Acute bronchiolitis: predisposing factors and characterization of infants at risk

Wheezing on admission: a marker for bronchiolitis severity and asthma development

BACKGROUND

Supervised clustering of bronchiolitis patients, according to their clinical characteristics at hospital admission, helps predict short-term hospital outcomes and the risk of developing childhood respiratory illness. Thus, we evaluated the use of wheezing status for stratifying bronchiolitis patients.

METHODS

A prospective cohort study was conducted involving 668 previously healthy, full-term Chilean infants ( < 2 years old) hospitalized with bronchiolitis. Patients categorized based on their wheezing status at hospital admission were monitored during hospitalization and followed for 4 years after discharge.

RESULTS

Wheezing children presented a more severe illness requiring more oxygen during their hospital stay. Upon discharge, they were more likely to develop preschool wheezing at 12 months and asthma at 4 years of age. Among the non-wheezing, those with RSV had more severe disease. Risk factors exclusively associated with persistent asthma development for the wheezing were clinical bacterial coinfection, parental asthma history, and having had a severe bronchiolitis episode. Risk factors exclusive for non-wheezing were maternal smoking during pregnancy and severe retractions.

CONCLUSION

Bronchiolitis patients can be categorized based on their wheezing status at hospital admission, helping predict short-term clinical outcomes and identify infants at risk of developing severe short- and long-term respiratory illnesses.

IMPACT

Stratifying viral bronchiolitis patients using a simple bedside strategy based on their wheezing status at hospitalization can help improve individual-based clinical decisions during hospitalization and enable early identification of infants with a higher risk of developing severe respiratory illnesses and long-term associated diseases. Viral bronchiolitis patients can be stratified based on their hospitalized wheezing status. Wheezing patients exhibited similar clinical patterns during hospitalization and long-term clinical outcomes upon discharge. Wheezing infants were more likely to develop preschool wheezing and asthma.

Effects of COVID-19 pandemic-associated reduction in respiratory infections on infantile asthma development

Background

It is speculated that the coronavirus disease 2019 (COVID-19) pandemic-associated reduction in the prevalence of respiratory tract infections has influenced the incidence of asthma in young children.

Objectives

We investigated an association between the reduction in viral infections and the reduction in asthma in young children.

Methods

The subjects were infants born in the early stages of the COVID-19 pandemic in Japan, which began in February 2020. A questionnaire survey related to asthma and allergy was conducted at 18 months and 3 years of age. These results were compared to those of age-matched infants during the nonpandemic period.

Results

There were no epidemics of viral infectious diseases until the target child was 18 months old. At 18 months, the incidence of asthma/asthmatic bronchitis diagnosed by physicians in pandemic children was significantly lower than that in nonpandemic children. In 3-year-olds, no marked difference was observed between nonpandemic infants and pandemic children, except for an increase in respiratory syncytial virus infection in pandemic children. In a comparative study of the same children at ages 18 months and 3 years, an increased prevalence of asthma/asthmatic bronchitis was observed in pandemic children. Furthermore, the incidence of asthma after respiratory syncytial virus infection in pandemic infants was significantly lower than that in nonpandemic children.

Conclusion

The COVID-19 pandemic-associated reduction in respiratory tract infections may have reduced the incidence of asthma in early childhood, and respiratory syncytial virus infection after 18 months of age had little effect on the onset of asthma. These results indicate the importance of preventing respiratory tract infections in early infancy.

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.

Association between early viral LRTI and subsequent wheezing development, a meta-analysis and sensitivity analyses for studies comparable for confounding factors

INTRODUCTION

Consideration of confounding factors about the association between Lower Respiratory Tract Infections (LRTI) in childhood and the development of subsequent wheezing has been incompletely described. We determined the association between viral LRTI at ≤ 5 years of age and the development of wheezing in adolescence or adulthood by a meta-analysis and a sensitivity analysis including comparable studies for major confounding factors.

METHODS

We performed searches through Pubmed and Global Index Medicus databases. We selected cohort studies comparing the frequency of subsequent wheezing in children with and without LRTI in childhood regardless of the associated virus. We extracted the publication data, clinical and socio-demographic characteristics of the children, and confounding factors. We analyzed data using random effect model.

RESULTS

The meta-analysis included 18 publications (22 studies) that met the inclusion criteria. These studies showed that viral LRTI in children ≤ 3 years was associated with an increased risk of subsequent development of wheezing (OR = 3.1, 95% CI = 2.4-3.9). The risk of developing subsequent wheezing was conserved when considering studies with comparable groups for socio-demographic and clinical confounders.

CONCLUSIONS

When considering studies with comparable groups for most confounding factors, our results provided strong evidence for the association between neonatal viral LRTI and the subsequent wheezing development. Further studies, particularly from lower-middle income countries, are needed to investigate the role of non-bronchiolitis and non-HRSV LRTI in the association between viral LRTI in childhood and the wheezing development later. In addition, more studies are needed to investigate the causal effect between childhood viral LRTI and the wheezing development later.

TRIAL REGISTRATION

Review registration: PROSPERO, CRD42018116955; https://www.crd.york.ac.uk/prospero/display_record.php?ID=CRD42018116955.

Association of early viral lower respiratory infections and subsequent development of atopy, a systematic review and meta-analysis of cohort studies

INTRODUCTION

Existing evidence on the relationship between childhood lower respiratory tract infections (LRTI) and the subsequent atopy development is controversial. We aimed to investigate an association between viral LRTI at <5 years and the development of atopy at > 2 years.

METHODS

We conducted a search at Embase, Pubmed, Web of Science, and Global Index Medicus. We collected data from the included articles. We estimated the odds ratio and the 95% confidence intervals with a random effect model. We determined factors associated with atopy development after childhood LRTI using univariate and multivariate meta-regression analyses. We recorded this systematic review at PROSPERO with the number CRD42018116955.

RESULTS

We included 24 studies. There was no relationship between viral LRTI at <5 years and skin prick test-diagnosed-atopy (OR = 1.2, [95% CI = 0.7-2.0]), unknown diagnosed-atopy (OR = 0.7, [95% CI = 0.4-1.3]), atopic dermatitis (OR = 1.2, [95% CI = 0.9-1.6]), hyperreactivity to pollen (OR = 0.8, [95% CI = 0.3-2.7]), food (OR = 0.8, [95% CI = 0.3-2.5]), or house dust mite (OR = 1.1, [95% CI = 0.6-2.2]). Although not confirmed in all studies with a symmetric distribution of the 23 confounding factors investigated, the overall analyses showed that there was a relationship between childhood viral LRTI at < 5 years and serum test diagnosed-atopy (OR = 2.0, [95% CI = 1.0-4.1]), allergic rhinoconjunctivitis (OR = 1.7, [95% CI = 1.1-2.9]), hyperreactivity diagnosed by serum tests with food (OR = 5.3, [1.7-16.7]) or inhaled allergens (OR = 4.2, [95% CI = 2.1-8.5]), or furred animals (OR = 0.6, [95% CI = 0.5-0.9]).

CONCLUSION

These results suggest that there is no association between viral LRTI at < 5 years and the majority of categories of atopy studied during this work. These results, however, are not confirmed for the remaining categories of atopy and more particularly those diagnosed by serum tests. There is a real need to develop more accurate atopy diagnostic tools.

The global burden of respiratory infections in indigenous children and adults: A review

This review article focuses on common lower respiratory infections (LRIs) in indigenous populations in both developed and developing countries, where data is available. Indigenous populations across the world share some commonalities including poorer health and socio-economic disadvantage compared with their non-indigenous counterparts. Generally, acute and chronic respiratory infections are more frequent and more severe in both indigenous children and adults, often resulting in substantial consequences including higher rates of bronchiectasis and poorer outcomes for patients with chronic obstructive pulmonary disease (COPD). Risk factors for the development of respiratory infections require recognition and action. These risk factors include but are not limited to socio-economic factors (e.g. education, household crowding and nutrition), environmental factors (e.g. smoke exposure and poor access to health care) and biological factors. Risk mitigation strategies should be delivered in a culturally appropriate manner and targeted to educate both individuals and communities at risk. Improving the morbidity and mortality of respiratory infections in indigenous people requires provision of best practice care and awareness of the scope of the problem by healthcare practitioners, governing bodies and policy makers.

Viral bronchiolitis

Viral bronchiolitis is a common clinical syndrome affecting infants and young children. Concern about its associated morbidity and cost has led to a large body of research that has been summarised in systematic reviews and integrated into clinical practice guidelines in several countries. The evidence and guideline recommendations consistently support a clinical diagnosis with the limited role for diagnostic testing for children presenting with the typical clinical syndrome of viral upper respiratory infection progressing to the lower respiratory tract. Management is largely supportive, focusing on maintaining oxygenation and hydration of the patient. Evidence suggests no benefit from bronchodilator or corticosteroid use in infants with a first episode of bronchiolitis. Evidence for other treatments such as hypertonic saline is evolving but not clearly defined yet. For infants with severe disease, the insufficient available data suggest a role for high-flow nasal cannula and continuous positive airway pressure use in a monitored setting to prevent respiratory failure.

Cohort Study of Severe Bronchiolitis during Infancy and Risk of Asthma by Age 5 Years

BACKGROUND

Severe bronchiolitis (ie, bronchiolitis requiring hospital admission) is thought to markedly increase asthma risk, with 30%-50% developing asthma by age 5 years. To date, studies of this association are small, and most are from outside the United States.

OBJECTIVE

The objective of this study was to investigate the association between severe bronchiolitis and risk of asthma in a US birth cohort.

METHODS

We studied a cohort nested within the Massachusetts General Hospital Obstetric Maternal Study (MOMS), a prospective cohort of pregnant women enrolled during 1998-2006. Children of mothers enrolled in MOMS were included in the analysis if they received care within our health system (n = 3653). Diagnoses and medications were extracted from the children's electronic health records; we also examined pregnancy and perinatal risk factors collected for the underlying pregnancy study.

RESULTS

The birth cohort was 52% male, 49% white, and 105 infants (2.9%) had severe bronchiolitis. Overall, 421 children (11.5%) developed asthma by age 5 years. Among the children with severe bronchiolitis, 27.6% developed asthma by age 5 years. In multivariable logistic regression adjusting for 12 risk factors, severe bronchiolitis remained a strong risk factor for developing asthma by age 5 years (odds ratio 2.57; 95% confidence interval 1.61-4.09).

CONCLUSIONS

In a large Boston birth cohort, the frequency of severe bronchiolitis and childhood asthma was similar to published data. Among children with severe bronchiolitis, the risk of developing asthma was lower than prior studies but still high (27.6%). This difference may be due to different study designs, populations, and outcome definitions studied.

Recurrent wheezing 36 months after bronchiolitis is associated with rhinovirus infections and blood eosinophilia

AIM

Links between respiratory syncytial virus bronchiolitis and asthma are well known, but few studies have dealt with wheezing following bronchiolitis induced by other viruses. We assessed the risk factors for recurrent wheezing in infants hospitalised for acute viral bronchiolitis.

METHODS

We followed 313 infants for three years after they were hospitalised for bronchiolitis, caused by 14 different viruses, to identify risk factors for recurrent wheezing. Parents provided feedback on wheezing episodes during telephone interviews 12 (n = 266), 24 (n = 242) and 36 (n = 230) months after hospitalisation.

RESULTS

The frequency of wheezing episodes diminished during the follow-up period: 137 children (51.7%) at 12 months, 117 (48.3%) at 24 months and 93 (40.4%) at 36 months. The risk of wheeze after three years was OR = 7.2 (95% CI 3.9-13.3) if they had episodes of wheezing during the first year after bronchiolitis, 16.8 (8.7-32.7) if they had episodes of wheezing during the second year and 55.0 (22.7-133.2) if they wheezed during both years. Blood eosinophils >400 cells/μL (OR 7.7; CI 1.4-41.8) and rhinovirus infections (3.1; 1.0-9.4) were the major risk factors for recurrent wheezing.

CONCLUSION

Recurrent wheezing 36 months after infant bronchiolitis was associated with rhinoviruses and blood eosinophilia.

Association between respiratory syncytial virus hospitalizations in infants and respiratory sequelae: systematic review and meta-analysis

BACKGROUND

The association between hospitalization for respiratory syncytial virus (RSV) infection in infancy and asthma/wheezing in later life has long been studied. However, no published studies have combined systematic review and meta-analysis of existing evidence.

PURPOSE

To quantify the link between RSV hospitalization in early life and subsequent diagnosis of asthma.

METHOD

A systematic search was conducted using MEDLINE and EMBASE databases. Studies were selected for meta-analysis if they assessed the association between RSV-confirmed hospitalization for up to 3 years of age and asthma/wheezing later in life. Potential sources of heterogeneity were identified by stratified analysis.

RESULTS

Twenty articles representing 15 unique studies of 82,008 unique individuals (including 1533 with RSV-confirmed hospitalization) were selected for meta-analysis. Children who had RSV disease in early life had a higher incidence of asthma/wheezing in later life (odds ratio: 3.84; 95% confidence interval: 3.23-4.58). There was moderate heterogeneity between studies (I² = 45%). The association was found to decrease with age at follow-up, consistent with the findings of longitudinal studies. When age at follow-up was considered, heterogeneity was low (residual I² = 17%).

LIMITATIONS

Study quality was generally poor because randomization to hospitalization for RSV infection was not possible, appropriate blinding was rare and adjustment for confounding variables was not always appropriate.

CONCLUSIONS

The meta-analysis suggests an association between infant RSV hospitalization and respiratory morbidity that decreases with age. If the association is causal, the development of an effective vaccine against RSV could decrease the burden of asthma.

Should respiratory care in preterm infants include prophylaxis against respiratory syncytial virus infection? The case in favour

Respiratory syncytial virus (RSV) is the most significant cause of acute respiratory tract infections (RTI) in infants and young children throughout the world. Preterm infants are at increased risk for severe RSV lower respiratory tract infection due to small lung volumes, a reduced lung surface area, small airways and an increased air space wall thickness. Additionally, the airways of preterm infants have been ventilated mechanically and suctioned and potentially damaged by many microtraumas with disruption of endothelial surfaces enabling pathogens to invade more easily. The immune system of preterm infants is immature resulting in low antibody titers (incomplete transplacental transfer of maternal antibodies) and a reduced cellular immunity with reduced viral clearance. Rehospitalization rates of preterm compared to term infants due to RSV infection are increased as are total morbidity and mortality associated with RSV disease. Palivizumab effectively reduces RSV related rehospitalisation in this high-risk population.

Transmission of surfactant protein variants and haplotypes in children hospitalized with respiratory syncytial virus

Severity of lung injury with respiratory syncytial virus (RSV) infection is variable and may be related to genetic variations. This preliminary report describes a prospective, family-based association study of children hospitalized secondary to RSV, aimed to determine whether intragenic and other haplotypes of surfactant proteins (SP)-A and SP-D are transmitted disproportionately from parents to offspring with RSV disease. Genomic DNA was genotyped for several SP-A and SP-D single nucleotide polymorphisms (SNPs). Transmission disequilibrium test analysis was used to determine transmission of variants and haplotypes from parents to affected offspring. Three hundred seventy-five individuals were studied, including 148 children with active RSV disease and one or both parents. The SP-A2 intragenic haplotype 1A was found to be protective (p = 0.013). The SP-D SNP DA160_A may possibly be an "at-risk" marker (p = 0.0058). Additional two- and three-marker haplotypes were associated with severe RSV disease, with two being protective (DA11_T/DA160_G and DA160_G/SP-A2 1A/SP-A1 6A). We conclude that there may be associations between SP-A and SP-D and RSV disease. Further study is required to determine whether these variants can be used to target a high-risk patient population in clinical trials aimed at reducing either the symptoms of acute infection or long-term pulmonary sequelae.

Understanding the mechanisms of viral induced asthma: new therapeutic directions

Asthma is a common and debilitating disease that has substantially increased in prevalence in Western Societies in the last 2 decades. Respiratory tract infections by respiratory syncytial virus (RSV) and rhinovirus (RV) are widely implicated as common causes of the induction and exacerbation of asthma. These infections in early life are associated with the induction of wheeze that may progress to the development of asthma. Infections may also promote airway inflammation and enhance T helper type 2 lymphocyte (Th2 cell) responses that result in exacerbations of established asthma. The mechanisms of how RSV and RV induce and exacerbate asthma are currently being elucidated by clinical studies, in vitro work with human cells and animal models of disease. This research has led to many potential therapeutic strategies and, although none are yet part of clinical practise, they show much promise for the prevention and treatment of viral disease and subsequent asthma.

Asthma, lung function and sensitization in school children with a history of bronchiolitis

BACKGROUND

The purpose of the present retrospective study was to investigate the association of school-age asthma with acute-bronchiolitis and examine the influence of potential risk factors.

METHODS

One hundred and eighty-nine children aged 7.5 +/- 2.2 years consecutively hospitalized for respiratory syncytial virus (RSV)-positive acute bronchiolitis during infancy were evaluated by clinical examination and measurement of peak expiratory flow (PEFR), spirometry, IgE and skin-prick testing. Their pulmonary function was compared with that of 60 non-asthmatic matched controls.

RESULTS

Of the entire cohort 57.1% were diagnosed as asthmatic. PEFR, the 1-second forced expiratory volume and forced expiratory flow of 50% vital capacity of children with a history of acute bronchiolitis were statistically significantly lower than in the control group (all P < 0.001). All the aforementioned measurements of children with/without asthma were also significantly lower than controls, while values of asthmatics were significantly lower than those of non-asthmatics. The incidence of asthma in childhood was independently associated with breast-feeding <3 months (adjusted odds ratio [aOR], 8.4; 95% confidence interval [CI]: 3.1-22.4), at least one positive skin prick test (aOR, 7.1; 95%CI: 2.8-18.1), male gender (aOR, 5.0; 95%CI: 2.2-11.5), evidence of moisture in the home environment (aOR, 2.9; 95%CI: 1.3-6.3) and presence of more than one house-resident smoking indoors (aOR, 4.9; 95%CI: 1.8-9.2).

CONCLUSION

Children with a history of RSV-bronchiolitis during infancy have an increased risk for developing asthma in childhood, which was independently associated with male gender, breast-feeding <3 months, living in a home environment with moisture damage and/or tobacco smoke by two or more residents and sensitization to at least one aeroallergen. Children with a history of RSV bronchiolitis in infancy had lower spirometry in comparison to matched control group. The difference was more marked for asthmatic ones but remained significant even for non-asthmatic children.

Maternal asthma and maternal smoking are associated with increased risk of bronchiolitis during infancy

OBJECTIVE

Our goal was to determine whether maternal asthma and maternal smoking during pregnancy are associated with the incidence and severity of clinically significant bronchiolitis in term, otherwise healthy infants without the confounding factors of small lung size or underlying cardiac or pulmonary disease.

PATIENTS AND METHODS

We conducted a population-based retrospective cohort study of term, non-low birth weight infants enrolled in the Tennessee Medicaid Program from 1995 to 2003. The cohort of infants was followed through the first year of life to determine the incidence and severity of bronchiolitis as determined by health care visits and prolonged hospitalization.

RESULTS

A total of 101,245 infants were included. Overall, 20% of infants had > or = 1 health care visit for bronchiolitis. Compared with infants with neither factor, the risk of bronchiolitis was increased in infants with maternal smoking only, maternal asthma only, or both. Infants with maternal asthma only or with both maternal smoking and asthma had the highest risks for emergency department visits and hospitalizations. Infants with a mother with asthma had the highest risk of a hospitalization > 3 days, followed by infants with both maternal asthma and smoking, and maternal smoking only.

CONCLUSIONS

Maternal asthma and maternal smoking during pregnancy are independently associated with the development of bronchiolitis in term, non-low birth weight infants without preexisting cardiac or pulmonary disease. The risk of bronchiolitis among infants with mothers who both have asthma and smoke during pregnancy is approximately 50% greater than that of infants with neither risk factor. Efforts to decrease the illness associated with these 2 risk factors will lead to decreased morbidity from bronchiolitis, the leading cause of hospitalization for severe lower respiratory tract infections during infancy.

Bronchiolitis to asthma: a review and call for studies of gene-virus interactions in asthma causation

Viral infections are important causes of asthma exacerbations in children, and lower respiratory tract infections (LRTIs), caused by viruses such as respiratory syncytial virus (RSV) and rhinovirus (RV), are a leading cause of bronchiolitis in infants. Infants hospitalized with bronchiolitis are at significantly increased risk for both recurrent wheezing and childhood asthma. To date, studies addressing the incidence of asthma after bronchiolitis severe enough to warrant hospitalization have focused almost exclusively on RSV, but a number of recent studies suggest that other respiratory pathogens, including RV, may contribute as well. It is not known whether viral bronchiolitis directly contributes to asthma causation or simply identifies infants at risk for subsequent wheezing, as from an atopic predisposition or preexisting abnormal lung function. Alternatively, the properties of the infecting virus may be important. Thus, many possible determinants exist that may contribute to the severity of bronchiolitis and the subsequent development of asthma. One such determinant is the potential involvement of genetic susceptibility loci to asthma after viral bronchiolitis, a critical area that is just beginning to be evaluated. By clarifying the roles of both host- (genetic) and virus- (environment) specific factors that contribute to the frequency and severity of viral LRTI, it may be possible to determine if severe LRTIs cause asthma, or if asthma susceptibility predisposes patients to severe LRTI in response to viral infection. Characterizing these relationships offers the potential of identifying at-risk hosts in whom preventing or delaying infection could alter the phenotypic expression of asthma.

The relationship between respiratory syncytial virus infections and the development of wheezing and asthma in children

PURPOSE OF REVIEW

The relationship between respiratory syncytial virus lower-respiratory-tract infections in early childhood and asthma has been the subject of much debate. Most, but not all, previous cohort studies have failed to identify a link between early respiratory syncytial virus infection and atopic asthma. Recent studies have helped clarify some apparently contradictory findings.

RECENT FINDINGS

Cohort studies focusing on wheezing in early childhood have indicated that this is associated with an increased incidence of atopic asthma but that this risk is not increased by respiratory syncytial virus infection. Indeed, wheeze associated with rhinovirus infection may be a better marker for possible asthma. In contrast, there is no increased risk of atopic disease in infants with respiratory syncytial virus 'acute bronchiolitis', a phenotype characterized by widespread crepitation. Post-bronchiolitic symptoms are associated with intercurrent viral infections in particular and the incidence of symptoms falls rapidly during infancy.

SUMMARY

These studies confirm earlier suggestions that the phenotype of respiratory illness and hence the host response rather than the infecting organism is the best predictor of the future pattern of respiratory illness. Such considerations must be central to the design of any future intervention or cohort studies.

The role of the respiratory syncytial virus in airway syndromes in childhood

The majority of infants admitted to hospital in infancy with lower respiratory tract infections (LRTIs) have been infected with the respiratory syncytial virus (RSV). Infants and young children experiencing RSV LRTIs experience increased respiratory morbidity in subsequent years, although the prevalence falls rapidly in early childhood. Recent data support the suggestion that in most subjects, this recurrent morbidity is not attributable to atopic asthma and that in most respects, the acute and long-term outcomes with RSV infections are similar in nature to those attributable to other viruses. The phenotype of the acute illness probably provides better prognostic information than the type of virus.

The link between bronchiolitis and asthma

Bronchiolitis and asthma are common wheezing illnesses of childhood. Respiratory syncytial virus is the main causative agent of Bronchiolitis. Rhinovirus is the most common trigger of exacerbations of asthma, but also has been detected increasingly in doing children with Bronchiolitis. Reportedly, childhood asthma develops in 40% of children with a history of Bronchiolitis. No convincing link has been reported between Bronchiolitis and development of atopy, although atopy generally is regarded as the main risk factor for chronic asthma. This article focuses on the association between bronchiolitis and the development of asthma. The authors address the question how respiratory syncytial virus and rhinovirus infections in young children, together with genetics and immunologic immaturity, may contribute to the development of asthma.

Hospitalization for RSV bronchiolitis before 12 months of age and subsequent asthma, atopy and wheeze: a longitudinal birth cohort study

Several epidemiological studies have reported recurrent wheezing and asthma in children after respiratory syncytial virus (RSV) bronchiolitis in infancy. The relationship with allergic sensitization is less clear and recent evidence suggests an interaction between atopy and RSV infection in the development of asthma. Data from a large, population-based, birth-cohort (Avon Longitudinal Study of Parents and Children) were used to compare outcomes of children according to whether or not they had been admitted to hospital in the first 12 months with RSV-proven bronchiolitis. Outcomes considered were 12-month prevalence of wheeze at two ages (between 30-42 and 69-81 months), cumulative prevalence of doctor-diagnosed asthma at 91 months and skin prick test defined atopy at 7 yr. Multivariable logistic regression models were used to calculate odds ratios for outcomes adjusted for potential confounders. A total of 150 infants (1.1% of the cohort) were admitted to hospital within 12 months of birth with RSV bronchiolitis. The prevalence of wheezing was 28.1% in the RSV group and 13.1% in controls at 30-42 months and 22.6% vs. 9.6% at 69-81 months. The cumulative prevalence of asthma was 38.4% in the RSV group and 20.1% in controls at 91 months. Atopy was found in 14.6% of the RSV group and in 20.7% of controls at 7 yr. RSV bronchiolitis was associated with subsequent wheezing between 30-42 (Odds ratio [95% CI] 2.3 [1.3, 3.9]) and 69-81 months (OR 3.5 [1.8, 6.6]) and with the cumulative prevalence of asthma at 91 months (OR 2.5 [1.4, 4.3]) but not with atopy (OR 0.7 [0.2, 1.7]). In a population-based birth cohort, RSV bronchiolitis was associated with subsequent wheezing and asthma but not with the development of atopy by age 7 yr.

Pathogenesis of respiratory syncytial virus bronchiolitis-related wheezing

Respiratory syncytial virus (RSV) is a common cause of virus infection of the human respiratory tract during the first two years of life, with virtually all children experiencing at least one infection within this period. Although this usually leads to mild respiratory illness, some infants develop more severe disease (bronchiolitis, pneumonia, etc.) affecting the lower airways and frequently requiring hospitalisation. There is evidence that bronchiolitis hospitalisations have increased during the last two decades and many of the hospitalised children develop wheezing later in life. The immune response to the virus is probably a major factor in the development or the expression of the pathological phenotype. In particular, a bias towards type-2 cytokine responses seems to be associated with more severe disease, whereas a type-1 response leads to more effective viral clearance and milder illness. Although the virus by itself triggers a type-1 response, a preexisting type-1 deficiency may contribute to the severity of the disease. In that sense, RSV bronchiolitis may serve as a marker, reflecting predisposition of the individual for virus induced wheezing early in life and/or asthma later in life.

Association of an early respiratory syncytial virus infection and atopic allergy

BACKGROUND

Respiratory syncytial virus (RSV) causes postbronchiolitic wheezing but its role in allergic sensitization is controversial. The purpose of the study was to examine the effect of an early RSV infection on allergic sensitization.

METHODS

Seventy-six subjects were examined 6-10 years after hospitalization for RSV infection during the first year of life. Fifty-one subjects (68%) attended clinical studies and 25 filled in a questionnaire. The study protocol included lung function, skin-prick and blood tests. The controls were matched for birth date and sex.

RESULTS

Eight per cent of the subjects and 37% of the controls had at least one positive skin-prick test (SPT) (difference -35%, 95% CI -50 to -19%, P < 0.0001). Allergic rhinitis, atopic dermatitis and asthma occurred as often in both groups, but asthma had been diagnosed significantly earlier in the subjects than in the controls [mean age 3.0 years (SD 2.6) and 5.6 years (SD 3.0), difference 2.6 years, 95% CI 0.57-4.65, P = 0.014]. In a logistic regression analysis, RSV infection was associated with negative SPTs.

CONCLUSIONS

An early RSV infection results in reduction of SPT positivity but not of occurrence of atopic diseases. This finding might explain why there is less atopic sensitization in countries with a greater probability of acquiring RSV infection at an early age.

Current treatment for acute viral bronchiolitis in infants

This paper provides an update and critical review of available data on the treatment of acute viral bronchiolitis in previously healthy infants, with special focus on new or promising therapies. The main potential benefits of medical assistance in these patients reside in the careful monitoring of their clinical status, the maintenance of adequate hydration and oxygenation, the preservation of the airway opened and cleared of secretions and the option to perform parental education. There is no convincing evidence that any other form of therapy will reliably provide beneficial effects in infants with bronchiolitis and currently, any treatment beyond supportive care should be prescribed on a case-by-case basis with watchful appraisal of its effects. Therapies such as ribavirin, IFN, vitamin A, antibiotics, mist therapy or anticholinergics, have not demonstrated any measurable clinical effect. Several studies and meta-analyses with beta(2)-agonists and corticosteroids have failed to show any benefit of significant extent, however, physicians keep favouring their use. Presently, adrenaline has received rather consistent support from clinical trials but it is not yet widely prescribed. There are other therapeutic strategies, for instance, heliox, hypertonic saline, noninvasive ventilation, physical therapy techniques, thickened feeds or palivizumab that have shown promising potential benefits, but evidence supporting its use is still limited and further studies should be warranted. In the meantime, infants with acute viral bronchiolitis should be treated following evidence-based clinical practice guidelines, keeping the patient central in the process and being sensitive to social, cultural and familiar influences on their treatment strategy.

Current concepts on active immunization against respiratory syncytial virus for infants and young children

Respiratory syncytial virus (RSV) is the most important causative agent of viral respiratory tract infections in infants and young children. Passive immunization against RSV became available recently, but this does not apply to an effective vaccine as a result of dramatic adverse results of immunization with a RSV candidate vaccine in the 1960s and the lack of full knowledge of the immune response induced by RSV. Nonetheless intensive research during the past two decades has resulted in several interesting candidate vaccines, of which some have gone through testing in humans. These include the subunit vaccines PFP-1, PFP-2, BBG2Na and cold-passaged/temperature-sensitive mutants. The development of candidate vaccines against RSV is discussed. Because of questions, uncertainties and difficulties with the development of effective vaccines against RSV, it will probably be at least another 5 to 10 years before routine immunization against RSV becomes available.

Pathophysiological mechanisms for the respiratory syncytial virus-reactive airway disease link

There is substantial epidemiological evidence supporting the concept that respiratory syncytial virus (RSV) lower respiratory tract infection in infancy may be linked to the development of reactive airway disease (RAD) in childhood. However, much less is known concerning the mechanisms by which this self-limiting infection leads to airway dysfunction that persists long after the virus is cleared from the lungs. A better understanding of the RSV-RAD link may have important clinical implications, particularly because prevention of RSV lower respiratory tract infection may reduce the occurrence of RAD later in life. Among the mechanisms proposed to explain the chronic sequelae of RSV infection is the interaction between the subepithelial neural network of the airway mucosa and the cellular effectors of inflammatory and immune responses to the virus. The body of clinical literature linking RSV and RAD is reviewed herein, as are the cellular and molecular mechanisms of neuroimmune interactions and neural remodeling that may underlie this link, and the possibility that preventing the infection may result in a decreased incidence of its chronic sequelae.

Clinical perspectives on the association between respiratory syncytial virus and reactive airway disease

Asthma is a leading cause of morbidity and mortality among children worldwide, as is respiratory syncytial virus (RSV). This report reviews controlled retrospective and prospective studies conducted to investigate whether there is an association between RSV bronchiolitis in infancy and subsequent development of reactive airway disease or allergic sensitization. Findings indicate that such a link to bronchial obstructive symptoms does exist and is strongest for children who experienced severe RSV illness that requires hospitalization. However, it is not yet clear what roles genetic predisposition and environmental or other risk factors may play in the interaction between RSV bronchiolitis and reactive airway disease or allergic sensitization. Randomized, prospective studies utilizing an intervention against RSV, such as a passive immunoprophylactic agent, may determine whether preventing RSV bronchiolitis reduces the incidence of asthma.

Novel pathways in the pathogenesis of respiratory syncytial virus disease

Respiratory syncytial virus (RSV) is a leading cause of severe respiratory infections in infants and children. Extensive research in past decades has expanded our knowledge regarding the specific mechanisms involved in the pathogenesis of RSV bronchiolitis and subsequent chronic obstructive airway disease. Studies of RSV infection are performed in humans, cell culture models, and animal models, each with their own specific limitations. A recently developed murine model in which pulmonary dysfunction can be monitored and quantified appears to add a powerful tool for the study of specific pathogenic mechanisms of experimental RSV infections. Both immunologic and nonimmunologic factors have been implicated in the pathogenesis of RSV-induced diseases. Recently, a hypothesis that RSV bronchiolitis may be the result of production of Th2-type cytokines has become popular. There are, however, studies in human infants with RSV as well as in RSV-infected mice that suggest this theory is incorrect, or at least an oversimplification. There is compelling evidence that cells producing interferon gamma may contribute to RSV-induced wheezing, possibly through induction of leukotriene release. Among the nonimmunologic factors, pulmonary surfactant has recently attracted attention, especially because of the therapeutic implications for infants with severe bronchiolitis. A better understanding of the pathogenesis of RSV-induced diseases will be of considerable help in developing specific therapeutic strategies and in vaccine development.

Respiratory syncytial virus bronchiolitis in infancy is an important risk factor for asthma and allergy at age 7

We previously reported an increased risk for bronchial obstructive disease and allergic sensitization up to age 3 in 47 children hospitalized with a respiratory syncytial virus (RSV) bronchiolitis in infancy compared with 93 matched control subjects recruited during infancy. The aims of the present study were to evaluate the occurrences of bronchial obstructive disease and allergic sensitization in these children at age 7(1)/ (2). All 140 children reported for the follow-up, which included physical examination, skin prick tests, and serum IgE tests for common food and inhaled allergens. The cumulative prevalence of asthma was 30% in the RSV group and 3% in the control group (p < 0.001), and the cumulative prevalence of "any wheezing" was 68% and 34%, respectively (p < 0.001). Asthma during the year prior to follow-up was seen in 23% of the RSV children and 2% in the control subjects (p < 0.001). Allergic sensitization was found in 41% of the RSV children and 22% of the control subjects (p = 0.039). Multivariate evaluation of possible risk factors for asthma and sensitization using a stepwise logistic statistical procedure for all 140 children showed that RSV bronchiolitis had the highest independent risk ratio for asthma (OR: 12.7, 95% CI 3.4 to 47.1) and a significantly elevated independent risk ratio for allergic sensitization (OR: 2.4, 95% CI 1.1 to 5.5). In conclusion, RSV bronchiolitis in infancy severe enough to cause hospitalization was highly associatied with the development of asthma and allergic sensitization up to age 7(1)/ (2). The results support the theory that the RSV influences the mechanisms involved in the development of asthma and allergy in children.

Randomised controlled trial of budesonide for the prevention of post-bronchiolitis wheezing

BACKGROUND

Previous studies suggest that recurrent episodes of coughing and wheezing occur in up to 75% of infants after acute viral bronchiolitis.

AIM

To assess the efficacy of budesonide given by means of a metered dose inhaler, spacer, and face mask in reducing the incidence of coughing and wheezing episodes up to 12 months after acute viral bronchiolitis.

METHODS

Children under the age of 12 months admitted to hospital with acute viral bronchiolitis were randomised to receive either budesonide or placebo (200 microg or one puff twice daily) for the next eight weeks. Parents kept a diary card record of all episodes of coughing and wheezing over the next 12 months.

RESULTS

Full follow up data were collected for 49 infants. There were no significant differences between the two study groups for the number of infants with symptom episodes up to six months after hospital discharge. At 12 months, 21 infants in the budesonide group had symptom episodes compared with 12 of 24 in the placebo group. The median number of symptom episodes was 2 (range, 0-13) in those who received budesonide and 1 (range, 0-11) in those who received placebo. Because there is no pharmacological explanation for these results, they are likely to be caused by a type 1 error, possibly exacerbated by there being more boys in the treatment group.

CONCLUSION

Routine administration of budesonide by means of a metered dose inhaler, spacer, and face mask system immediately after acute viral bronchiolitis cannot be recommended.

Lower airway disease caused by respiratory syncytial virus

Respiratory syncytial virus (RSV) is the most common cause of lower respiratory tract disease in infants and young children. Most infections due to RSV are mild and do not require hospitalization. RSV causes both upper respiratory tract infections as well as lower respiratory tract infections. Infants with underlying disease states like bronchopulmonary dyslasia, congenital heart disease and prematurity appear more prone to develop severe infection and have a higher incidence of hospitalization. The exact pathogenesis of RSV is not well understood. The mortality associated with primary RSV infection in healthy children is estimated to be between .005% to .02%. In hospitalized children the mortality rate is estimated to be from 1% to 3%. Several treatment modalities in the form of bronchodilators, corticosteroids, ribavirin, intravenous immune gammaglobulin and antibiotics are available. Studies have failed to show the true beneficial effect of any of the above treatment modalities. Supportive care is only needed. The best treatment is the supportive care in the form of oxygen and fluids and close monitoring of the vital signs including oxygen saturation.

Does breast feeding protect against non-gastric infections?

There is convincing evidence that breast-feeding is protective against gastro-enteritis and diarrhoea, but for other infections the situation is less clear cut. There is evidence that breast-fed infants are at increased risk of one infection (infant botulism). They are probably not significantly protected from upper respiratory tract infections (other than otitis media.), but they may be at a decreased risk of lower respiratory tract infections, particularly those associated with respiratory syncytial virus. There is strong evidence that Haemophilus influenzae B infection is more likely in the bottle-fed infant, and consistent evidence of protection of young children from chronic otitis media with prolonged breast-feeding.

Respiratory status and allergy nine to 10 years after acute bronchiolitis

In order to evaluate further the relationship between acute bronchiolitis in infancy and subsequent respiratory problems, children prospectively followed up from the time of their admission to hospital were reviewed along with a group of matched controls recruited at the previous five and a half year assessment. Sixty one index children and 47 controls took part. The groups were well matched for age, height, parental smoking, and social class. Although the prevalence of respiratory symptoms had fallen when related to the previous review, there remained an excess of coughing (48 and 17% in index and control children respectively; odds ratio 4.02) and wheezing (34 and 13% in index and control children respectively; odds ratio 3.59). Bronchodilator therapy was used by 33% of index children compared with 3% of controls. Lung function tests revealed no significant differences in the measurements of lung growth-for example, forced vital capacity, functional residual capacity, and total lung capacity-but the index children had significant reductions in measurements of airways obstruction-for example, forced expiratory volume in one second, maximum expiratory flow at 75, 50 and 25% of vital capacity, and airways resistance. Family history and personal skin tests showed no excess of atopy in the index group. This study supports the claim that the excess respiratory symptoms after acute bronchiolitis are not due to familial or personal susceptibility to atopy.

Tryptase and IgE concentrations in the respiratory tract of infants with acute bronchiolitis

It has been proposed that a specific IgE response contributes to the immunopathology of acute respiratory syncytial virus (RSV) bronchiolitis but previous work has been difficult to replicate. Indirect evidence that might support this contention was sought by measuring total IgE concentrations in bronchoalveolar lavage (BAL) samples obtained from intubated infants and by attempting to detect mRNA for IgE in cells obtained from both the upper and lower respiratory tract. Evidence of significant mast cell activation was sought by measuring tryptase concentrations in BAL fluid and serum. Detectable concentrations of IgE were found in two of seven BAL samples obtained more than five days after intubation and mRNA for IgE was demonstrated in three of six BAL samples and three of six samples obtained from the upper respiratory tract. Tryptase was detectable in 11 of 12 BAL samples with the two highest values detected on day 1. These values were raised compared with control samples but were not such to suggest that mast cell degranulation is the major contributor to the inflammatory process. These results suggest that IgE may be produced in the airways of infants in response to RSV infection. The relationships between IgE production, RSV infection, and symptoms of acute bronchiolitis remain obscure.

Acute lower respiratory infection in Argentinian children: a 40 month clinical and epidemiological study

In a total of 1,003 children (805 inpatients and 198 outpatients) with acute lower respiratory infections (ALRI), clinical, social, and environmental data were analyzed. The major clinical entities were bronchiolitis, pneumonia, bronchitis, and laryngitis. The first two of these predominated in inpatients; pneumonia and bronchitis were more common in older children, while bronchiolitis was observed in infants. Respiratory rates of > 50/min. were more common in younger children and in cases with bronchiolitis and bronchitis. Retractions showed markedly less age-dependent variations and were present in all severe cases with different clinical diagnoses. Retractions alone or associated with cyanosis were the best indicators for severity of ALRI. Among outpatients, fever and wheezing were more common; inpatients were younger, more frequently malnourished, and from a lower socioeconomic level; family history of chronic bronchitis, crowding, and parental smoking also prevailed in this group. Family asthma and exposure to domestic aerosols was more common among outpatients. Prematurity rate (17 and 15%) of all ALRI cases was twice that of the general pediatric population and a significant difference existed between in- and outpatients under 6 months of age when perinatal respiratory pathologies predominated among inpatients. It is suggested to consider the need for assessing personal, family, and environmental risk factors in addition to clinical signs and symptoms when severe cases of ALRI are evaluated.

Serum immunoglobulin G subclasses and serum immunoglobulin A in acute bronchiolitis in infants

Serum IgG subclasses and Serum IgA were studied in 43 infants with acute bronchiolitis and 20 healthy infants. IgG subclasses were determined by a capture ELISA and IgA was quantified by turbidimetry. IgG1 concentrations were significantly lower in infants with bronchiolitis than in normal infants. The other IgG subclasses and IgA did not differ between the groups. The subgroups of infants with bronchiolitis who had previously suffered from otitis media or bronchitis, had significantly lower IgG2 than the other infants with bronchiolitis. The same was found for infants with bronchiolitis who had suffered from three or more lower respiratory tract infections. In infants who had suffered from upper or lower respiratory infections before the acute bronchiolitis, IgA was significantly higher than in infants without previous respiratory infections. Ten infants with bronchiolitis (23%) had IgG1 deficiency, that is values below the lower reference limit calculated in a population of healthy Norwegian infants. No healthy infants had any IgG1 deficiency. No infant with bronchiolitis had IgG2 or IgG3 deficiency. The low IgG1 values found in infants with acute bronchiolitis, may be one cause for infants to be more susceptible to RS virus infections.

Respiratory status and allergy after bronchiolitis

As part of a long term prospective study, 73 children who had been admitted to hospital with viral bronchiolitis as infants, were reviewed 5.5 years later and compared with a carefully matched control group. In the postbronchiolitis group, there was a highly significant increase in respiratory symptoms including wheezing (42.5% v 15.0%, relative risk = 2.8). Although atopy in the family was not significantly increased in the index group, personal atopy was more prevalent. However, personal atopy was not significantly more prevalent in the symptomatic postbronchiolitis, compared with those who were symptom free, and so did not account for the high prevalence of postbronchiolitis wheezing in this cohort. In addition, in a stepwise logistic regressional model, bronchiolitis remained a significant predictor of wheezing after adjusting for potential confounding variables, including atopy. Bronchial responsiveness to histamine was significantly increased in the index group. However, no significant relationship of positive tests to wheezing could be demonstrated, and a high rate of positive responses was noted in the controls.

Acute and long-term effects of viral bronchiolitis in infancy

About 1% of infants are admitted to hospital with acute bronchiolitis; 85% of cases are caused by infection with Respiratory Syncytial Virus (RSV). The pathophysiological changes during the acute illness are inflammatory obstruction in the small airways with submucosal cellular infiltration, epithelial necrosis and mucous plugging; FRC increases and dynamic compliance falls. Failure to respond to bronchodilator drugs suggests that muscle spasm contributes relatively little to the airway narrowing. Affected infants become increasingly dyspnoeic and hypoxic for 3-4 days then spontaneously improve. After an attack of acute bronchiolitis up to 75% of children have recurrent lower respiratory tract symptoms, many continue to have hyperinflated lungs and bronchial hyperresponsiveness. In the majority, symptoms of cough and wheezing have subsided by the time they start school, but abnormalities of small airway function are detectable at least 13 years later. Children with a genetic predisposition to atopy do not appear to have an increased risk of developing bronchiolitis. Evidence of genetic predisposition to bronchial hyperresponsiveness in those with persistent wheezing is controversial. There is little to suggest that neonatal lung damage or an adverse home environment are important factors in determining susceptibility to post-bronchiolitis wheezing. IgE antibodies to RSV, and leukotriene C4, are found more frequently in the respiratory secretions of infants who wheeze during and after bronchiolitis than in those who do not. The possibility of viral-induced alteration of the immune response at the time of infection needs further investigation.