled in this study. Nasal swabs and multiplex PCR panels detected 20 viruses including RSV subtypes and genotypes. Clinical presentation, features, and treatment of the participants were documented and analysed using the Modified Tal Score (MTS). Patients were scheduled for a telemedical follow-up one week after the initial appointment. Analysis was done using descriptive statistics, including Cramér V and binominal logarithmic regression.

Results

Among the 345 samples from 329 children, RSV was the most common virus (31.9%), followed by influenza (17.5%) and rhinovirus infections (20.58%). Of the RSV positive samples, only 13 cases were RSV subtype A (11.8%), whereas 97 were of subtype B (87.3%); ON1 and BA9 were the only detectable RSV genotypes (ON1: BA9 = 1:9.25). RSV was the main predictor of hospitalisation (OR: 7.5, 95% CI: (1.46-38.40), and age had a significant but smaller effect (OR: 0.89, 95% CI: (0.81-0.99). Almost all patients' clinical status improved within the first days.

Conclusion

RSV cases showed a rapid onset in late November 2022, and subtype B was predominant throughout the season. RSV infection was associated with higher hospitalisation rates, even after excluding high-risk patients (preterm and severe chronic diseases population).Further testing in the upcoming winter seasons will improve our knowledge of the dominant subtype and its association with disease severity, especially with the development of novel RSV vaccine candidates.

Respiratory syncytial virus infection in adults: Differences with influenza

INTRODUCTION

Respiratory syncytial virus (RSV) causes an acute respiratory illness similar to influenza, although there are few data comparing both of them in adults. The existence of clinical differences between these two infections could have implications for their management.

MATERIALS AND METHODS

Retrospective observational cohort study including 63 adults with positive PCR for RSV and 221 for influenza during winter 2018-2019. Epidemiological, clinical characteristics and outcomes were contrasted between both groups.

RESULTS

Compared to influenza, RSV-positive patients presented a higher association with active neoplasia (OR=2.9; 95% CI: 1.2-6.9), dependence for basic activities of daily living (OR=3.4; 95% CI: 1.4-8.2) and immunosuppression due to chronic glucocorticoid administration (OR=7.6; 95% CI: 1.6-36.1). At diagnosis, fever was less common (OR=0.3; 95% CI: 0.2-0.7), and C-reactive protein level ≥100mg/l was more frequent (OR=2.1; 95% CI: 1.0-4.5). They developed bacterial co-infection by Staphylococcus aureus in a higher proportion (OR=8.3; 95% CI: 1.5-46.9) and presented a greater need for admission to the intensive care unit (OR=5.4; 95% CI: 1.4-19.2).

CONCLUSION

RSV is an important cause of respiratory illness in adults during the influenza season. It especially affects vulnerable patients with chronic underlying diseases, and has a higher morbidity than influenza. For all these reasons, specific detection, prevention and treatment of RSV is necessary in order to reduce the consumption of health care resources due to RSV disease in adults.

Measurement of the interbronchial angle in acute viral bronchiolitis

BACKGROUND

Acute viral bronchiolitis (AVB) is the most common lower airway infection in children under 2 years. Attempts to determine disease severity based on clinical and radiological manifestations are a major challenge. Measurements of the anatomy of the trachea and main bronchi are not only limited to pure anthropometry, but are also useful for better care of critically ill patients. The purpose of the study is to verify the association between measurements of the interbronchial angle (ITB) and the severity of respiratory disease.

METHODS

A cross-sectional study, which included all patients admitted to the Santo Antônio Children's Hospital, over a period of 1 year, with diagnosis of AVB by respiratory syncytial virus (RSV) was designed. ITB angle was measured and clinical characteristics were analyzed. Quantitative variables were compared and correlation analysis was performed using Pearson's correlation coefficient. A receiving operator characteristic (ROC) curve was performed. P-value <0.05 was statistically significant.

RESULTS

A total of 425 patients with AVB due to RSV were included. Most of these patients were male and the median age was 130 days, 91.11% of them required oxygen therapy through a nasal catheter, 3.3% used noninvasive ventilation and 4% used mechanical ventilation. Those who required MV or NIV and intensive care unit support were considered severe. The mean ITB was lower for these patients than for those of lesser severity (p < 0.05).

CONCLUSION

The present study demonstrates that there is an association between ITB and AVB severity. The smaller the ITB, the greater the disease severity.

A Retrospective Public Health Assessment and Management in Terms of the Social and Clinical Risk Factors of Respiratory Syncytial Virus Infection in Northern Canada

Background The predominant source of respiratory infections in Northern Canada stems from RSV, leading to potentially life-threatening lower respiratory tract infections in children below the age of 2. Typically, RSV begins to appear in November or December and persists until April or May. Synagis® (Palivizumab), a monoclonal antibody, is employed to mitigate or reduce the effects of RSV. Past research indicated a reduction in hospitalizations with the use of Synagis®. Aim The aim is to estimate the cost-benefit analysis by comparing the health services cost with Synagis® program cost. Also evaluate the association of identified risk factors with the severity of RSV infection. Material and methods The dependent variable is categorized as: "Mild-Medium" cases that didn't undergo intubation or require medical evacuation; "Severe" cases that underwent intubation, required medical evacuation, and intensive care unit facilities. We also calculate the cost of health services and Synagis® of each year. Results It has been found that babies who exclusively breastfed and regularly took vitamin D did not develop severe forms of infection. Prenatal smoking and shared and crowded accommodations contribute to the spreading of RSV. The average cost of health services per participant was higher than that of the Synagis program. Conclusion They are promoting the Synagis® program during the season. Standardize the regulations prohibiting smoking around small children since they are more vulnerable to infection. Practice breastfeeding up to 24-month-old babies.

Impact of Respiratory Bacterial Codetection on Outcomes in Ventilated Infants With Bronchiolitis

BACKGROUND

Viral bronchiolitis is a common cause of acute respiratory failure requiring intubation for infants. Bacterial respiratory tract infections can occur with bronchiolitis, although their prevalence and impact on outcomes are unclear, especially with increased use of noninvasive respiratory support.

METHODS

This was a single-center retrospective cohort study of children <2 years old requiring intubation in the emergency department for bronchiolitis from 2012 to 2017 who had viral testing plus a lower respiratory culture obtained. We evaluated the impact of bacterial codetection (positive respiratory culture plus moderate or many polymorphonuclear neutrophils on Gram stain) on mechanical ventilation (MV) duration and intensive care unit length of stay using multivariable gamma regression.

RESULTS

Of 149 patients enrolled, 52% had bacterial codetection. In adjusted analysis, patients with codetection had shorter MV duration [adjusted relative risk (aRR) 0.819, 95% confidence interval (CI): 0.69-0.98; marginal mean duration of 5.31 days (4.71-5.99) compared to 6.48 days (5.72-7.35) without codetection]. Patients with codetection had a shorter intensive care unit stay [aRR 0.806 (0.69-0.94); marginal mean length of stay 6.9 days (6.21-7.68) vs. 8.57 days (7.68-9.56) without codetection]. The association between codetection and duration of ventilation appears confined to those receiving earlier antibiotics (less than the median time) rather than later antibiotics [aRR 0.738 (0.56-0.95) for earlier vs. aRR 0.92 (0.70-1.18) for later].

CONCLUSIONS

Respiratory bacterial codetection is common and associated with shorter MV duration in infants requiring early intubation for bronchiolitis. Early antibiotics may contribute to these outcomes, but further multicenter studies are needed to understand the role of codetection and antibiotics on bronchiolitis outcomes.

Respiratory syncytial virus immunoprophylaxis: Novel opportunities and a call for equity

With the approval of the first vaccines against respiratory syncytial virus (RSV) and a novel RSV-neutralizing antibody, 2023 has been perceived as a game-changing year in preventing severe outcomes of RSV infections in infants and the elderly. However, the costs of these pharmaceuticals are high, while RSV disproportionately impacts populations of low-to-middle-income regions, which may continue to suffer from a lack of pharmaceutical measures for RSV prevention under health and socioeconomic disparities. This paper presents an overview of the characteristics, clinical results, and approval status of various RSV vaccines and anti-RSV antibodies. It posits that wealthy nations cannot monopolize RSV immunoprophylaxis and should work jointly to make it available to lower-income countries. An approach toward RSV immunoprophylaxis equity based on five points is offered: (1) integration of RSV vaccines and antibodies into the existing global humanitarian distribution systems, (2) using affordable RSV vaccine pricing models, (3) enforcing equity as a part of national and global public health strategy, (4) implementing equitable allocation frameworks for RSV immunoprophylaxis, and (5) promoting local manufacturing. Such a plan needs to be put into action as soon as possible to avoid delays in serving the populations with the highest needs related to RSV burden.

A molecular perspective for the development of antibodies against the human respiratory syncytial virus

The human respiratory syncytial virus (hRSV) is the leading etiologic agent causing respiratory infections in infants, children, older adults, and patients with comorbidities. Sixty-seven years have passed since the discovery of hRSV, and only a few successful mitigation or treatment tools have been developed against this virus. One of these is immunotherapy with monoclonal antibodies against structural proteins of the virus, such as Palivizumab, the first prophylactic approach approved by the Food and Drug Administration (FDA) of the USA. In this article, we discuss different strategies for the prevention and treatment of hRSV infection, focusing on the molecular mechanisms against each target that underly the rational design of antibodies against hRSV. At the same time, we describe the latest results regarding currently approved therapies against hRSV and the challenges associated with developing new candidates.