Respiratory syncytial viral infection in infants with congenital heart disease

Respiratory syncytial virus infections: characteristics and treatment

In this review, we describe the history, epidemiology and clinical manifestations of infections attributed to respiratory syncytial virus (RSV) in children. At present, no cure exists for RSV infection but commonly employed palliative treatments include oxygen and inhaled β2-adrenoceptor agonists, such as salbutamol, to relieve the wheezing and increased bronchiolar smooth muscle constriction. Adrenaline (epinephrine) has been found to be superior to the selective β2-adrenoceptor agonists. Oral or inhaled corticosteroids should counteract the inflammatory response to RSV infection but their effectiveness is controversial. Inhaled ribavirin is the only licensed antiviral product approved for the treatment of RSV lower respiratory-tract infection in hospitalized children, although its use is now restricted to high-risk infants. Other treatments considered are nasopharyngeal suctioning, surfactant therapy, recombinant human deoxyribonuclease I, heliox (helium:oxygen) and inhaled nitric oxide. Prevention of infection by RSV antibodies is another strategy and, currently, palivizumab is the only safe, effective and convenient preventative treatment for RSV disease in high-risk populations of infants and young children. Its cost-effectiveness, however, has been questioned. Both live attenuated and subunit vaccines against RSV infection have been developed but so far there is no safe and effective vaccine available. Finding effective treatments and prophylactic measures remains a major challenge for the future.

Serum KL-6 levels as a biomarker of lung injury in respiratory syncytial virus bronchiolitis

To evaluate whether KL-6 concentration is a useful biomarker of the severity of respiratory syncytial virus (RSV) bronchiolitis, we determined KL-6 concentrations in patients with RSV bronchiolitis with or without chronic heart disease (CHD). We enrolled 52 patients who had been diagnosed with RSV bronchiolitis and required admission to the hospital at the Department of Pediatrics of Fukushima Medical University School of Medicine from 2004 to 2005. These patients were divided into two groups: Group 1 consisted of patients without any underlying disease, and Group 2 consisted of patients with CHD. These patients were assigned to three categories. Stage A consisted of patients without oxygen dosage, stage B of patients who required oxygen dosage, and stage C of patients required artificial respiration. We evaluated baseline characteristics, clinical features, and serum KL-6 concentration in Group 1, Group 2, and a control group (healthy infants without infection). Mean serum KL-6 concentrations in patients with RSV bronchiolitis were higher than those in the control group (471.8 +/- 236.9 and 127.1 +/- 69.1 U/ml, respectively). Mean serum KL-6 concentration was higher in Group 2 than in Group 1 (692.8 +/- 313.1 and 390.4 +/- 132.7 U/ml, respectively). Mean serum KL-6 concentrations were higher in stage C than in stages A and B, and mean serum KL-6 concentrations were higher in stage B than in stage A. These findings suggest that serum KL-6 is associated with the severity of RSV bronchiolitis and that it may be a useful biomarker for the severity of RSV bronchiolitis.

Congenital anomalies and resource utilization in neonates infected with herpes simplex virus

BACKGROUND

Neonatal herpes simplex virus (HSV) infection, while uncommon, is associated with substantial morbidity and mortality. However, there is little nationally representative data describing resource utilization.

METHODS

This retrospective cohort study was conducted using the Pediatric Health Information System, an administrative database that contains discharge diagnosis and resource utilization data from 35 free-standing children's hospitals. Patients <or=60 days of age with a primary discharge diagnosis of HSV were study eligible if they received intravenous acyclovir and were discharged between January 1, 2003 and December 31, 2005.

RESULTS

There were 406 patients with HSV. The median age was 16 days (interquartile range: 8-31 days); 52% of patients were female. Congenital heart disease, the most common congenital anomaly, occurred in 10% of patients. The median length of stay was 15 days; 21 (5%) patients died. HSV was associated with substantial resource utilization. The median hospital charge was $37,431 (interquartile range: $14,667-$74,559) per infant. The presence of congenital heart disease independently increased the hospital length of stay by 93% (adjusted LOS ratio: 1.93; 95% CI: 1.5-2.5).

CONCLUSIONS

HSV infection in neonates and young infants was associated with substantial resource utilization. The presence of an underlying congenital cardiac anomaly was associated with a significantly longer length of stay and higher hospital charges.

Severe respiratory syncytial virus (RSV) infection in infants with neuromuscular diseases and immune deficiency syndromes

Respiratory syncytial virus (RSV) is an important cause of lower respiratory tract infection (LRTI) in infants and children. There is growing evidence of severe RSV disease in infants with neuromuscular diseases and immune deficiency syndromes. Factors predisposing to a more severe course of RSV disease in neuromuscular diseases include the impaired ability to clear secretions from the airways due to ineffective cough, respiratory muscle weakness, high prevalence of gastro-oesophageal reflux and swallowing dysfunction which leads to aspiration. Similarly, pulmonary disease is a common presenting feature and complication of T-cell immunodeficiency. Infants with severe congenital and acquired immune deficiency syndromes may demonstrate prolonged viral shedding in RSV LRTI and are reported to have increased morbidity and mortality associated with RSV infection. Although not indicated in most guideline statements, palivizumab prophylaxis for these uncommon underlying conditions is under consideration by clinicians. Prospective studies are needed to determine the burden of RSV disease in these children.

Respiratory syncytial virus infection induces a reactive oxygen species-MSK1-phospho-Ser-276 RelA pathway required for cytokine expression

Respiratory syncytial virus (RSV) is a human pathogen that induces airway inflammation, at least in part, by modulating gene expression programs in airway epithelial cells. The presence of RSV replication is detected by the intracellular retinoic acid-inducible gene I (RIG-I) RNA helicase that forms a productive signaling complex with the mitochondrion-anchored MAVS protein, resulting in nuclear translocation of the NF-kappaB transcription factor. Although nuclear translocation is a prerequisite for activation of the innate inflammatory response, recent studies show that separate pathways governing RelA activation are also required for target gene expression. In this study, we examine the mechanism of RelA phosphorylation and its requirement for RSV-induced gene expression. RSV infection produced a time-dependent RelA phosphorylation on serine (Ser) residues Ser-276 and Ser-536 in parallel with enhanced reactive oxygen species (ROS) stress. Inhibition of RSV-induced ROS inhibited formation of phospho-Ser-276 RelA without affecting phospho-Ser-536 RelA formation. RSV potently induced activation of cytoplasmic mitogen- and stress-related kinase 1 (MSK1) in an ROS-dependent manner. Inhibition of MSK1 using H89 and small interfering RNA knockdown both reduced RSV-induced phospho-Ser-276 RelA formation and expression of a subset of NF-kappaB-dependent genes. Direct examination of the role of phospho-Ser-276 in target gene expression by expression of a RelA Ser-276-to-Ala site mutation in RelA(-/-) mouse embryonic fibroblasts showed that the mutation was unable to mediate RSV-induced NF-kappaB-dependent gene expression. We conclude that RSV induces RelA activation in the innate inflammatory response via a pathway separate from that controlling RelA cytoplasmic release, mediated by ROS signaling to cytoplasmic MSK1 activation and RelA Ser-276 phosphorylation.

The influence over a period of 8 years of patterns of prescribing palivizumab for patients with and without congenitally malformed hearts, and in admissions to paediatric intensive care

OBJECTIVES

To describe the pattern of prescribing for palivizumab in the Glasgow area over the period 1999 through 2007, and to compare recent prescribing to the current recommendations by the Joint Committee on Vaccination and Immunisation of the United Kingdom Department of Health. Our secondary objective was to describe admissions to paediatric intensive care in patients with respiratory syncytial virus receiving palivizumab.

SETTING

Tertiary children's hospital out-patient immunisation clinic and paediatric intensive care unit.

DESIGN

Prospective analysis of prescribing and admissions data for the period 1999 through 2007.

OUTCOME MEASURES

Number of prescriptions and admissions to the paediatric intensive care unit.

RESULTS

The number of children receiving palivizumab annually initially rose more than 5-fold, from 17 in the season of 1999 and 2000 versus 115 in 2004 and 2005, although it has declined in the past 2 years, to 63 in 2006 and 2007, following publication of the recommendations of the Joint Committee on Vaccination and Immunisation established by the United Kingdom Department of Health. There has been no significant change in demographics of patients during this period. Prior to publication of these recommendations, 35 of 44 (80%) patients with congenitally malformed hearts who received palivizumab in the season of 2005 and 2006 deviated from the current recommendations, compared to 5 of 51 (10%) who received palivizumab for non-cardiac indications. No patients who received palivizumab required admission to the paediatric intensive care unit with proven respiratory syncytial virus infection over the 8 year period.

CONCLUSIONS

The number of children receiving palivizumab initially increased significantly, although it has now fallen following implementation of national recommendations. Much prescribing, particularly for children with congenitally malformed hearts, did not fulfil current recommendations. The absence of admissions to paediatric intensive care reflects the success of targeted immunisation in our population.

Emerging genotypes of human respiratory syncytial virus subgroup A among patients in Japan

Human respiratory syncytial virus (HRSV) is a common etiological agent of acute lower respiratory tract disease in infants. We report the molecular epidemiology of HRSV in Niigata, Japan, over six successive seasons (from 2001 to 2007) and the emerging genotypes of HRSV subgroup A (HRSV-A) strains. A total of 488 HRSV samples were obtained from 1,103 screened cases in a pediatric clinic in Niigata. According to the phylogenetic analysis, among the PCR-positive samples, 338 HRSV-A strains clustered into the previously reported genotypes GA5 and GA7 and two novel genotypes, NA1 and NA2, which were genetically close to GA2 strains. One hundred fifty HRSV-B strains clustered into three genotypes, namely, GB3, SAB3, and BA, which has a 60-nucleotide insertion in the second hypervariable region of the G protein. The NA1 strains emerged first, in the 2004-2005 season, and subsequently, the NA2 strain emerged in the 2005-2006 season. Both strains caused large epidemics in the 2005-2006 and 2006-2007 seasons. The average age of children who were infected with NA2 strains was significantly higher than that of those infected with GA5 and the frequency of reinfection by NA2 was the highest among all genotypes, suggesting that this genotype possessed new antigenicity for evading past host immunity. This is the first paper to show a possible correlation between an emerging genotype, NA2, and large outbreaks of HRSV in Japan. Continuing studies to follow up the genetic changes and to clarify the mechanism of reinfection in HRSV are important steps to understand HRSV infections.

Respiratory syncytial virus prophylaxis: a survey of pediatric solid organ transplant centers

RSV can cause respiratory illness after SOT, yet preventive recommendations are lacking for this population. To ascertain current preventive practices against RSV disease in pediatric SOT candidates and recipients, a survey was developed. The survey was mailed to 108 SOT programs in the United States (liver, 42; heart, 28; lung, 11; intestinal, 25; and heart-lung, 2). Results were tabulated and analyzed using standard methods. Sixty-two percent (67/108) of surveys were completed. Forty-nine percent (33/67) of programs reported using RSV prophylaxis; palivizumab was used at 97% (32/33) of centers with 26 giving palivizumab to candidates and 27 to recipients. Prophylaxis was provided to infants aged 0-12 months by 27/29 (93%) of responding centers; 23/29 of centers extended its use to infants aged 0-24 months. Three centers gave prophylaxis to children between ages two and four yr and two centers for those over four yr. RSV prophylactic strategies, and in particular the use of palivizumab, are employed by almost 50% of responding pediatric SOT centers. Strategies varied at centers based on age and organ type. Data on RSV hospitalization and outcome are needed to refine approaches to RSV immunoprophylaxis in these high-risk patients.

Experience with the use of palivizumab together with infection control measures to prevent respiratory syncytial virus outbreaks in neonatal intensive care units

Respiratory syncytial virus (RSV) frequently causes nosocomial outbreaks in general paediatric wards and occasionally in neonatal intensive care units (NICUs). Conventional infection control measures often fail to prevent the spread of RSV, and it can cause significant morbidity especially in preterm and young infants. We report our experience in preventing an outbreak on a NICU after RSV had been detected in a premature infant. The index case was a 34-day-old premature infant who presented with clinical infection and RSV was detected in a clinical specimen. There were 11 patients in the ward at the time including the index case. The RSV-positive patient was isolated, the ward closed to admissions and infection control measures were implemented. Two patients were transferred to another hospital. Palivizumab 15 mg/kg i.m. was given to all patients and no further cases occurred. All subsequent RSV tests on nasal secretions were negative. Palivizumab combined with conventional infection control measures appeared to prevent the spread of RSV in this NICU. Strategies for the prevention of RSV outbreaks on NICUs all recommend the reinforcement of routine infection control measures. Recommendations concerning the use of palivizumab range from monthly prophylaxis to all infants at risk, to prophylaxis of selected cases only. Currently there are no guidelines for the use of palivizumab in NICUs or for the control of RSV outbreaks.

Identification and management of severe respiratory syncytial virus

PURPOSE

Identifying children at risk for severe respiratory syncytial virus (RSV) so that the most appropriate management strategies can be implemented, thereby reducing the morbidity associated with this disease, is discussed.

SUMMARY

RSV infection is associated with a variety of clinical manifestations, ranging from mild cold-like symptoms to more severe disease. The majority of infants infected with RSV develop mild upper respiratory tract disease during their initial RSV infection. However, more severe RSV disease can occur when the lower respiratory tract becomes involved, with symptoms escalating to include significant wheezing and chest-wall retractions, as well as cyanosis and tachypnea in the most severe cases. Extrapulmonary manifestations of RSV disease also have been observed, such as sepsis-like syndrome and arrhythmias. Factors that increase the risk of acquiring RSV infection have been identified, along with factors that increase the risk of severe RSV disease. The American Academy of Pediatrics (AAP) recommends that clinicians assess risk factors for severe disease when making decisions regarding evaluation and management of children with bronchiolitis. There is currently no curative treatment for RSV infection, and management primarily involves the treatment of specific symptoms. The AAP developed clinical practice guidelines to provide an evidence-based approach to the diagnosis and management of bronchiolitis in children aged one month to two years, with detailed recommendations on which therapies are appropriate for children with more severe RSV disease.

CONCLUSION

The AAP developed specific guidelines for the management of RSV bronchiolitis; however, treatment is primarily supportive and has been shown to be suboptimal in many patients. Because of the limitations associated with the management of RSV disease, prevention remains of paramount importance, especially in patients at high risk for severe disease.

Nationwide survey of palivizumab for respiratory syncytial virus prevention in Japanese children with congenital heart disease

A questionnaire study was performed to determine the current status of palivizumab prophylaxis against respiratory syncytial virus infection in Japanese children with congenital heart disease <2 years of age. Palivizumab prophylaxis decreased the respiratory syncytial virus hospitalization rate by 42.8%.

Young infants can develop protective levels of neutralizing antibody after infection with respiratory syncytial virus

Humoral immunity protects against severe respiratory syncytial virus (RSV) disease, but the range and magnitude of antibody responses in RSV-naive children after RSV infection have not been completely defined. We evaluated RSV-neutralizing antibody and immunoglobulin G responses to RSV F and G glycoproteins in 65 RSV-naive Navajo and White Mountain Apache children aged 0-24 months who were hospitalized with RSV infection. In these children, antibody responses developed against RSV F and G and the central conserved region of RSV G. Twenty-seven of 41 infants <6 months old developed reciprocal log(2) RSV neutralizing antibody titers > or =8.0, which correlate with protection of the lower respiratory tract. Multivariate analysis demonstrated that the level of preexisting neutralizing antibody at infection, not age, was the most important factor influencing this response. RSV can induce substantial neutralizing antibody responses in young infants when the titer of preexisting antibodies is low.

Prospective multicenter bronchiolitis study: predicting intensive care unit admissions

OBJECTIVES

The authors sought to identify predictors of intensive care unit (ICU) admission among children hospitalized with bronchiolitis for > or =24 hours.

METHODS

The authors conducted a prospective cohort study during two consecutive bronchiolitis seasons, 2004 through 2006, in 30 U.S. emergency departments (EDs). All included patients were aged <2 years and had a final diagnosis of bronchiolitis. Regular floor versus ICU admissions were compared.

RESULTS

Of 1,456 enrolled patients, 533 (37%) were admitted to the regular floor and 50 (3%) to the ICU. Comparing floor and ICU admissions, multivariate ED predictors of ICU admission were age <2 months (26% vs. 53%; odds ratio [OR] = 4.1; 95% confidence interval [CI] = 2.1 to 8.3), an ED visit the past week (25% vs. 40%; OR = 2.2; 95% CI = 1.1 to 4.4), moderate/severe retractions (31% vs. 48%; OR = 2.6; 95% CI = 1.3 to 5.2), and inadequate oral intake (31% vs. 53%; OR = 3.3; 95% CI = 1.6 to 7.1). Unlike previous studies, no association with male gender, socioeconomic factors, insurance status, breast-feeding, or parental asthma was found with ICU admission.

CONCLUSIONS

In this prospective multicenter ED-based study of children admitted for bronchiolitis, four independent predictors of ICU admission were identified. The authors did not confirm many putative risk factors, but cannot rule out modest associations.

Improved outcomes with home-based administration of palivizumab: results from the 2000-2004 Palivizumab Outcomes Registry

BACKGROUND

Palivizumab Outcomes Registry data collected during 4 years were examined to assess compliance and respiratory syncytial virus (RSV) hospitalization rates in high-risk children receiving palivizumab prophylaxis at home compared with an outpatient setting.

METHODS

Prospective observational registry enrolling high-risk infants who received > or = 1 dose of palivizumab throughout the 2000-2001 to 2003-2004 RSV seasons at participating U.S. pediatric sites.

RESULTS

Registry data were analyzed for compliance and RSV hospitalization outcomes in 19,548 infants receiving doses at home versus an outpatient setting. Compliance with the injection regimen was determined by comparing the number of palivizumab injections received versus the projected number of anticipated doses and by comparing infants receiving all injections within a 35-day interval. Compliance was significantly greater for infants who received palivizumab at home (n = 1226) as compared with those who received palivizumab in a clinic or office (n = 17,641), whether measured by the number of doses received (88% versus 81%, P < 0.0001) or by the timing of doses (73% versus 66%, P < 0.0001). Infants who received palivizumab at home also had fewer RSV-associated hospitalizations compared with those who received palivizumab in a clinic or office [0.4% (5/1226) versus 1.2% (207/17,641), P = 0.0139].

CONCLUSIONS

Home administration of palivizumab was associated with a significantly higher rate of compliance and lower hospitalization rate for RSV illness in high-risk infants.

Overcoming T cell-mediated immunopathology to achieve safe RSV vaccination

Respiratory syncytial virus (RSV) is the leading cause of lower respiratory tract disease in young children. Premature infants, immunocompromised individuals, and the elderly exhibit an increased risk for the development of severe disease after RSV infection. Currently, there is not a safe and effective RSV vaccine available, in part due to our incomplete understanding of how severe immunopathology was induced following RSV infection of children previously immunized with a formalin-inactivated RSV vaccine. Much of our current understanding of RSV vaccine-enhanced disease can be attributed to the establishment of multiple mouse models of RSV vaccination. Studies analyzing the RSV-specific immune response in mice have clearly demonstrated that both CD4 and CD8 memory T cells contribute to RSV-induced immunopathology. In this review we will focus our discussion on data generated from the mouse models of RSV immunization that have advanced our understanding of how virus-specific T cells mediate immunopathology and RSV vaccine-enhanced disease.

Prevention of hospitalization due to respiratory syncytial virus: results from the Palivizumab Outcomes Registry

OBJECTIVE

The Palivizumab Outcomes Registry contains data on infants and young children who received palivizumab for the prevention of respiratory syncytial virus (RSV) that causes serious lower respiratory tract illness.

STUDY DESIGN

Prospective observational registry enrolling those who received >or=1 dose of palivizumab during any RSV season (2000 to 2004) at participating US sites.

RESULT

Of 19 548 subjects enrolled, 40% were born before 32 weeks', 48% between 32 and 35 weeks' and 12% after 35 weeks' gestation. Risk factors included child-care attendance, prematurity, chronic lung disease (CLD) and congenital heart disease (CHD). The RSV hospitalization rate of palivizumab recipients was 1.3%. Gender, gestational age <32 weeks, CLD, CHD, congenital airway abnormality, severe neuromuscular disease, Medicaid insurance and >2 children in household were associated with significantly higher rates. Home-care prophylaxis with palivizumab was associated with reduced hospitalization rates.

CONCLUSION

Data on the use of palivizumab prophylaxis in primarily high-risk infants confirm low RSV hospitalization rates.

Palivizumab for the prophylaxis of respiratory syncytial virus infection

Palivizumab (Synagis®, MedImmune, Inc., USA) is a humanized monoclonal antibody that provides immunoprophylaxis against respiratory syncytial virus (RSV). RSV causes seasonal epidemics (winter or wet-season) of serious lower respiratory tract infections in young infants with subsequent increased frequency of recurrent wheezing during early childhood. Two large, double-blind, placebo-controlled trials including infants at high risk for severe RSV infection showed significant reduction of RSV-related hospitalizations: a 55% reduction in 1502 infants with prematurity and/or bronchopulmonary dysplasia and a 45% reduction in 1287 infants with hemodynamically significant congenital heart disease. Palivizumab proved to be as safe as an intramuscular injection of 15 mg/kg every 30 days for 5 months according to local epidemiology. Recent data suggest further benefits for palivizumab prophylaxis by reduction of recurrent post-RSV wheezing.

Chapter 8 Paramyxoviruses

The paramyxoviruses are a heterogeneous group of viruses causing a variety of clinical diseases in humans, animals, and birds. This chapter examines in more detail the structure and properties of the important human viruses in this group, namely measles, respiratory syncytial virus (RSV), mumps and parainfluenza viruses I-V. They are all enveloped, negative-stranded, riboviruses of helical symmetry. It is suggested that susceptible children, adolescents, and adults should be vaccinated against mumps, unless vaccination is contraindicated. Mumps vaccine can be of particular value to children approaching puberty and for adolescents and adults, especially males who have not had mumps in childhood. Ribavirin therapy may be particularly beneficial for children at risk for severe and often fatal RSV infection, such as infants with congenital heart disease. Attenuated measles vaccines have been developed empirically by selection of host range mutants, and are widely and successfully used throughout the world. Using the vaccine, some countries may soon eliminate measles as an endogenous virus but continued problems are anticipated, particularly in adults with viruses re-introduced by visitors from abroad. Basic studies on new antivirals are continuing (particularly with oligopeptides) but antiviral compounds are unlikely to have extended use in the clinic, except perhaps in tropical areas where the disease may be life threatening. However, a vaccination programme in these areas is preferable, and is an urgent need.

Prospective multicenter study of bronchiolitis: predicting safe discharges from the emergency department

OBJECTIVE

Bronchiolitis is the leading cause of hospitalization for infants. Our objective was to identify factors associated with safe discharge to home from the emergency department.

METHODS

We conducted a prospective cohort study during 2 consecutive bronchiolitis seasons, from 2004 to 2006. Thirty US emergency departments contributed data. All patients were < 2 years of age and had a final emergency department attending physician diagnosis of bronchiolitis. Using multivariate logistic regression, a low-risk model was developed with a random half of the data and then validated with the other half.

RESULTS

Of 1456 enrolled patients, 837 (57%) were discharged home from the emergency department. The following factors predicted safe discharge to home: age of > or = 2 months, no history of intubation, a history of eczema, age-specific respiratory rates (< 45 breaths per minute for 0-1.9 months, < 43 breaths per minute for 2-5.9 months, and < 40 breaths per minute for 6-23.9 months), no/mild retractions, initial oxygen saturation of > or = 94%, fewer albuterol or epinephrine treatments in the first hour, and adequate oral intake. The importance of each factor varied slightly according to age, but the comprehensive model (developed and validated for all children < 2 years of age) yielded an area under the receiver operating characteristic curve of 0.81, with a good fit of the data.

CONCLUSIONS

This large multicenter study of children presenting to the emergency department with bronchiolitis identified several factors associated with safe discharge, including cut points for respiratory rate and oxygen saturation. Although the low-risk model requires further study, we believe that it will assist clinicians evaluating children with bronchiolitis and may help reduce some unnecessary hospitalizations.

Palivizumab use in subjects with congenital heart disease: results from the 2000-2004 Palivizumab Outcomes Registry

The Palivizumab Outcomes Registry prospectively collected data on 19,548 subjects who received respiratory syncytial virus (RSV) prophylaxis with palivizumab during the 2000-2004 RSV seasons. We evaluated the characteristics of enrolled registry subjects with congenital heart disease (CHD) over the four RSV seasons and examined additional information on these subjects collected in the 2002-2004 seasons. The percentage of registry subjects with CHD increased from 4.8% (102/2116) in the first season to 11.4% (688/6050) in the last season. Across all four seasons, 1500 subjects with CHD were enrolled, 71% of whom had acyanotic CHD. The proportion with cyanotic CHD increased from 19.6% (20/102) in the 2000-2001 season to 37.5% (258/688) in the 2003-2004 season, while the proportion of all CHD in the registry more than doubled during this time. The cumulative RSV hospitalization rate was 1.9% among patients with CHD who received prophylaxis. Among subjects with cyanotic and acyanotic CHD, hospitalization rates were 2.6% and 1.6%, respectively. Prospective data collected in the Palivizumab Outcomes Registry provide the largest published dataset available on infants with CHD receiving palivizumab and show low hospitalization rates and use consistent with prelicensure clinical trial data and revised American Academy of Pediatrics guidelines.

A new assay system for evaluation of developmental immunotoxicity of chemical compounds using respiratory syncytial virus infection to offspring mice

We evaluated the effect of 6-propyl-2-thiouracil (PTU), an anti-thyroid agent, on developmental immunity using respiratory syncytial virus (RSV) infection to offspring mice as a new risk assessment for brominated flame retardants (BFRs), because some BFRs are suspected of affecting the thyroid system. Pregnant mice were exposed to PTU in drinking water from gestation day 10 to weaning on postnatal day 21. Their offspring mice were infected intranasally with RSV. Exposure of 100ppm PTU significantly increased virus titers in the lungs of RSV-infected offspring compared with the control, and the 10ppm also elevated levels of interferon-γ, a marker of pneumonia, in the bronchoalveolar lavage fluids of offspring. Histopathological analysis revealed that PTU-exposure exacerbated pneumonia in RSV-infected offspring. Thus, exacerbation of RSV infection suggested PTU-exposure of dams elicited developmental immune disorder in the offspring. The murine RSV infection model may be useful to evaluate the developmental immunotoxicity of BFRs.

[Severe bronchiolitis. Epidemiology and clinical course of 284 patients]

INTRODUCTION

Bronchiolitis is the leading cause of hospital admission and a frequent cause of pediatric intensive care unit (PICU) admission among infants during the winter months. The objective of this study was to analyze the characteristics and clinical course of patients admitted to the PICU for bronchiolitis.

PATIENTS AND METHOD

We performed a descriptive, observational study by clinical chart review of all patients admitted to the PICU for severe bronchiolitis from November 1994 to March 2006.

RESULTS

A total of 284 patients were included. Most were admitted during December and January and 74% had respiratory syncytial virus (RSV) infection. At least one risk factor for severe disease was present in 68% of the patients: the most frequent risk factor was age < 6 weeks (45%), followed by prematurity (30%). Mechanical ventilation was required in 64 of the 284 patients (24%). Mortality was 1.8% and was associated with chronic pre-existing illness (p < 0.001). The factors associated with a greater risk of mechanical ventilation and a longer PICU stay were the association of two or more risk factors (42/284; 15%), the presence of apnea (73/284; 25.7%), and images of pulmonary consolidation or atelectasis on admission chest X-ray (157/284; 55%).

CONCLUSIONS

Most patients admitted for severe bronchiolitis to the PICU are healthy infants whose principal risk factor is young age. The main predictors of severe clinical course during PICU stay are the association of two or more risk factors, the presence of apnea, and pulmonary consolidation on admission chest X-ray. Bronchiolitis-associated mortality is low and is associated with pre-existing chronic illness.

Peri-operative management of paediatric patients undergoing cardiac surgery--focus on respiratory aspects of care

Children requiring cardiac surgery present particular challenges in peri-operative respiratory management. The wide variety of conditions and operations and their varied impact on respiratory function makes dialogue with related medical staff essential. In most circumstances, cardiac performance is the main determinant of respiratory outcomes. Changing cardiologic and surgical approaches have combined to diminish the severity and frequency of pulmonary hypertensive issues and new treatment modalities are simplifying the intensive care approach. Patients with Down's syndrome and 22q11 deletion syndrome present particular issues related to anatomy, physiology and respiratory function. Certain conditions, including tetralogy of Fallot and cavopulmonary connections, present unique circumstances where respiratory management, sometimes including extubation, may assist in optimisation of cardiac performance. These and other conditions highlight the complexities of cardiopulmonary interactions. Cardiac performance remains the principal determinant of outcome after paediatric cardiac surgery and has the biggest impact on respiratory function.

Palivizumab in congenital heart disease: should international guidelines be revised?

Palivizumab has reduced the incidence of respiratory syncytial virus hospitalization in infants and children with congenital heart disease by 45%. Although the mortality rate of children with congenital heart disease hospitalized with respiratory syncytial virus infection has declined from 37% to approximately 3% over the past 3 decades, palivizumab has not been shown to improve mortality. There has been considerable controversy over the cost-effectiveness of administering palivizumab according to international guidelines, including children with congenital heart disease. In particular, the number of children that need to be treated with palivizumab to prevent one respiratory syncytial virus hospitalization increases dramatically in children > 12 months of age. As a result, the authors recommend that countries re-examine their recommendations for providing palivizumab up to age 24 months in children with congenital heart disease.

Palivizumab and the prevention of respiratory syncytial virus illness in pediatric patients with congenital heart disease

Respiratory syncytial virus (RSV) is a significant pathogen for infants and children with congenital heart disease. Non-sustained immunity and failure to develop an effective vaccine has steered RSV management toward a passive immunotherapy strategy in at-risk children. Palivizumab is a humanized murine monoclonal antibody targeting the RSV envelope F glycoprotein. In a Phase III clinical trial palivizumab significantly reduced RSV hospitalization in children with significant congenital heart disease and was proven to be safe. Palivizumab is one of the first monoclonal antibodies to significantly impact a pediatric disease.

Down syndrome: a novel risk factor for respiratory syncytial virus bronchiolitis--a prospective birth-cohort study

OBJECTIVES

Respiratory syncytial virus is the single-most important cause of lower respiratory tract infections in children. Preterm birth and congenital heart disease are known risk factors for severe respiratory syncytial virus infections. Although Down syndrome is associated with a high risk of respiratory tract infections, little is known about the incidence of respiratory syncytial virus infections in this group. The aim of our study was to determine the incidence of respiratory syncytial virus lower respiratory tract infection-associated hospitalization among children with Down syndrome.

PATIENTS AND METHODS

We performed a retrospective observational study and a prospective nationwide birth-cohort study of children with Down syndrome. The retrospective cohort comprised 176 children with Down syndrome. A birth cohort of 219 children with Down syndrome was prospectively followed until 2 years of age. All 276 siblings of the birth cohort were used as controls.

RESULTS

Of the 395 patients with Down syndrome, 180 (45.6%) had a known risk factor for severe respiratory syncytial virus infections; 39 (9.9%) of these were hospitalized for respiratory syncytial virus lower respiratory tract infections. Two control children (0.7%) versus 9 term children with Down syndrome without congenital heart disease (7.6%) were hospitalized for respiratory syncytial virus lower respiratory tract infections. The median duration of hospitalization was 10 days; mechanical ventilation was required for 5 children (12.8%).

CONCLUSIONS

This is the first study, to our knowledge, to demonstrate that Down syndrome is a novel independent risk factor for severe respiratory syncytial virus lower respiratory tract infections. These findings should prompt studies to investigate possible mechanisms that underlie severe respiratory syncytial virus lower respiratory tract infections in children with Down syndrome. The effect of respiratory syncytial virus prophylaxis in this specific population needs to be established.

A population-based study relevant to seasonal variations in causes of death in children undergoing surgery for congenital cardiac malformations

AIMS

Our objectives were, first, to study seasonal distribution of perioperative deaths within 30 days after surgery, and late death, in children undergoing surgery for congenitally malformed hearts, and second, to study the causes of late death.

METHODS

We analysed a retrospective cohort of 1,753 children with congenital cardiac malformations born and undergoing surgery in the period from 1990 through 2002 with a special focus on the causes of late death. The data was obtained from the registry of congenital cardiac malformations at Rikshospitalet, Oslo, and the Norwegian Medical Birth Registry. The mean follow-up from birth was 8.1 years, with a range from zero to 15.2 years.

RESULTS

During the period of follow-up, 204 (11.6%) of the children died having undergone previous surgery. Of these 124 (7.1%) died in the perioperative period, and 80 (4.5%) were late deaths. There were 56 late deaths during the 6 coldest months, compared with 24 during the 6 warmest months (p < 0.01). There was no significant seasonal variation in perioperative deaths. Respiratory infection was the most common cause of late death, and occurred in 25 children, of whom 24 died during the 6 coldest months. Of the 8 sudden late deaths, 7 occurred during the 6 coldest months. There was no seasonal variation for the other causes of death.

CONCLUSIONS

In children undergoing surgery for congenital cardiac malformations in Norway, there is a seasonal variation in late death, with a higher proportion occurring in the coldest months. Death related to respiratory infections predominantly occurs in the winter season, and is the overall most common cause of late death.

Respiratory infection in congenital cardiac disease. Hospitalizations in young children in Spain during 2004 and 2005: the CIVIC Epidemiologic Study

OBJECTIVES

To evaluate the rate of hospitalization for acute respiratory tract infection in children less than 24 months with haemodynamically significant congenital cardiac disease, and to describe associated risk factors, preventive measures, aetiology, and clinical course.

MATERIALS AND METHODS

We followed 760 subjects from October 2004 through April 2005 in an epidemiological, multicentric, observational, follow-up, prospective study involving 53 Spanish hospitals.

RESULTS

Of our cohort, 79 patients (10.4%, 95% CI: 8.2%-12.6%) required a total of 105 admissions to hospital related to respiratory infections. The incidence rate was 21.4 new admissions per 1000 patients-months. Significant associated risk factors for hospitalization included, with odds ratios and 95% confidence intervals shown in parentheses: 22q11 deletion (8.2, 2.5-26.3), weight below the 10th centile (5.2, 1.6-17.4), previous respiratory disease (4.5, 2.3-8.6), incomplete immunoprophylaxis against respiratory syncytial virus (2.2, 1.2-3.9), trisomy 21 (2.1, 1.1-4.2), cardiopulmonary bypass (2.0, 1.1-3.4), and siblings aged less than 11 years old (1.7, 1.1-2.9). Bronchiolitis (51.4%), upper respiratory tract infections (25.7%), and pneumonia (20%) were the main diagnoses. An infectious agent was found in 37 cases (35.2%): respiratory syncytial virus in 25, Streptococcus pneumoniae in 5, and Haemophilus influenzae in 4. The odds ratio for hospitalization due to infection by the respiratory syncytial virus increases by 3.05 (95% CI: 2.14 to 4.35) in patients with incomplete prophylaxis. The median length of hospitalization was 7 days. In 18 patients (17.1%), the clinical course of respiratory infection was complicated and 2 died.

CONCLUSIONS

Hospital admissions for respiratory infection in young children with haemodynamically significant congenital cardiac disease are mainly associated with non-cardiac conditions, which may be genetic, malnutrition, or respiratory, and to cardiopulmonary bypass. Respiratory syncytial virus was the most commonly identified infectious agent. Incomplete immunoprophylaxis against the virus increased the risk of hospitalization.

Immunization strategies for the prevention of pneumovirus infections

Pneumoviruses, which are viruses of the family Paramyxoviridae, subfamily Pneumovirinae, are pathogens that infect the respiratory tract of their host species. The human pneumovirus pathogen, human respiratory syncytial virus (RSV), has counterparts that infect cows (bovine RSV), sheep (ovine RSV), goats (caprine RSV) and rodents (pneumonia virus of mice). Each pneumovirus is host specific and results in a spectrum of disease, ranging from mild upper-respiratory illness to severe bronchiolitis and pneumonia with significant morbidity and mortality. Given the public health burden caused by human RSV and the concomitant agricultural impact of bovine RSV, these two viruses are considered as prime targets for the development of safe and effective vaccines. In this review, we describe the strategies used to develop vaccines against human and bovine RSV and introduce the pneumonia virus mouse model as a novel and invaluable tool for preclinical studies and new vaccine strategies.

Respiratory syncytial virus infection and recurrent wheeze/asthma in children under five years: an epidemiological survey

AIM

To determine the rates of respiratory syncytial virus (RSV) infection in children under 5 years of age with recurrent wheeze or asthma and compare their clinical presentation, course and outcome with asthmatic children of the same age who did not have RSV.

METHODS

Children were recruited prospectively from the emergency department of the Royal Children's Hospital, Melbourne during peak RSV season in 1998. Information was collected regarding past and current asthma presentations, a nasopharyngeal asprirate was taken for viral isolation and all children were reviewed by telephone 1 week following presentation.

RESULTS

73 children were included with a median age of 28 months. RSV was isolated from 33 (45%) of children, one child had adenovirus and in the remainder no virus was isolated. Children less than 12 months were more likely to have RSV (70%). RSV-positive children had a longer duration of illness prior to hospital presentation than RSV-negative children but were not more likely to be admitted or to have a longer duration of ongoing symptoms.

CONCLUSION

A high rate of RSV infection was demonstrated in young children with recurrent wheeze or asthma during the RSV season. This information has important implications for the control of nosocomial infection with RSV (i.e. isolation of patients) and in targeting another group to be included for RSV vaccine development.

In vitro and in vivo fitness of respiratory syncytial virus monoclonal antibody escape mutants

Respiratory syncytial virus (RSV) is the only infectious disease for which a monoclonal antibody (MAb) is used in humans. Palivizumab (PZ) is a humanized murine MAb to the F protein of RSV. PZ-resistant viruses appear after in vitro and in vivo growth of RSV in the presence of PZ. Fitness for replication could be a determinant of the likelihood of dissemination of resistant viruses. We assessed the fitness of two PZ-resistant viruses (F212 and MP4). F212 grew less well in cell culture than the parent A2 virus and was predicted to be less fit than A2. Equal amounts of F212 and A2 were mixed and passaged in cell culture. F212 disappeared from the viral population, indicating it was less fit than the A2 virus. The MP4 virus grew as well as A2 in culture and in cotton rats. A2/MP4 virus input ratios of 1:1, 10:1, 100:1, and 1,000:1 were compared in competitive replication. For all input ratios except 1,000:1, the MP4 virus became dominant, supplanting the A2 virus. The MP4 virus also dominated the A2 virus during growth in cotton rats. Thus, the mutant MP4 virus was more fit than A2 virus in both in vitro and in vivo competitive replication. Whether this fitness difference was due to the identified nucleotide substitutions in the F gene or to mutations elsewhere in the genome is unknown. Understanding the mechanisms by which mutant virus fitness increased or decreased could prove useful for consideration in attenuated vaccine design efforts.

Atopic disposition, wheezing, and subsequent respiratory syncytial virus hospitalization in Danish children younger than 18 months: a nested case-control study

OBJECTIVES

This study examined whether atopic disposition, wheezing, and atopic disorders increased the risk of hospitalizations because of respiratory syncytial virus in children between birth and 18 months of age.

PATIENTS AND METHODS

Relative risks for respiratory syncytial virus hospitalization were studied in a nested 1:5 case-control design using exposure information obtained from interviews with mothers of 2564 case and 12,816 control children who had been followed prospectively from birth and until 18 months of age as participants in the Danish National Birth Cohort. Information on the children's ages at respiratory syncytial virus hospitalization, presentation of infrequent wheezing, recurrent wheezing, and atopic dermatitis were used to study these associations chronologically.

RESULTS

The adjusted relative risk of respiratory syncytial virus hospitalization in the offspring was 1.11 for maternal atopic dermatitis, 1.72 for maternal asthma, and 1.23 for paternal asthma. Atopic dermatitis in the child was associated with an increased risk of subsequent respiratory syncytial virus hospitalization among infants <6 months of age. Infrequent wheezing was associated with a relative risk of subsequent respiratory syncytial virus hospitalization of 2.98 and recurrent wheezing with a relative risk of 5.90. These associations were present also if infants with medical risk factors were excluded from the analysis.

CONCLUSIONS

Asthmatic disposition and wheezing were strong determinants of subsequent respiratory syncytial virus hospitalization in Danish children <18 months of age.

Place de la ventilation non invasive nasale dans la prise en charge des broncho-alvéolites sévères

OBJECTIVE

Usefulness of nasal continuous positive airway pressure (NCPAP) in severe acute bronchiolitis has been checked. The objective of this descriptive study was to evaluate the feasibility, safety and risk factors of NCPAP failure.

POPULATION AND METHODS

One hundred and forty-five infants were hospitalised in our intensive care unit during the 2 last epidemics (2003-2004, 2004-2005). Among them, 121 needed a respiratory support, either invasive ventilation (N=68) or NCPAP (N=53).

RESULTS

General characteristics were similar during the 2 periods. Percentage of NCPAP failure, defined by tracheal intubation requirement during the stay in paediatric intensive care unit, was quite similar during the 2 periods (25%), but number of NCPAP increased twofold. Whatever the evolution was in the NCPAP group, we observed a significant decrease in respiratory rate (60+/-16 vs 47.5+/-13.7 cycle/min., P<0.001) and PaCO2 (64.3+/-13.8 vs 52.6+/-11.7 mmHg, P=0.001) during NCPAP. Only PRISM calculated at day 1 and initial reduction of PaCO2 were predictive of NCPAP failure. Percentage of ventilator associated pneumonia was similar (22%) between the invasive ventilation group and infants who where intubated because of failure of NCPAP. Duration of respiratory support and stay were reduced in the NCPAP group (P<0.002).

CONCLUSION

NCPAP appears to be a safe alternative to immediate intubation in infants with severe bronchiolitis.

Diagnosis and management of bronchiolitis

Bronchiolitis is a disorder most commonly caused in infants by viral lower respiratory tract infection. It is the most common lower respiratory infection in this age group. It is characterized by acute inflammation, edema, and necrosis of epithelial cells lining small airways, increased mucus production, and bronchospasm. The American Academy of Pediatrics convened a committee composed of primary care physicians and specialists in the fields of pulmonology, infectious disease, emergency medicine, epidemiology, and medical informatics. The committee partnered with the Agency for Healthcare Research and Quality and the RTI International-University of North Carolina Evidence-Based Practice Center to develop a comprehensive review of the evidence-based literature related to the diagnosis, management, and prevention of bronchiolitis. The resulting evidence report and other sources of data were used to formulate clinical practice guideline recommendations. This guideline addresses the diagnosis of bronchiolitis as well as various therapeutic interventions including bronchodilators, corticosteroids, antiviral and antibacterial agents, hydration, chest physiotherapy, and oxygen. Recommendations are made for prevention of respiratory syncytial virus infection with palivizumab and the control of nosocomial spread of infection. Decisions were made on the basis of a systematic grading of the quality of evidence and strength of recommendation. The clinical practice guideline underwent comprehensive peer review before it was approved by the American Academy of Pediatrics. This clinical practice guideline is not intended as a sole source of guidance in the management of children with bronchiolitis. Rather, it is intended to assist clinicians in decision-making. It is not intended to replace clinical judgment or establish a protocol for the care of all children with this condition. These recommendations may not provide the only appropriate approach to the management of children with bronchiolitis.

The current state of infection with respiratory syncytial virus in the setting of congenital cardiac malformations

A long with prematurity and chronic lung disease, the presence of congenital cardiac disease in infants and young children is a significant risk for the clinical consequences of an illness produced by infection with the respiratory syncytial virus.1In this review, we present a current understanding of such illnesses, their prevention, and their treatment.

Sharing features of uncommon respiratory syncytial virus complications in infants

We describe 4 nonconsecutive cases of infants admitted to Catholic University pediatric intensive care unit (PICU) because of complicated respiratory syncytial virus (RSV) infection during winter RSV outbreaks from the year 2000 to the year 2003. A hyponatremic epileptic status (as in the first case) has been reported by several authors as a rare RSV complication, potentially leading to death. The second infant developed a serious pulmonary edema after a subglottic obstruction (croup) associated with RSV infection. The remaining 2 infants developed a pneumothorax and subcutaneous emphysema while breathing spontaneously during an RSV bronchiolitis. In all infants, a full recovery and PICU discharge was achieved despite the need for mechanical ventilation in cases 1 and 2. Increased intrapleural negative pressure or its combination with hypoxia/hypercapnia has been suggested as the common factor possibly joining these different clinical pictures.

Peroxisome proliferator-activated receptor-γ agonists inhibit the replication of respiratory syncytial virus (RSV) in human lung epithelial cells

We have previously shown that peroxisome proliferator-activated receptor-gamma (PPARgamma) agonists inhibited the inflammatory response of RSV-infected human lung epithelial cells. In this study, we supply evidence that specific PPARgamma agonists (15d-PGJ2, ciglitazone, troglitazone, Fmoc-Leu) efficiently blocked the RSV-induced cytotoxicity and development of syncytia in tissue culture (A549, HEp-2). All PPARgamma agonists under study markedly inhibited the cell surface expression of the viral G and F protein on RSV-infected A549 cells. This was paralleled by a reduced cellular amount of N protein-encoding mRNA determined by real-time RT-PCR. Concomitantly, a reduced release of infectious progeny virus into the cell supernatants of human lung epithelial cells (A549, normal human bronchial epithelial cells (NHBE)) was observed. Similar results were obtained regardless whether PPARgamma agonists were added prior to RSV infection or thereafter, suggesting that the agonists inhibited viral gene expression and not the primary adhesion or fusion process.

Risk factors for hospitalization due to respiratory syncytial virus infection among infants in the Basque Country, Spain

This study analysed the role of several risk factors for hospitalization due to community-acquired, respiratory syncytial virus (RSV) infection. The risk factors detected in infants hospitalized for RSV infection in the first 24 months of life were compared with those in the general infant population in our region. There were 361 episodes of hospitalization in 357 infants. Eighty per cent of the infants did not present underlying conditions for severe RSV infection and only 10 (3%) were candidates for palivizumab prophylaxis. In multivariate analysis, birthweight of <2500 g was independently associated with hospitalization for RSV infection and was the most commonly detected medical risk factor. Other risk factors were maternal age at delivery <25 years, birth in the second half of the year, prematurity, suburban residence and congenital heart disease. In conclusion, together with well-known risk factors, we found that low birthweight was an independent factor for severe RSV infection.

Viral pneumonia in children

Viral pneumonia causes a heavy burden on our society. In the United States, more than one million cases of pneumonias afflict children under the age of 5 years, costing hundreds of millions of dollars annually. The majority of these infections are caused by a handful of common viruses. Knowledge of the epidemiology of these viruses combined with new rapid diagnostic techniques will provide faster and more, reliable diagnoses in the future. Although the basic clinical epidemiology of these viruses has been carefully investigated over the last 30 years, new molecular techniques are greatly expanding our understanding of these agents and the diseases they cause. Antigenic and genetic variations are being discovered in many viruses previously thought to be homogeneous. The exact roles and the biological significance of these variations are just beginning to be explored, but already evidence of differences in pathogenicity and immunogenicity has been found in many of these substrains. All of this information clearly will impact the development of future vaccines and antiviral drugs. Effective drugs exist for prophylaxis against influenza A and respiratory syncytial virus, and specific therapy exists for influenza A. Ribarivin is approved for use in respiratory synctial virus infections, and it alone or in combination with other agents (eg, IGIV) may be effective in immunocompromised patients, either in preventing the development of pneumonia or in decreasing morbidity and mortality. Many new antiviral agents are being tested and developed, and several are in clinical trials.

High incidence of pulmonary bacterial co-infection in children with severe respiratory syncytial virus (RSV) bronchiolitis

BACKGROUND

Respiratory syncytial virus (RSV) is the most common cause of viral lower respiratory tract infections (LRTI). Viral LRTI is a risk factor for bacterial superinfection, having an escalating incidence with increasing severity of respiratory illness. A study was undertaken to determine the incidence of pulmonary bacterial co-infection in infants and children with severe RSV bronchiolitis, using paediatric intensive care unit (PICU) admission as a surrogate marker of severity, and to study the impact of the co-infection on morbidity and mortality.

METHODS

A prospective microbiological analysis was made of lower airways secretions on all RSV positive bronchiolitis patients on admission to the PICU during three consecutive RSV seasons.

RESULTS

One hundred and sixty five children (median age 1.6 months, IQR 0.5-4.6) admitted to the PICU with RSV bronchiolitis were enrolled in the study. Seventy (42.4%) had lower airway secretions positive for bacteria: 36 (21.8%) were co-infected and 34 (20.6%) had low bacterial growth/possible co-infection. All were mechanically ventilated (median 5.0 days, IQR 3.0-7.3). Those with bacterial co-infection required ventilatory support for longer than those with only RSV (p<0.01). White cell count, neutrophil count, and C-reactive protein did not differentiate between the groups. Seventy four children (45%) received antibiotics prior to intubation. Sex, co-morbidity, origin, prior antibiotics, time on preceding antibiotics, admission oxygen, and ventilation index were not predictive of positive bacterial cultures. There were 12 deaths (6.6%), five of which were related to RSV.

CONCLUSIONS

Up to 40% of children with severe RSV bronchiolitis requiring admission to the PICU were infected with bacteria in their lower airways and were at increased risk for bacterial pneumonia.

Effect of altitude on hospitalizations for respiratory syncytial virus infection

OBJECTIVE

Respiratory syncytial virus (RSV) infection is the foremost cause of serious lower respiratory tract infection in young children and infants. Because higher rates of hospitalization for bronchiolitis and pneumonia have been noted in high-altitude regions, we hypothesized that physiologic responses to altitude would predispose children to more severe illness from RSV infection. This study examined the effect of residential altitude on hospitalizations for RSV infection in Colorado from 1998 through 2002.

METHODS

A geographic information system was used to assemble data for altitude and demographic variables by zip code-tabulation areas. Data then were linked with hospital discharge data for RSV infections. Poisson regression models were developed to explore correlations between hospitalization rates and residential altitude, after adjustment for socioeconomic differences in the underlying population.

RESULTS

RSV-associated hospitalizations averaged 15.9 per 1000 infants who were younger than 1 year and 1.8 per 1000 children who were 1 to 4 years of age per season. A multivariate analysis suggested that the rate of hospitalization for RSV-specific International Classification of Diseases, Ninth Revision, Clinical Modification codes increased 25% among infants who were younger than 1 year and 53% among children who were 1 to 4 years of age for every 1000-m increase in altitude. The risk for RSV-associated hospitalization was highest at elevations above 2500 m.

CONCLUSIONS

High altitude above 2500 m is a modest predictor for RSV-associated hospitalization. Practitioners in these regions should consider additional efforts to educate parents about RSV infection and its prevention and the importance of early treatment.