In very young infants severity of acute bronchiolitis depends on carried viruses

Prospects for molecular point-of-care diagnosis of lower respiratory infections at the hospital’s doorstep

Now that molecular assays have been simplified, they can be performed at the point of care (POC). As we aimed to evaluate POC detection of respiratory viruses, we have collected studies on the molecular detection of viruses in children and adults with a well-characterized diagnosis, made in hospital settings, of community-acquired acute bronchiolitis (AB) or pneumonia (CAP). We then present the epidemiological issues for each disease. The prevalence of 18 virus species and types was determined separately for each disease, virus by virus. Overall, the median detection rate of viruses was 90% (interquartile range [IQR]: 69.25–93.5%) and 71.8% (IQR: 69.25–74.25%) in children with AB and CAP, respectively, and 24.5% (IQR: 20–30%) in adults with CAP. The observations on the relationship between virological findings and severity of disease were conflicting in AB, while those for influenza-related CAP were significantly associated with high morbidity/mortality. There is evidence supporting the suggestion that molecular POC detection of targeted pathogens could optimize bed management in emergency departments, guide anti-infective therapies and prevent nosocomial outbreaks. However, further investigations are required to determine when the detection of a large panel of viruses should be processed in clinical practice.

Diagnostic value of respiratory virus detection in symptomatic children using real-time PCR

Background

Acute respiratory tract infections are an important public health problem. Sensitive and rapid diagnostic techniques have been developed and are used in daily clinical practice. Here we evaluate the clinical relevance of detecting 20 common respiratory pathogens by molecular methods in a general pediatric clinic.

Methods

Nasopharynx samples of children < 18 years of age with respiratory symptoms referred to a general pediatric clinic were tested for the presence of 19 viruses and Mycoplasma pneumoniae, using real-time polymerase chain reaction.

Results

Of 177 patients included in this retrospective study, 73% were positive for at least one virus. Respiratory syncytial virus (36.6%) and human rhinovirus (24%) were most frequently detected. Patients in whom a respiratory virus or Mycoplasma pneumoniae was detected, were younger (6 versus 24 months; p < 0.001) and more often hospitalized (116 versus 34; p = 0.001) than patients in whom no respiratory pathogen was detected. Also they were more likely to present with feeding problems, dyspnea, rhinorrhea and wheezing (all p < 0.05) than patients without a respiratory pathogen.

In the majority of cases, clinicians did not change their antibiotic management after detecting a viral respiratory pathogen. No difference in mean Ct value was found between patients with one respiratory pathogen and those with >1 respiratory pathogen (30.5 versus 31.2; p = 0.573).

Conclusion

Routine testing of common respiratory pathogens could lead to a better understanding of their role in disease in children with respiratory symptoms.

Prospective multicenter study of viral etiology and hospital length of stay in children with severe bronchiolitis

OBJECTIVE

To determine whether hospital length of stay(LOS) for acute bronchiolitis is influenced by the infecting pathogen.

DESIGN

A prospective observational cohort study was performed during 3 consecutive years.

SETTING

Sixteen US hospitals participated in the study.

PARTICIPANTS

Children younger than 2 years hospitalized with bronchiolitis were included.

MAIN EXPOSURE

The results of nasopharyngeal aspirate polymerase chain reaction pathogen testing served as the main exposure.

MAIN OUTCOME MEASURE

Hospital LOS was determined.

RESULTS

Of 2207 participants, 72.0% had respiratory syncytial virus (RSV) and 25.6% had human rhinovirus(HRV); the incidence of each of the other viruses and bacteria was 7.8% or less. Multiple pathogen infections were present in 29.8% of the children. There were 1866 children(84.5%) with RSV and/or HRV. Among these 1866 children, the median age was 4 months and 59.5% were male. The median LOS was 2 days (interquartile range,1-4 days). Compared with children who had only RSV,an LOS of 3 or more days was less likely among children with HRV alone (adjusted odds ratio [AOR], 0.36; 95%CI, 0.20-0.63; P.001) and those with HRV plus non-RSV pathogens (AOR, 0.39; 95% CI, 0.23-0.66; P.001)but more likely among children with RSV plus HRV(AOR,1.33; 95% CI, 1.02-1.73; P=.04), controlling for 15 demographic and clinical factors.

CONCLUSIONS

In this multicenter study of children hospitalized with bronchiolitis, RSV was the most common virus detected, but HRV was detected in one-quarter of the children. Since 1 in 3 children had multiple virus infections and HRV was associated with LOS, these data challenge the effectiveness of current RSV-based cohorting practices, the sporadic testing for HRV in bronchiolitis research, and current thinking that the infectious etiology of severe bronchiolitis does not affect short-term outcomes.

The microarray technology: facts and controversies

Molecular diagnostic techniques for viral testing have undergone rapid development in recent years. They are becoming more widely used than the classical virological assays in the majority of clinical virology laboratories, and now represent a new method for the diagnosis of human viral infections. Recently, new techniques based on multiplex RT‐PCR amplification followed by microarray analysis have been developed and evaluated. On the basis of amplification of viral genome‐specific fragments by multiplex RT‐PCR and their subsequent detection via hybridization with microorganism‐specific binding probes on solid surfaces, they allow simultaneous detection and identification of multiple viruses in a single clinical sample. The management of viral central nervous system and respiratory tract infections currently represents the two main applications of the microarrays in routine virological practice. Microarrays have shown reliable results in comparison with those of referenced (RT)‐PCR assays, and appear to be of major interest for the detection of a broad range of respiratory and neurotropic viruses, assessment of the pathogenicity of newly discovered or neglected viruses, and identification of multiple viral infections in clinical samples. Despite several limitations observed during the different studies performed, this new technology might improve the clinical management of patients by enlarging the range of the viruses detected, in particular in cases of severe infections leading to patient hospitalization in the intensive‐care unit. They might also help in the prevention of nosocomial transmission in hospital departments by contributing to the development of new epidemiological surveillance systems for viral infections.

Broad respiratory virus detection in infants hospitalized for bronchiolitis by use of a multiplex RT-PCR DNA microarray system

Newly available molecular tools allow a sensitive detection of a broad panel of viruses in respiratory tract specimens. In the present study, the application of a multiplex RT‐PCR DNA microarray in diagnosis and epidemiological survey of viral infections in infants hospitalized for bronchiolitis was assessed. One hundred and thirty‐eight nasopharyngeal aspirates collected from October 2007 to September 2008 were tested by direct immunofluorescence and viral culture, a combination of referenced RT‐PCRs and the DNA microarray. One or more viruses were detected in 96, 126 and 126 of the specimens by direct immunofluorescence and viral culture, RT‐PCRs and DNA microarray, respectively (70 vs. 91 vs. 91%, P < 10⁻³). The RT‐PCRs and the DNA microarray yielded concordant results for 99% of specimens and identified mixed viral infections in 85 (62%). The most common associations were: human bocavirus and respiratory syncytial virus (32%), adenovirus and respiratory syncytial virus (30%), and parainfluenza virus type 3 and respiratory syncytial virus (23%). None of the bronchiolitis severity parameters including intensive care unit admission, O₂ supply, O₂ saturation percentage, O₂ length and length of stay at the hospital appeared to be significantly increased in multiple viral infections compared to single viral infections (P > 0.1). In conclusion, the use of this DNA microarray in clinical virology practice allows rapid and accurate identification of common and uncommon viral respiratory pathogens in infants hospitalized for bronchiolitis. It should improve the clinical management, the epidemiological survey, and the prevention of the nosocomial transmission of respiratory viruses in pediatric wards. J. Med. Virol. 84:979–985, 2012. © 2012 Wiley Periodicals, Inc.

Viral epidemiology and severity of respiratory infections in infants in 2009: a prospective study

BACKGROUND

Viral respiratory infections are common in infants and can be severe. The new pandemic influenza virus H1N1v2009 was feared to cause particularly severe outcomes.

OBJECTIVE

This study aimed at evaluating the impact of H1N1v2009 on the viral epidemiology, the clinical presentation and the severity of respiratory infections in infants.

PATIENTS AND METHODS

This prospective epidemiologic study included all infants <2 years of age, both inpatients and outpatients, presenting with respiratory symptoms, from November 2009 through April 2010, at the pediatric emergency department of the University Hospital of Caen, France. A nasal swab was taken for viral detection and analyzed by immunofluorescence and, if negative, polymerase chain reaction. Severe respiratory infection was defined by a score of respiratory severity.

RESULTS

One thousand twenty-one infectious episodes with a respiratory sample met inclusion criteria. Eight hundred thirty-four samples (81.7%) were positive. The viruses with the highest incidence were the respiratory syncytial virus (34.2%), the rhinoviruses (23.9%), the coronaviruses (9.3%) and H1N1v2009 (7.7%). Of all infections, 28.6% were severe and more frequent in infants with risk factors. H1N1v2009 infections had a low risk of severe respiratory disease (odds ratios = 0.15) and hospitalization (odds ratios = 0.40) compared with the other viruses. Respiratory syncytial virus infections had a high risk of respiratory severity (odds ratios = 7.85) and were responsible for 71.4% of admissions to the intensive care unit.

CONCLUSION

Despite the modest impact of H1N1v2009 observed in this study, further surveillance is needed to detect virological factors that may increase its severity.

What is the clinical relevance of respiratory syncytial virus bronchiolitis?: findings from a multi-center, prospective study

Acute bronchiolitis (AB) is caused primarily by respiratory syncytial virus (RSV). Recent laboratory tools have implicated a variety of other pathogens; however, their clinical relevance has not been clearly defined. The purpose of this study was to determine whether the etiological agents of AB affect its course. A multicenter prospective study was performed in previously healthy children <24 months of age who presented with <4 days duration of AB. Subjects were divided into the following groups: "only RSV," "also RSV," "no RSV," and "no pathogen." The clinical severity score on admission as well as the overall severity of disease was assessed. RSV was the most common cause of AB (77.5 %). "Only RSV" or "also RSV" patients had a higher clinical score on admission compared to those with "no RSV," p < 0.001 and p < 0.02, respectively. "Only RSV" and "also RSV" patients had a higher disease severity score when compared to patients with "no RSV," 5.9 ± 1.4 vs. 5.1 ± 1.5, p < 0.001, and 5.6 ± 1.4 vs. 5.1 ± 1.5, p < 0.02, respectively. Disease severity did not vary as a function of transfer to the pediatric intensive care unit (PICU) or duration of supplemental oxygen, yet, "only RSV" was associated with a longer length of stay (LOS) than "no RSV," p < 0.02. "Only RSV"-related AB was associated with a more severe initial clinical presentation and a longer LOS. There appears to be little immediate clinical benefit to diagnosing RSV AB to the individual patient, but the application of these diagnostic methods may have significant cost-saving implications and, thus, deserves consideration by medical professionals and health policy analysts.

Hospitalizations for respiratory syncytial virus bronchiolitis in preterm infants at <33 weeks gestation without bronchopulmonary dysplasia: the CASTOR study

This study was conducted during the 2008–2009 respiratory syncytial virus (RSV) season in France to compare hospitalization rates for bronchiolitis (RSV-confirmed and all types) between very preterm infants (<33 weeks' gestational age, WGA) without bronchopulmonary dysplasia and full-term infants (39–41 WGA) matched for date of birth, gender and birth location, and to evaluate the country-specific risk factors for bronchiolitis hospitalization. Data on hospitalizations were collected both retrospectively and prospectively for 498 matched infants (249 per group) aged <6 months at the beginning of the RSV season. Compared to full-term infants, preterm infants had a fourfold [95% confidence interval (CI) 1·36–11·80] and a sevenfold (95% CI 2·79–17·57) higher risk of being hospitalized for bronchiolitis, RSV-confirmed and all types, respectively. Prematurity was the only factor that significantly increased the risk of being hospitalized for bronchiolitis. The risk of multiple hospitalizations for bronchiolitis in the same infant significantly increased with male gender and the presence of siblings aged ⩾2 years.

Comparison of risk factors for human metapneumovirus and respiratory syncytial virus disease severity in young children

Background. Human metapneumovirus (hMPV) and respiratory syncytial virus (RSV) are leading pediatric pathogens. However, risk factors for severe hMPV disease remain unknown. We comparatively assessed environmental, host, and viral determinants for severe hMPV and RSV infections.

Methods. We studied a prospective cohort of >1000 children aged <3 years hospitalized in or presenting to a pediatric clinic for acute respiratory infection. We collected clinical data at enrollment and 1-month follow-up and tested nasopharyngeal secretions for respiratory viruses. Disease severity was defined as hospitalization and was also assessed with a severity score (1 point/variable) calculated on the basis of fraction of inhaled O₂ ≥ 30%, hospitalization >5 days, and pediatric intensive care unit admission.

Results. hMPV was identified in 58 of 305 outpatient children (19.0%) and 69 of 734 hospitalized children (9.4%), second only to RSV (48.2% and 63.6%, respectively). In multivariate regression analysis of hMPV cases, age <6 months and household crowding were associated with hospitalization. Among hospitalized patients, risk factors for severe hMPV disease were female sex, prematurity, and genotype B infection. Age <6 months, comorbidities, and household crowding were risk factors for RSV hospitalization; breast-feeding and viral coinfection were protective. Age <6 months and prematurity were associated with severe RSV cases among hospitalized children.

Conclusions. hMPV and RSV severity risk factors may differ slightly. These findings will inform hMPV prevention strategies.

Prospective evaluation of clinical scoring systems in infants with bronchiolitis admitted to the intensive care unit

The objective of this investigation was to compare different scoring systems to assess the severity of illness in infants with bronchiolitis admitted to a tertiary paediatric intensive care unit (PICU). Over an 18-year period (1990-2007), infants with bronchiolitis aged up to 12 months and admitted to the PICU were prospectively scored using the Pediatric Risk of Mortality III (PRISM III) score, the Organ System Failure (OSF) score and the Acute Physiologic Score for Children (APSC) within 24 h. Infants were compared as to whether or not bronchiolitis was associated with respiratory syncytial virus (RSV). There was no difference between 113 RSV-positive and 80 RSV-negative infants regarding gestational age, birth weight, rate of premature delivery or bronchopulmonary dysplasia (BPD). The PRISM III score differed significantly between RSV-positive and RSV-negative cases (3.27 ± 0.39 vs. 1.96 ± 0.44, p = 0.006), as did the OSF score (0.56 ± 0.05 vs. 0.35 ± 0.06, p = 0.049) and the APSC (5.16 ± 0.46 vs. 4.1 ± 0.53, p = 0.048). All scores were significantly higher in the subgroup with mechanical ventilation (p < 0.0001). The mean time of ventilation was significantly higher in the RSV-positive group compared to the RSV-negative group (6.39 ± 1.74 days vs. 2.4 ± 0.47 days, p < 0.001). Infants suffering from RSV-positive bronchiolitis had higher clinical scores corresponding with the severity of bronchiolitis.

Infection with multiple viruses is not associated with increased disease severity in children with bronchiolitis

BACKGROUND

The clinical relevance of parallel detection of multiple viruses by real-time polymerase chain reaction (RT-PCR) remains unclear. This study evaluated the association between the detection of multiple viruses by RT-PCR and disease severity in children with bronchiolitis.

METHODS

Children less than 2 years of age with clinical symptoms of bronchiolitis were prospectively included during three winter seasons. Patients were categorized in three groups based on disease severity; mild (no supportive treatment), moderate (supplemental oxygen and/or nasogastric feeding), and severe (mechanical ventilation). Multiplex RT-PCR of 15 respiratory viruses was performed on nasopharyngeal aspirates.

RESULTS

In total, 142 samples were obtained. Respiratory Syncytial virus (RSV) was the most commonly detected virus (73%) followed by rhinovirus (RV) (30%). In 58 samples (41%) more than one virus was detected, of which 41% was a dual infection with RSV and RV. In RSV infected children younger than 3 months, disease severity was not associated with the number of detected viruses. Remarkably, in children older than 3 months we found an association between more severe disease and RSV mono-infections.

CONCLUSION

Disease severity in children with bronchiolitis is not associated with infection by multiple viruses. We conclude that other factors, such as age, contribute to disease severity to a larger extent.

Incidence and predisposing factors for severe disease in previously healthy term infants experiencing their first episode of bronchiolitis

AIM

To determine the incidence and predisposing factors for severe bronchiolitis in previously healthy term infants <12 months of age experiencing their first episode of bronchiolitis.

METHODS

Epidemiological, clinical and virological data were prospectively collected. Severity was assessed by the need for ventilatory support.

RESULTS

Of the 310 infants enrolled, 16 (5.1%) presented with severe bronchiolitis requiring ventilatory support (11 since admission). Compared with infants with less severe bronchiolitis, infants with severe disease presented with lower birth weight, gestational age, postnatal weight and postnatal age, and were more likely to be born by cesarian section. C-reactive protein positive results (>0.8 mg/dL) and pulmonary consolidation on chest X-ray were more common among infants with severe disease. Severity was independently associated with younger age on admission <30 days, respiratory syncytial virus (RSV) infection and lymphocyte counts < 3200/μL. No significant differences were found between epidemiologic variables.

CONCLUSIONS

Severe bronchiolitis is uncommon in previously healthy term infants <12 months of age and when present develops soon after disease onset. Severity is predicted by young age and RSV carriage, whereas epidemiologic variables seem less likely to intervene.

Viral etiology of acute febrile respiratory illnesses in hospitalized children younger than 24 months

BACKGROUND

Respiratory infections are a leading cause of pediatric hospitalizations. This study investigated whether virus-virus or virus-Bordetella co-infections are more frequent or more severe than previously recognized.

METHODS

This is a 3-year prospective study of children younger than 24 months hospitalized with a febrile respiratory illness. Viral pathogens were detected using multiplex polymerase chain reaction (PCR), enzyme-linked immunoassays, and/or viral cultures from nasopharyngeal samples. Bordetella infections were detected by PCR.

RESULTS

A total of 201 patients were enrolled. Respiratory viruses were detected in 187 (93%) patients, with 52 (28%) multipathogen infections. The most common viruses detected were respiratory syncytial virus and rhinovirus/enterovirus. There were no differences in illness severity when comparing patients infected with one pathogen and those with multipathogen infection.

CONCLUSION

Virus co-infection in young children hospitalized with an acute febrile respiratory infection is common but does not appear to be associated with illness severity.

Viral bronchiolitis for the clinician

Viral bronchiolitis is common, and about 98-99% of infants are managed in the home. Because about 95% of infants < 2 years old are infected with respiratory syncytial virus, however, bronchiolitis is the commonest reason for admission to hospital in the first 6 months of life. It is usually a self-limiting condition lasting around a week in previously well children. About 1% of infants are admitted to hospital, and about 10% of hospitalised infants will require admission to the intensive care unit. Respiratory syncytial virus is isolated from about 70% of infants hospitalised with bronchiolitis. The emphasis of hospital treatment is to ensure adequate hydration and oxygenation. Other than supplemental oxygen, little in the way of pharmacological treatment has been demonstrated to alter the course of the illness or the risk of wheezing in the months following bronchiolitis.

Respiratory viruses in children admitted to hospital intensive care units: evaluating the CLART® Pneumovir DNA array

Viruses play a significant part in children's respiratory infections, sometimes leading to hospitalization in cases of severe respiratory distress. The aim of this study was to investigate respiratory infections in children treated in a hospital intensive care unit (ICU). Assays were performed using the CLART® Pneumovir DNA array assay (Genomica, Coslada, Madrid, Spain), which makes it possible to detect 11 genus of respiratory viruses simultaneously. During the winter of 2008–2009, 73 respiratory specimens collected from 53 children under 2 years of age and admitted to an ICU were tested. At least one virus was detected in 78% (57/73) of the samples. The virological diagnosis was based on single infections in 65% (37/57) and on multiple infections in 35% (20/57) of cases. The array assay revealed respiratory syncytial virus (RSV) in 73.6% (42/57) of the samples and rhinovirus in 24.6% (14/57), either on their own or in co‐infections. All viruses identified in single and multiple infections were tested, taking into account clinical features, risk factors, and severity criteria. Children with no risk factors presented more multiple infections, up to 42% of cases, than children with at least one risk factor. RSV seemed to induce severe symptoms by itself as no difference in intubation needs was observed when RSV was detected on its own or in co‐infection. The CLART® Pneumovir DNA array was useful for examining severe viral respiratory infections, when other viruses than those detected by conventional methods could be involved, particularly in an ICU. J. Med. Virol. 83:150–155, 2011. © 2010 Wiley‐Liss, Inc.

The distinguishing features of human metapneumovirus and respiratory syncytial virus

Acute respiratory tract infections (RTIs) are a leading cause of morbidity and mortality worldwide. Human Metapneumovirus (hMPV) is a member of the Metapneumovirus genus within the Pneumovirinae subfamily of the Paramyxoviridae family. Though hMPV was only discovered in 2001, a large body of work has already shown that it is the aetiologic agent of a substantial proportion of upper and lower RTIs across all age groups in both healthy and immunocompromised hosts throughout the world. RSV, also a pneumovirus, is the human pathogen most closely related to hMPV. RSV is the leading cause of pneumonia and bronchiolitis in infants and young children, but can also cause respiratory tract disease in all age groups. In this paper, we will review the salient features of the virology, epidemiology, pathogenesis, host immune responses, clinical manifestations and diagnostic modalities of hMPV, using RSV as a comparison. In addition, we will show how immunoprophylactic and therapeutic strategies studied and used in clinical practice for RSV-some with great success, and others tragic failure-have led to promising areas of research for the prevention and treatment of the significant burden of disease caused by hMPV.

[Bronchiolitis viruses]

In Normandy (France), human respiratory syncytial virus (hRSV) was detected in 64.1% of acute bronchiolitis in hospitalized children, rhinovirus in 26.8%, human metapneumovirus (hMPV) in 7.6%, and parainfluenza virus (PIV) in 3.4%. The viruses causing acute bronchiolitis in the community were hRSV (42%), rhinovirus (19.5%), coronavirus (8%), PIV (3.5%), and hMPV (2.5%). In 53.7% of the cases, hRSV infected infants (86.9%), 53.7% being less than 6 months of age. Of the hRSV cases, 48.2% were detected in November and December and 44.5% in January and February. The hRSV epidemic started the 1st or 2nd week of October but it varied from one year to another and from one region to another. hRSV acute bronchiolitis increased from 261 cases in epidemics from 1999-2003 to 341 cases from 2004-2009. Rhinoviruses gave acute bronchiolitis in 38.4% of cases. A rate of 54.6% of viruses was detected in September and October and 38.5% in March and April. A total of 34.2% of infected infants were under 6 months of age, 37.8% between 6 months and 2 years, and 19.5% were between 2 and 5 years old. hMPV epidemics coincided with hRSV epidemics, but they accounted for one-sixth the number of cases. HMPV infected infants (74%) who were older than those infected with hRSV, and the diagnosis was bronchiolitis (59%) and pneumonia (17%). PIV infections (about 100 cases per year) included PIV3 (62.7%), PIV1 (25.3%), and PIV2 (7.3%). PIV1 infections occurred every 2 years in the fall. PIV3 infections were observed every year during the fall and winter, with peaks of infections in the spring in the years without PIV1. There were acute cases of bronchiolitis in 29.8% of PIV3 infections and 18.3% in PIV1 infections.

Acute viral bronchiolitis in children- a very common condition with few therapeutic options

Acute viral bronchiolitis remains a cause of substantial morbidity and health care costs in young infants. It is the most common lower respiratory tract condition and most common reason for admission to hospital in infants. Many respiratory viruses have been associated with acute viral bronchiolitis although respiratory syncytial virus (RSV) remains the most frequently identified virus. Most infants have a mild self limiting illness while others have more severe illness and require hospital admission and some will need ventilatory support. Differences in innate immune function in response to the respiratory viral insult as well as differences in the geometry of the airways may explain some of the variability in clinical pattern. Young age and history of prematurity remain the most important risk factors although male gender, indigenous status, exposure to tobacco smoke, poor socioeconomic factors and associated co-morbidities such as chronic lung disease and congenital heart disease increase the risks of more severe illness. Supportive therapy remains the major treatment option as no specific treatments to date have been shown to provide clinically important benefits except for inhaled hypertonic saline. Prophylaxis of high risk infants with palivizumab should be considered although the cost effectiveness is still unclear. Many questions remain regarding optimal management approaches for infants requiring hospitalisation with bronchiolitis including use of nasogastric feeding, the optimal role of supplemental oxygen, optimal use of hypertonic saline and the role of combinations of therapies, the use of heliox or modern physiotherapy approaches.

Respiratory viral infections in infants: causes, clinical symptoms, virology, and immunology

In global terms, respiratory viral infection is a major cause of morbidity and mortality. Infancy, in particular, is a time of increased disease susceptibility and severity. Early-life viral infection causes acute illness and can be associated with the development of wheezing and asthma in later life. The most commonly detected viruses are respiratory syncytial virus (RSV), rhinovirus (RV), and influenza virus. In this review we explore the complete picture from epidemiology and virology to clinical impact and immunology. Three striking aspects emerge. The first is the degree of similarity: although the infecting viruses are all different, the clinical outcome, viral evasion strategies, immune response, and long-term sequelae share many common features. The second is the interplay between the infant immune system and viral infection: the immaturity of the infant immune system alters the outcome of viral infection, but at the same time, viral infection shapes the development of the infant immune system and its future responses. Finally, both the virus and the immune response contribute to damage to the lungs and subsequent disease, and therefore, any prevention or treatment needs to address both of these factors.

High rate of viral identification and coinfections in infants with acute bronchiolitis

OBJECTIVES

To determine the viruses and risk factors associated with hospital and intensive care unit (ICU) admissions in infants with acute bronchiolitis.

INTRODUCTION

Bronchiolitis is a major cause of morbidity in infants. Widespread use of molecular-based methods has yielded new insights about its etiology, but the impact of viral etiologies on early outcomes is still unclear.

METHODS

Seventy-seven infants with bronchiolitis who were under two years of age and visited an emergency unit were included. Using molecular-based methods, samples were tested for 12 different respiratory viruses. Logistic regression models were used to identify clinical and virological variables associated with the main endpoints: hospital admission and ICU admission.

RESULTS

We identified at least one virus in 93.5% of patients, and coinfections were found in nearly 40% of patients. RSV was the most common pathogen (63.6%), followed by rhinovirus (39%). Identification of RSV was only associated with an increased risk of hospital admission in the univariate model. Younger age and enterovirus infection were associated with an increased risk of hospital admission, while atopy of a first-degree relative showed a protective effect. Prematurity was associated with an increased risk of admission to the ICU. Coinfections were not associated with worse outcomes.

CONCLUSIONS

Molecular-based methods resulted in high rates of viral identification but did not change the significant role of RSV in acute bronchiolitis. Younger age and enterovirus infection were risk factors for hospital admission, while prematurity appeared to be a significant risk factor for admission to the ICU in acute viral bronchiolitis.