The Impact of RSV-Associated Respiratory Disease on Children in Asia

Clinical, Meteorological, and Air Quality Factors Associated with Ambulatory Pediatric Respiratory Syncytial Virus Infection in Machala, Ecuador, 2018-2023

Implementation of RSV prevention strategies requires an understanding of seasonal virus epidemiology; yet, such data are lacking in many tropical regions. We describe the seasonality and environmental factors associated with RSV activity in Machala, Ecuador. From July 2018 to July 2023, we analyzed nasopharyngeal samples from children younger than 5 years with an acute respiratory illness using Biofire FilmArray v.1.7™. Meteorological data were obtained from Ecuador's Instituto Nacional de Meteorología e Hidrología. RSV detection was associated with mean outdoor air temperature (threshold 27 °C, area under the curve (AUC) 0.74, p < 0.001) that was even stronger when using a 4-week lag (threshold 27 °C, AUC 0.865, p < 0.001) and with precipitation greater than 0.5 mm/week using a 6-week lag (p = 0.008). This finding could provide guidance for the ideal timing to improve RSV surveillance and implement RSV prevention measures in Machala, including universal administration of extended half-life monoclonal antibody to infants entering their first RSV season.

Multiple merger coalescent inference of effective population size

Variation in a sample of molecular sequence data informs about the past evolutionary history of the sample's population. Traditionally, Bayesian modelling coupled with the standard coalescent is used to infer the sample's bifurcating genealogy and demographic and evolutionary parameters such as effective population size and mutation rates. However, there are many situations where binary coalescent models do not accurately reflect the true underlying ancestral processes. Here, we propose a Bayesian non-parametric method for inferring effective population size trajectories from a multifurcating genealogy under the [Formula: see text]-coalescent. In particular, we jointly estimate the effective population size and the model parameter for the Beta-coalescent model, a special type of [Formula: see text]-coalescent. Finally, we test our methods on simulations and apply them to study various viral dynamics as well as Japanese sardine population size changes over time. The code and vignettes can be found in the phylodyn package.This article is part of the theme issue '"A mathematical theory of evolution": phylogenetic models dating back 100 years'.

Trends in Proportions of Respiratory Syncytial Virus Infections Among Reported Respiratory Tract Infection Cases in Children Aged 0 to 5 Years in Western Pacific and Southeast Asia Regions: A Systematic Review and Meta-Analysis

BACKGROUND

Respiratory syncytial virus (RSV) is an important cause of bronchiolitis and pneumonia in children globally. This study aimed to incorporate new data to update estimates of RSV burden in children through 5 years of age in Western Pacific and Southeast Asia Regions.

METHODS

A systematic review and meta-analysis were conducted to examine the proportion of RSV among cases of respiratory tract infection (RTI) in children in Western Pacific and Southeast Asia Regions using random effects models. Studies were eligible if they met the following inclusion criteria: (1) observational studies such as cohort and cross-sectional studies; (2) studies on humans; (3) studies on patients with RTI or influenza-like illness (ILI); (4) studies reporting incidence or proportion of RSV infection among respiratory related illness; and (5) studies on children aged 5 years or less.

FINDINGS

A total of 4403 studies were identified from an initial search. After screening titles, abstracts, and full-text review, a total of 173 studies that met predefined eligibility criteria were included in the analysis. The overall proportion of RSV infections among all ARTIs was 18.7% (95% CI: 16.0%-21.5%), whereas the proportion of RSV infections among LRTIs was 28.7% (95% CI: 2.6%-30.3%) in children in Western Pacific and Southeast Asia Regions between 1970 and 2020. The proportion of RSV infections peaked in the 1980s at 33.4% (95% CI: 19.8%-48.5%), having increased from 10.6% (95% CI: 2.9%-22.2%) in the 1970s. It then showed a decreasing trend, with 28.9% (95% CI: 18.8%-40.3%) in the 1990s, 24.5% (95% CI: 22.3%-26.8%) in the 2000s, and 20.1% (95% CI: 17.8%-22.5%) in the 2010s. By country, Myanmar (50.0%; 95% CI, 47.5%-52.4%) and New Zealand (45.3%; 95% CI, 37.1%-53.7%) had the highest proportion during the overall time period, followed by Bhutan (45.2%; 95% CI, 36.4%-54.3%), Lao PDR (41.0%; 95% CI, 36.2%-46.0%), and Vietnam (35.5%; 95% CI, 19.3%-53.6%).

INTERPRETATION

Substantial RSV-associated disease burden occurs in children in Western Pacific and Southeast Asia Regions. Our findings provide new and important evidence of the need for RSV prevention in Western Pacific and Southeast Asia countries. They could inform future preventive policy.

The recent landscape of RSV vaccine research

Respiratory syncytial virus (RSV) causes a significant burden of acute respiratory illness across all ages, particularly for infants and older adults. Infants, especially those born prematurely or with underlying health conditions, face a high risk of severe RSV-related lower respiratory tract infections (LRTIs). Globally, RSV contributes to millions of LRTI cases annually, with a disproportionate burden in low- and middle-income countries (LMICs). The RSV virion outer capsule contains glycoproteins G and F which are essential for viral entry into respiratory epithelial cells and represent key targets for therapeutics development. The F-glycoprotein has several highly conserved antigenic sites that have proven useful targets for the development of monoclonal antibodies (mAbs) against RSV. Historically, prevention in infants was limited to the mAb palivizumab, which, despite its efficacy, was costly and inaccessible in many regions. Recent advancements include nirsevimab, a long-acting mAb that has shown substantial efficacy in reducing medically attended RSV-related disease in infants, in phase III clinical trials, early regional and national real-world data. In addition, three new vaccines have been approved: two protein subunit vaccines and a messenger RNA vaccine. The vaccines are all licenced for use in older adults, with one also approved as a maternal vaccine. Promising candidates in development include the mAb clesrovimab, which has an extended half-life and high levels in the nasal epithelial lining and high safety and efficacy profiles in late-stage trials. There are also a wide range of vaccine candidates currently in late-stage clinical trials. These developments signify a major advancement in RSV prevention strategies, offering improved protection for high-risk populations. With the ongoing rollout of the recently licenced vaccines and mAbs internationally, the landscape of RSV care is rapidly changing. We also must ensure these advances reach those in LMICs who need these therapies most.

Infection of nonclassic monocytes by respiratory syncytial virus induces an imbalance in the CD4+ T-cell subset response

Respiratory syncytial virus (RSV) causes lower respiratory tract infections in infants and young children, leading to a pathogenesis-associated imbalance in CD4+ T-cell subsets and monocyte subsets. To investigate whether RSV affects the imbalance of CD4+ T-cells through monocytes, we examined the effects of the RSV-infected monocyte subset on CD4+ T-cell subsets, namely, Th1, Th2, Th17, and regulatory T (Treg) subsets, on proliferation in vitro and identified key monocyte-derived cytokines. We found that RSV efficiently infects CD16+ monocytes, but not CD16- monocytes, via cocultures of CD4+ T-cells with RSV-infected CD16+ monocytes, inhibits Treg cell proliferation and increases Th2 cell frequency, suggesting that RSV causes an imbalance in the CD4+ T-cell subset by primarily infecting CD16+ monocytes. Our data also revealed that IL-1β and IL-10 are key cytokines responsible for the activities of RSV-infected CD16+ monocytes. In a mouse model, we found that high-efficiency RSV infection of mouse Ly6C- monocytes, corresponding to CD16+ monocytes in humans, and adoptive transfer of Ly6C- monocytes during RSV infection decreased the Treg frequency in the lungs and aggravated pneumonia. Our data indicate that RSV can increase its pathogenesis through infection of nonclassic monocytes, leading to a CD4+ T-cell imbalance.IMPORTANCEThis study identified a pathogenesis pathway related to the RSV-nonclassic monocyte-IL-1β/IL-10-CD4+ T-cell subset balance, which links the heterogeneity of monocytes to RSV pathogenesis and elucidates a new mechanism by which RSV infection disrupts the balance of CD4+ T cells during RSV infection. These new findings provide potential therapeutic targets for RSV infection.

Prevalence and Genetic Diversity of Respiratory Syncytial Virus Reinfections in Young Thai Children, 2016-2023

Although a vaccine for respiratory syncytial virus (RSV) is now available for pregnant women and the elderly, RSV remains a significant cause of respiratory illness in children globally. Reinfections by the same or different RSV subgroups in children residing in the tropics are currently under-studied. Therefore, we examined the patterns of RSV infection and reinfection in Thai children aged ≤ 5 years with respiratory symptoms from 2016 to 2023. Screening of 7710 pediatric respiratory specimens identified 1245 RSV-positive samples (16.1%), mostly from the rainy months (July-November). Interestingly, 74 children experienced two infections, and 6 had three infections. Reinfection by different RSV subgroups occurred in 30 children: 21 were initially infected with RSV-B and later with RSV-A, while 9 had the reverse pattern. Reinfections only by either RSV-A or RSV-B were observed in 22 and 2 children, respectively, with one child infected with RSV-A three times. All RSV-A reinfections belonged to the ON1 genotype, while RSV-B reinfections were BA9. Notably, reinfections across different seasons were observed within homologous pairs. These findings suggest a transitory immunity to natural RSV infection and provide the knowledge that may help optimize pediatric vaccination schedule. Ongoing epidemiological data on RSV are essential in monitoring genotype circulation and vaccine effectiveness.

Key Challenges to Understanding the Burden of Respiratory Syncytial Virus in Older Adults in Southeast Asia, the Middle East, and North Africa: An Expert Perspective

INTRODUCTION

Respiratory syncytial virus (RSV) is a common, highly contagious pathogen and a leading cause of serious illness among infants and older adults. While existing scientific evidence has predominantly focused on the epidemiology and disease burden of RSV in infants, data in older adults remain limited in some countries, including those in Southeast Asia (SEA) and the Middle East and North Africa (MENA) region. Here, we outline the key challenges for understanding the burden of RSV in older adults in SEA and the MENA region and we propose opportunities for improving understanding and eventually reducing the impact of RSV.

MAIN FINDINGS AND CONCLUSIONS

A key challenge identified by the expert group, particularly in older adults, is a lack of awareness (among healthcare professionals, policy makers, and the public) of RSV burden and the associated risks for severe outcomes. This is often confounded by the complexities of underdiagnosis, surveillance limitations, and comorbidities. To address these issues, we suggest medical education initiatives for physicians in SEA and the MENA region to better understand the need to protect older adults from RSV, and encourage more widespread routine testing to better understand the burden of RSV. We also recommend surveillance studies in these regions to provide comprehensive and accurate epidemiological data on RSV in older adults. Finally, in the absence of current surveillance data in these regions, we propose extrapolating existing global data and local pediatric data to inform the likely burden of RSV in older adults. A graphical abstract is available with this article.

Respiratory syncytial virus-associated pneumonia in primary care in Malawi

OBJECTIVE

To identify the prevalence of respiratory syncytial virus (RSV) in a cohort of children under 5 years of age with World Health Organization (WHO)-defined pneumonia and the factors associated with developing severe RSV-associated community-acquired pneumonia (CAP) in primary care in a single centre in Northern Malawi.

METHODS

The BIOmarkers TO diagnose PnEumonia (BIOTOPE) study was a prospective cohort study conducted from March to June 2016 that took place in a primary care centre in Northern Malawi. Data from this study was used to identify the characteristics of children under 5 years of age who presented with RSV and WHO-defined CAP. Means, standard deviations, medians and ranges were calculated for continuous variables. A univariate logistic regression was performed to examine the potential predictor variables.

RESULTS

Four hundred and ninety-four infants presented with CAP and were eligible for inclusion in the study; RSV infection was detected in 205 (41.6%) of the infants. Eight factors were associated with increased risk for RSV CAP in the univariate model: age, born at term, presenting for care in June, crowded living environment, not being exclusively breastfed, not having received zinc or vitamin A supplementation in the last six months. Infants with RSV were more likely to have an oxygen saturation ≤92% compared to infants with other causes of pneumonia and more likely to have severe pneumonia as defined by the WHO.

CONCLUSION

This study supports that RSV-associated CAP is linked to modifiable and non-modifiable risk factors; further research is indicated to determine which interventions would be most impactful. Developing and implementing an infant or maternal vaccine could be a cost-effective way to prevent RSV-associated CAP and mortality in developing nations. More research is needed to understand seasonal patterns of CAP and research over extended periods can offer valuable insights on host, environmental and pathogen-specific factors that contribute to RSV-associated CAP.

Prevalence of respiratory syncytial virus infection and associated factors in children aged under five years with severe acute respiratory illness and influenza-like illness in Ethiopia

OBJECTIVES

Acute respiratory infections because of respiratory syncytial viruses (RSVs) are among the major leading causes of morbidity and mortality in children worldwide. RSV prevalence and its contributing factors among children aged under 5 years in Ethiopia are not well studied. To assess the prevalence and associated factors of RSV infection in children aged under 5 years using influenza sentinel surveillance sites in Ethiopia.

METHODS

A cross-sectional study design was used utilizing influenza-like illness/sever acute respiratory illness surveillance data from January 2021 to December 2022 at the Ethiopian Public Health Institute.

RESULTS

In total, 2234 cases were included, with an overall RSV positivity rate of 16.2%. The RSV positivity rate was high in children aged under 1 year (22.8%) and during fall season (24.8%). The RSV positivity rate was significantly associated with ages under 1 year (adjusted odds ratio [AOR] 2.8, 95% confidence interval [CI]: 1.89-4.15) and 1-2 years (AOR 1.9, 95% CI: 1.26-2.73) and the fall season (AOR 1.67, 95% CI: 1.17-2.38).

CONCLUSION

The study revealed that a considerably high RSV positivity rate was detected in children aged under 5 years. The age of children and season have a significant association with RSV positivity rate. Further studies of RSV viral genotype, clinical characteristics, and disease outcome need to be conducted for a better understanding of the virus and disease outcome.

Respiratory syncytial virus among hospitalized patients of severe acute respiratory infection in Bhutan: Cross-sectional study

Introduction

Respiratory syncytial virus (RSV) is a leading cause of lower respiratory tract infections worldwide, particularly in young children. In Bhutan, respiratory disease continues to be among the top 10 diseases of morbidity for several years. This study aimed to estimate the prevalence of RSV among hospitalized patients with severe acute respiratory infection (SARI) in Bhutan.

Method

Respiratory specimens were collected from SARI patients of all ages in 2016 and 2018 following influenza surveillance guidelines. Specimens were tested for influenza and RSV, human metapneumovirus, adenovirus, and human parainfluenza virus types 1, 2, and 3 using real-time reverse-transcription polymerase chain reaction assay. Descriptive statistics were used to analyze the result in STATA 16.1.

Result

Of the 1339 SARI specimens tested, 34.8% were positive for at least one viral pathogen. RSV was detected in 18.5% of SARI cases, followed by influenza in 13.4% and other respiratory viruses in 3%. The median age of SARI cases was 3 (IQR: 0.8-21 years) years. RSV detection was higher among children aged 0-6 (Adj OR: 3.03; 95% CI: 1.7-5.39) and 7-23 months (Adj OR: 3.01; 95% CI: 1.77-5.12) compared with the children aged 5-15 years. RSV was also associated with breathing difficulty (Adj OR: 1.73; 95% CI: 1.17-2.56) and pre-existing lung disease, including asthma (Adj OR: 2.78; 95% CI: 0.99-7.8).

Conclusion

Respiratory viruses were detected in a substantial proportion of SARI hospitalizations in Bhutan.

Bronchiolitis

Viral bronchiolitis is the most common cause of admission to hospital for infants in high-income countries. Respiratory syncytial virus accounts for 60-80% of bronchiolitis presentations. Bronchiolitis is diagnosed clinically without the need for viral testing. Management recommendations, based predominantly on high-quality evidence, advise clinicians to support hydration and oxygenation only. Evidence suggests no benefit with use of glucocorticoids or bronchodilators, with further evidence required to support use of hypertonic saline in bronchiolitis. Evidence is scarce in the intensive care unit. Evidence suggests use of high-flow therapy in bronchiolitis is limited to rescue therapy after failure of standard subnasal oxygen only in infants who are hypoxic and does not decrease rates of intensive care unit admission or intubation. Despite systematic reviews and international clinical practice guidelines promoting supportive rather than interventional therapy, universal de-implementation of interventional care in bronchiolitis has not occurred and remains a major challenge.

Maternal immunization: trends in South and Southeast Asian countries

Maternal immunization has the potential to reduce neonatal deaths caused by vaccine-preventable infectious diseases. Elimination of maternal and neonatal tetanus from many countries illustrates the potential benefits of maternal immunization as a strategy to decrease neonatal mortality caused by vaccine-preventable infections. Many countries in South and Southeast Asia have high cases of neonatal deaths, which were historically attributed to vaccine-preventable infections. Still, these countries vary in recommendations regarding immunization of pregnant women. We reviewed the current recommendations for the use of tetanus toxoid, tetanus-diphtheria, or tetanus-diphtheria-acellular pertussis (Tdap) vaccines for immunization of pregnant women. In addition to protection against tetanus and diphtheria, administration of the Tdap vaccine to pregnant women could help protect neonates against pertussis until they can receive the first two vaccine doses of their primary course. Vaccination against seasonal influenza is also recommended in many countries worldwide for pregnant women as influenza can pose health risks for the mother-fetus unit and the infant. Despite the recognized benefit of influenza vaccination for pregnant women, only some South and Southeast Asian countries have implemented its recommendation. The success of maternal tetanus vaccination has kindled the interest in vaccines that can be safely administered during pregnancy. Future availability of vaccines against respiratory syncytial virus and group B streptococcus, for use in pregnant women, could help prevent neonatal infections, especially in regions where diseases are less controlled. Communicating the body of evidence that supports maternal immunization to obstetricians is key for achieving optimal vaccination coverage to ensure protection of neonates. The current review aims to create awareness about the existing and potential benefits of maternal immunization in South and Southeast Asia.

Epidemiology and Seasonality of Childhood Respiratory Syncytial Virus Infections in the Tropics

Infections caused by respiratory syncytial virus (RSV) are a major cause of morbidity and mortality in young children worldwide. Understanding seasonal patterns of region-specific RSV activity is important to guide resource allocation for existing and future treatment and prevention strategies. The decades of excellent RSV surveillance data that are available from the developed countries of the world are incredibly instructive in advancing public health initiatives in those regions. With few exceptions, these developed nations are positioned geographically across temperate regions of the world. RSV surveillance across tropical regions of the world has improved in recent years, but remains spotty, and where available, still lacks the necessary longitudinal data to determine the amount of seasonal variation expected over time. However, existing and emerging data collected across tropical regions of the world do indicate that patterns of infection are often quite different from those so well described in temperate areas. Here, we provide a brief summary regarding what is known about general patterns of RSV disease activity across tropical Asia, Africa and South America, then offer additional country-specific details using examples where multiple reports and/or more robust surveillance data have become available.

Lung pathology due to hRSV infection impairs blood-brain barrier permeability enabling astrocyte infection and a long-lasting inflammation in the CNS

The human respiratory syncytial virus (hRSV) is the most common infectious agent that affects children before two years of age. hRSV outbreaks cause a significant increase in hospitalizations during the winter season associated with bronchiolitis and pneumonia. Recently, neurologic alterations have been associated with hRSV infection in children, which include seizures, central apnea, and encephalopathy. Also, hRSV RNA has been detected in cerebrospinal fluids (CSF) from patients with neurological symptoms after hRSV infection. Additionally, previous studies have shown that hRSV can be detected in the lungs and brains of mice exposed to the virus, yet the potential effects of hRSV infection within the central nervous system (CNS) remain unknown. Here, using a murine model for hRSV infection, we show a significant behavior alteration in these animals, up to two months after the virus exposure, as shown in marble-burying tests. hRSV infection also produced the expression of cytokines within the brain, such as IL-4, IL-10, and CCL2. We found that hRSV infection alters the permeability of the blood-brain barrier (BBB) in mice, allowing the trespassing of macromolecules and leading to increased infiltration of immune cells into the CNS together with an increased expression of pro-inflammatory cytokines in the brain. Finally, we show that hRSV infects murine astrocytes both, in vitro and in vivo. We identified the presence of hRSV in the brain cortex where it colocalizes with vWF, MAP-2, Iba-1, and GFAP, which are considered markers for endothelial cells, neurons, microglia, and astrocyte, respectively. hRSV-infected murine astrocytes displayed increased production of nitric oxide (NO) and TNF-α. Our results suggest that hRSV infection alters the BBB permeability to macromolecules and immune cells and induces CNS inflammation, which can contribute to the behavioral alterations shown by infected mice. A better understanding of the neuropathy caused by hRSV could help to reduce the potential detrimental effects on the CNS in hRSV-infected patients.