Prevalence of respiratory syncytial virus infection in Italian infants hospitalized for acute lower respiratory tract infections, and association between respiratory syncytial virus infection risk factors and disease severity

Respiratory outcomes, utilization and costs 12 months following a respiratory syncytial virus diagnosis among commercially insured late-preterm infants

OBJECTIVES

To determine, among a commercially-insured population of late-preterm infants, utilization of healthcare resources and costs during the 1 year following a diagnosis of respiratory syncytial virus lower respiratory infection (RSV LRI).

METHODS

Administrative claims for non-capitated, commercially-insured infants <1 year old were used to identify infants diagnosed with RSV LRI and unspecified bronchiolitis/pneumonia (UBP). Infants were stratified by the setting of diagnosis. Infants without evidence of RSV LRI or UBP were selected as a comparison group. Economic and clinical outcomes were analyzed descriptively using propensity score weighting and logged ordinary least squares models were used to examine the relationship between RSV and costs (adjusted to 2006 USD) incurred within 1 year of RSV LRI.

RESULTS

The majority of infants were 3 months or older at the time of RSV LRI or UBP diagnosis. The rate of wheezing was significantly greater for infants in the RSV LRI and UBP cohorts relative to the comparison group (p < 0.001). Infantile asthma rates were 6-9 times higher among RSV LRI and UBP infants than the comparison group. RSV LRI and UBP infants also had significantly more emergency department visits and outpatient visits than the comparison group. The marginal healthcare costs were significantly higher for RSV LRI inpatients ($24,027) and outpatients ($2703) infants than for the comparison group (all p < 0.001).

CONCLUSION

Commercially insured late-preterm infants with RSV infection are at high risk for recurrent wheezing and infantile asthma during the 1-year period after the initial episode and impose a significant economic burden to the healthcare system.

Prevention of serious respiratory syncytial virus-related illness. I: Disease pathogenesis and early attempts at prevention

Respiratory syncytial virus (RSV) was first described 160 years ago but was not officially recognized as a cause of serious illness in children until the late 1950s. It has been estimated that virtually all children have had at least one RSV infection by their second birthday. RSV is responsible for annual disease outbreaks, usually during a defined winter seasonal period that can vary by community and year. RSV is recognized as the leading cause of hospitalization among young children worldwide. Infants of young chronologic age and children with predisposing factors, such as premature birth, pulmonary disease, or congenital heart disease, are most susceptible to serious illness. Unlike other viruses, immunity to RSV infection is incomplete and short lived, and reinfection is common throughout life. Initial attempts to develop a vaccine in the 1960s met with unexpected and tragic results; many children vaccinated with a formalin-inactivated wild-type virus developed serious pulmonary disease upon subsequent natural infection. Numerous other vaccine technologies have since been studied, including vectored approaches, virus-like particles, DNA vaccines, and live attenuated virus vaccine. As of early 2010, only two companies or institutions had RSV vaccine candidates in early clinical trials, and no vaccine is likely to be licensed for marketing in the immediate future.

Children, parents and Respiratory Syncytial Virus in Palermo, Italy: prevention is primary

A study was conducted to describe the characteristics of the Respiratory Syncytial Virus (RSV) infection cases occurring in the season 2006-7 in Palermo, Italy, and to evaluate the parents' knowledge and behaviours concerning prevention and control of acute respiratory infections (ARIs). All children aged between 0 and 2 years, admitted for a lower respiratory tract infection (LRTI) between October 2006 and May 2007, were enrolled in the study. Data were collected about demographic and household characteristics. Furthermore, their parents were asked to compile a structured questionnaire on transmission, prevention and management of ARIs in children. A total of 198 children with a diagnosis of LRTI were enrolled. Ninety-eight (62.0%) of 157 were positive for RSV. Parents were generally aware of transmission of ARIs through sneezing and/or coughing, but less through contaminated objects or hands. Nationality, age and education level of parents and also the age of the patients proved to be associated with some self-reported knowledge and behaviours. Only 24 (12.3%) of the 195 respondents had received advice from GPs or paediatricians about good hygiene practices. It seems essential to implement public health interventions promoting behavioural changes aimed at the primary prevention of ARIs at the community level.

Prevalence of respiratory syncytial virus (RSV) risk factors and cost implications of immunoprophylaxis to infants 32 to 35 weeks gestation for health plans in the United States

BACKGROUND

During the period of this study, the American Academy of Pediatrics (AAP) 2006 guidelines recommended respiratory syncytial virus (RSV) prophylaxis for infants 32 to 35 weeks gestation age (wGA) with two or more of five risk factors (RFs). New recommendations have recently been published in 2009. The cost implications of expanding this list of RFs to include other evidence-based RFs like passive smoke exposure (PSE), crowded living conditions (CLCs), and young chronological age (YCA) are unclear.

METHODS

We estimated the prevalence of RSV RFs in a US sample of infants 32 to 35 wGA referred for prophylaxis from nine specialty pharmacy providers during the 2007-2008 season. We estimated the percent eligible for RSV prophylaxis under various potential RF coverage policies. Using a budget impact model, we calculated the per-member-per-month (PMPM) cost for each policy in 2007 USD for a hypothetical one million member plan.

RESULTS

Infants 32 to 35 wGA represented 0.08% of the plan. Approximately 20.2% of these infants met at least two or more of five AAP RFs. Expanding this list to include one additional RF of PSE, CLC, or YCA increased the percent of infants potentially prophylaxed to 29.9%, 23.9%, and 47%, respectively. Adding all three RFs to the list (two or more of eight) increased the percent of infants potentially prophylaxed to 55.6%, and increased payer costs by 9 cents PMPM.

CONCLUSION

Expanding the AAP RF criteria to include PSE, CLC, and YCA would identify more 32 to 35 wGA infants at high risk for severe RSV disease at an acceptable budget impact.

Secondhand smoke inhibits both Cl- and K+ conductances in normal human bronchial epithelial cells

Secondhand smoke (SHS) exposure is an independent risk factor for asthma, rhinosinusitis, and more severe respiratory tract infections in children and adults. Impaired mucociliary clearance with subsequent mucus retention contributes to the pathophysiology of each of these diseases, suggesting that altered epithelial salt and water transport may play an etiological role. To test the hypothesis that SHS would alter epithelial ion transport, we designed a system for in vitro exposure of mature, well-differentiated human bronchial epithelial cells to SHS. We show that SHS exposure inhibits cAMP-stimulated, bumetanide-sensitive anion secretion by 25 to 40% in a time-dependent fashion in these cells. Increasing the amount of carbon monoxide to 100 ppm from 5 ppm did not increase the amount of inhibition, and filtering SHS reduced inhibition significantly. It was determined that SHS inhibited cAMP-dependent apical membrane chloride conductance by 25% and Ba²⁺-sensitive basolateral membrane potassium conductance by 50%. These data confirm previous findings that cigarette smoke inhibits chloride secretion in a novel model of smoke exposure designed to mimic SHS exposure. They also extend previous findings to demonstrate an effect on basolateral K⁺ conductance. Therefore, pharmacological agents that increase either apical membrane chloride conductance or basolateral membrane potassium conductance might be of therapeutic benefit in patients with diseases related to SHS exposure.

Preventing RSV bronchiolitis in vulnerable infants: the role of palivizumab

As the vast majority of infants tolerate infection with the respiratory syncytial virus [RSV] well and can be managed in the home, most should not be considered for RSV prophylaxis with palivizumab. However, there exists a subset of vulnerable infants in whom the consequences of RSV infection are greater, with an increased likelihood of intensive care admission and mechanical ventilation. These include children born extremely preterm with chronic neonatal lung disease and infants with haemodynamically significant cardiac disease in whom there exists level II evidence to suggest that palivizumab may reduce their risk of acquiring RSV by approximately 50%. The use of palivizumab varies considerably across the world, based largely on economic considerations. This article reviews the strategies developed to fight RSV infection, the evidence for the use of palivizumab and suggests a reasonable approach clinically and economically to the use of palivizumab, proposing its use selectively in the most vulnerable infants during the first six months of life.

Environmental tobacco smoke (ETS) and respiratory health in children

Environmental tobacco smoke (ETS) is a major risk factor for poor lung health in children. Although parental smoking is the commonest source of ETS exposure to children, they are also exposed to ETS in schools, restaurants, public places and public transport vehicles. Apart from containing thousands of chemicals, the particle size in the ETS is much smaller than the main stream smoke, and therefore has a greater penetrability in the airways of children. Exposure to ETS has been shown to be associated with increased prevalence of upper respiratory tract infections, wheeze, asthma and lower respiratory tract infections. Even developing fetuses are exposed to ETS via the umbilical cord blood if the mother is exposed to tobacco smoke. The placenta also does not offer any barrier to the penetration of ETS into the fetus. The immune system in these babies is more deviated toward the allergic and asthmatic inflammatory phenotype and therefore makes them more prone to develop asthma later in life. An increased awareness of the harmful effects of ETS on children's health is warranted.

Epidemiological assessment of Respiratory Syncytial Virus infection in hospitalized infants, during the season 2005-2006 in Palermo, Italy

Objectives

Respiratory Syncytial Virus (RSV) is the leading cause of hospitalization for lower respiratory tract infections (LRTI) in young children worldwide.

We evaluate the epidemiological and clinical patterns of RSV infection in infants hospitalized for LRTI in in Palermo, South Italy, Sicily.

Methods

We collected the demographic details of infants hospitalized to G. Di Cristina Children's Hospital in Palermo for LRTI between November 2005 and May 2006. We also included all cases occurred in newborns hospitalized in the Neonatal Intensive Care Unit (NICU) Of Palermo.

Results

During the studied period, 335/705 hospitalized infants for LRTI were enrolled in the study. The trend of hospitalization started in late winter and lasting until May 2006 with an epidemic peak in spring. 178/335 infants tested for viral infection showed RSV disease. Three cases occurred in preterm newborns hospitalized from birth in NICU. The likelihood to be RSV+, rather than RSV negative (RSV-) was higher for infants < 6 months and lower for infants with history of breast feeding (P < 0.05). RSV infection was associated with a higher likelihood to be admitted to intensive care unit and to a longer hospitalization and oxygen therapy.

Conclusion

The study shows that, in Sicily, RSV is an important cause of LRTI in infants. The seasonal distribution shows that both LRTI and RSV infections peak in late spring, in contrast to Northern Italy. Our data could help to define the regional appropriate start of prophylactic interventions.

Descriptive epidemiological features of bronchiolitis in a population-based cohort

OBJECTIVE

The goal was to investigate the epidemiological features of incident bronchiolitis by using a population-based infant cohort.

METHODS

Outpatient and inpatient health records were used to identify incident bronchiolitis cases among 93,058 singleton infants born in the Georgia Air Basin between 1999 and 2002. Additional health-related databases were linked to provide data on sociodemographic variables, maternal characteristics, and birth outcome measures.

RESULTS

From 1999 to 2002, bronchiolitis accounted for 12,474 incident health care encounters (inpatient or outpatient contacts) during the first year of life (134.2 cases per 1000 person-years). A total of 1588 hospitalized bronchiolitis cases were identified (17.1 cases per 1000 person-years). Adjusted Cox proportional-hazard analyses for both case definitions indicated an increased risk of incident bronchiolitis in the first year of life (follow-up period: 2-12 months) for boys, infants of First Nations status, infants with older siblings, and infants living in neighborhoods with smaller proportions of maternal postsecondary education. The risk also was elevated for infants born to young mothers (<20 years of age) or mothers who did not initiate breastfeeding in the hospital. Infants with low (1500-2400 g) or very low (<1500 g) birth weight and those with congenital anomalies also had increased risk. Maternal smoking during pregnancy increased the risk of hospitalized bronchiolitis.

CONCLUSIONS

This population-based study of the epidemiological features of bronchiolitis provides evidence for intervening with high-risk infants and their families. Clinical and public health interventions are recommended for the modifiable risk factors of maternal breastfeeding and smoking and for modification of vulnerable environments where possible (eg, limiting exposure to other young children), during high-risk periods such as the first few months of life or the winter season.

Host, family and community proxies for infections potentially associated with leukaemia

Three hypotheses have proposed the involvement of infections in the aetiology of childhood leukaemia, suggesting either a specific leukaemogenic infection or a series of common infections that lead to a dysregulation of the immune system. Much of the evidence for the link with infections has been based on epidemiological observations, often using proxy measures of infection. Proxy measures include population mixing, parental occupation, age distribution of incidence, spatial and space-time clustering of cases, birth order and day care during infancy. This paper discusses the proxies used and examines to what extent a commonly used proxy measure, birth order, is a fair representation of either specific infections or general infectious load. It is clear that although leukaemia, and other diseases, may be linked with infections, one needs to (1) measure specific and general infections with more accuracy and (2) understand how proxy measures relate to real infections in the population.

Incidence and risk factors of lower respiratory tract illnesses during infancy in a Mediterranean birth cohort

Aim: To investigate the incidence rate, viral respiratory agents and determinants of lower respiratory tract illnesses (LRTIs) in infants younger than 1 year.

Methods: A total of 487 infants were recruited at birth for the Asthma Multicenter Infant Cohort Study in Barcelona (Spain). Cases of LRTIs were ascertained through an active register including a home visit and viral test in nasal lavage specimens during the first year of life. Cotinine in cord blood, household aeroallergens, indoor NO₂ and maternal and neonatal IgE were measured. Other maternal and infants' characteristics were obtained from structured questionnaires.

Results: The incidence rate of at least one LRTI was 38.7 infants per 100 persons‐years. The most frequently isolated viral agent was respiratory syncytial virus (44.7%). The risk of LRTIs was higher in infants with a maternal history of asthma and in those with siblings (OR = 2.4; 95% CI: 0.98–6.08 and OR = 1.8; 95% CI: 1.04–3.21, respectively). The risk of LRTIs was lower in infants who were breast fed for more than 12 weeks (OR = 0.26; 95% CI: 0.26–0.86) and in those from a low socioeconomic class (OR = 0.16; 95% CI: 0.06–0.42).

Conclusion: Viral LRTIs are frequent in infants younger than 1 year of age and there is an inter‐relationship between maternal asthma, siblings, breast feeding and socioeconomic status.

Respiratory syncytial virus infections in hospitalized infants: association between viral load, virus subgroup, and disease severity

The relationships between host factors, virus strain, viral load, and illness severity in respiratory syncytial virus (RSV)-induced bronchiolitis are poorly defined. These relationships were evaluated prospectively in 81 previously healthy infants hospitalized with RSV bronchiolitis. Disease severity was determined by the respiratory rate, the duration of hospitalization, and whether patients during their hospitalization required pediatric intensive care unit admission or mechanical ventilation. RSV typing into subgroup A and B was obtained by RT-PCR-hybridization assay. The nasopharyngeal RSV viral loads were measured by real-time quantitative RT-PCR. Disease severity correlated significantly with the presence of risk factor (estimated gestational age < 37 weeks and/or birth weight < 2,500 g) and with chronologic age <or= 28 days at time of sample collection. The results revealed significant association between disease severity and nasopharyngeal RSV viral load. Analysis also showed that disease severity was not associated significantly with RSV subgroup. Thus, RSV disease severity is likely to be determined by an interplay between host and virus factors, including RSV load.

Inter-observer agreement in interpreting chest X-rays on children with acute lower respiratory tract infections and concurrent wheezing

CONTEXT AND OBJECTIVE

Many children with acute lower respiratory tract infections (ALRI) present to the emergency ward with concurrent wheezing. A chest x-ray is often requested to rule out pneumonia. We assessed inter-observer agreement in interpreting x-rays on such children. DESIGNS AND SETTING: Prospective consecutive case study at Instituto de Salud del Niño, Lima, Peru.

METHODS

Chest x-rays were obtained from eligible children younger than two years old with ALRI and concurrent wheezing who were seen in the emergency ward of a nationwide pediatric referral hospital. The x-rays were read independently by three different pediatric residents who were aware only that the children had a respiratory infection. All the children had received inhaled beta-adrenergic agonists before undergoing chest x-rays. Lobar and complicated pneumonia cases were excluded from the study.

RESULTS

Two hundred x-rays were read. The overall kappa index was 0.2. The highest individual kappa values for specific x-ray findings ranged from 0.26 to 0.34 for rib horizontalization and from 0.14 to 0.31 for alveolar infiltrate. Inter-observer variation was intermediate for alveolar infiltrate (kappa 0.14 to 0.21) and for air bronchogram (kappa 0.13 to 0.23). Reinforcement of the bronchovascular network (kappa 0.10 to 0.16) and air trapping (kappa 0.05 to 0.20) had the lowest agreement.

CONCLUSIONS

There was poor inter-observer agreement for chest x-ray interpretation on children with ALRI and concurrent wheezing seen at the emergency ward. This may preclude reliable diagnosing of pneumonia in settings where residents make management decisions regarding sick children. The effects of training on inter-observer variation need further studies.

Phenotype of acute respiratory syncytial virus induced lower respiratory tract illness in infancy and subsequent morbidity

The objective of this study was to investigate the association hypothesis that outcome following respiratory syncytial virus (RSV) induced bronchiolitis (RSVB) and RSV induced wheeze (RSVW) are different. At 3 years respiratory symptoms were more common in those with RSV infection than the control group but there was no increase in allergic sensitisation (11% vs 10%). Those with RSVW were more likely to have evidence of allergic sensitisation when compared with RSVB subjects (22% vs 7%), and have increased symptoms and increased use of inhaled steroids.

CONCLUSION

The data argue that RSV infection during infancy does not induce allergic asthma and that host factors rather than the virus determine long-term outcomes.

Human metapneumovirus and respiratory syncytial virus disease in children, Yemen

Factors increasing the severity of respiratory infections in developing countries are poorly described. We report factors associated with severe acute respiratory illness in Yemeni children (266 infected with respiratory syncytial virus and 66 with human metapneumovirus). Age, indoor air pollution, and incomplete vaccinations were risk factors and differed from those in industrialized countries.

Epidemiologic, socioeconomic, and clinical factors associated with severity of respiratory syncytial virus infection in previously healthy infants

We prospectively quantified disease severity associated with epidemiologic and socioeconomic parameters as well as the clinical factors in 195 previously healthy infants with confirmed respiratory syncytial virus (RSV) infection. Infants were enrolled into three subgroups according to disease severity: outpatients (82 patients), inpatients (100 patients), and intensive care unit patients (13 patients). Epidemiologic parameters such as gestational age, birth weight, chronologic age at presentation, and gender as well as socioeconomic factors such as ethnic origin, family history of asthma, exposure to cigarette smoke, number of family members, presence of pets at home, breast-feeding, and day-care attendance were not found to predict the severity of RSV illness in previously healthy infants. Our results emphasize the complexity of predicting disease severity in previously healthy infants with RSV infection and suggest that other parameters such as host genetic background might explain the clinical variability.

Sibship characteristics and risk of multiple sclerosis: a nationwide cohort study in Denmark

It has been hypothesized that age at infection with a common microbial agent may be associated with the risk of multiple sclerosis (MS). The authors addressed this hypothesis by using number of older siblings and other sibship characteristics as an approximation of age at exposure to common infections. Data on family characteristics and vital status from the Danish Civil Registration System were used to establish a cohort of all Danes whose mothers had been born in Denmark since 1935. Persons diagnosed with MS during the period 1968-1998 were identified through linkage with the Danish Multiple Sclerosis Register. The cohort of 1.9 million Danes was followed for 28.1 million person-years; during that time, 1,036 persons developed MS. Overall, there was no association between number of older siblings, number of younger siblings, total number of siblings, age distance from the nearest younger sibling, or exposure to younger siblings under 2 years of age and risk of MS later in life. There was no association of MS risk with multiple birth (vs. singleton birth) or with the age of the mother or father at birth. These results do not lend support to the hypothesis that number of older siblings or any of the other sibship characteristics studied is associated with risk of MS.

Environmental tobacco smoke exposure: prevalence and mechanisms of causation of infections in children

BACKGROUND AND OBJECTIVES

Environmental tobacco smoke (ETS) exposure is probably one of the most important public health hazards in our community. Our aim with this article is to (1) review the prevalence of ETS exposure in the United States and how this prevalence is often measured in practice and (2) summarize current thinking concerning the mechanism by which this exposure may cause infections in young children.

METHODS

We conducted a Medline search to obtain data published mainly in peer-reviewed journals.

RESULTS

There is still a very high prevalence of ETS exposure among US children ranging from 35% to 80% depending on the method of measurement used and the population studied. The mechanism by which ETS may be related to these infections is not entirely clear but may be through suppression or modulation of the immune system, enhancement of bacterial adherence factors, or impairment of the mucociliary apparatus of the respiratory tract, or possibly through enhancement of toxicity of low levels of certain toxins that are not easily detected by conventional means.

CONCLUSIONS

The prevalence of ETS exposure in the United States is still very high, and its role in causing infections in children is no longer in doubt even if still poorly understood. Research, therefore, should continue to focus on the various mechanisms of causation of these infections and how to best reduce the exposure levels.

[Recommendations for the prevention of respiratory syncytial virus infection]

Premature babies < or = 35 weeks gestation, with or without chronic lung disease (CLD), and infants affected by severe congenital heart disease should be considered high risk population for RSV infection and hospitalization. Hygienic measures and RSV monoclonal antibodies (palivizumab) have been found useful in decreasing rates of RSV hospitalization in these patients. Guidelines for their administration include: a) strongly recommended use in premature babies < or = 28 weeks gestation, or born between 29-32 weeks gestation and less than 6 months at start of RSV station or discharged along it, or affected by CLD in treatment during last 6 months or by severe congenital heart disease. Last two groups could be prophylaxed for two RSV seasons. b) Recommended use among premature babies between 32-35 weeks gestation and less than 6 months of age and presenting two or more risk factors: chronologic age < 10 weeks at start of RSV station, breastfeeding < or = 2 months (physician prescription), sibling < 14 years old, day-care assistance, family history of wheezing, > or = 4 adults at home, airways malformation or neuromuscular disease.

Clinical and socio-economic impact of influenza and respiratory syncytial virus infection on healthy children and their households

This prospective study compared the clinical and socio-economic impact of laboratory-confirmed influenza and respiratory syncytial virus (RSV) infection on healthy children and their families. Among 1,520 otherwise healthy children aged< 15 years attending the Emergency Department for acute conditions other than trauma, influenza viruses and RSV were found in 234 (15.4%) and 116 (7.6%; p<0.0001) patients, respectively. The fact that influenza has a similar global clinical impact on the community to that of RSV infection, but represents a greater socio-economic burden, may contribute to broadening the acceptance of influenza vaccination.

Prospective study of healthcare utilisation and respiratory morbidity due to RSV infection in prematurely born infants

BACKGROUND

A study was undertaken to determine the impact of respiratory syncytial virus (RSV) infection, both in hospital and the community, on healthcare utilisation and respiratory morbidity in prematurely born infants and to identify risk factors for symptomatic RSV infection.

METHODS

A hospital and community follow up study was undertaken of 126 infants born before 32 weeks of gestational age. Healthcare utilisation (hospital admissions and general practitioner attendances) in the first year, respiratory morbidity at follow up (wheeze and cough documented by parent completed diary cards), and RSV positive lower respiratory tract infections (LRTIs) were documented. Nasopharyngeal aspirates were obtained for immunofluorescence and culture for RSV whenever the infants had an LRTI, either in the community or in hospital.

RESULTS

Forty two infants had an RSV positive LRTI (RSV group), 50 had an RSV negative LRTI (RSV negative LRTI group), and 32 infants had no LRTI (no LRTI group). Compared with the RSV negative LRTI and the no LRTI groups, the RSV group required more admissions (p=0.392, p<0.001) and days in hospital (p=0.049, p=0.006) and had more cough (p=0.05, p=0.038) and wheeze (p=0.003, p=0.003) at follow up. Significant risk factors for symptomatic RSV LRTI were number of siblings (p=0.035) and maternal smoking in pregnancy (p=0.005), for cough were number of siblings (p=0.002) and RSV LRTI (p=0.02), and for wheeze was RSV LRTI (p=0.019).

CONCLUSION

RSV infection, even if hospital admission is not required, is associated with increased subsequent respiratory morbidity in prematurely born infants.

Severity of respiratory syncytial virus bronchiolitis is affected by cigarette smoke exposure and atopy

OBJECTIVE

Respiratory syncytial virus (RSV) bronchiolitis is a common cause of hospitalizations in children and has been increasingly identified as a risk factor in the development of asthma. Little is known about what determines the severity of RSV bronchiolitis, which may be helpful in the initial assessment of these children.

DESIGN

We evaluated a variety of environmental and host factors that may contribute to the severity of RSV bronchiolitis in the RSV Bronchiolitis in Early Life prospective cohort study. Severity of bronchiolitis was based on the quantization of lowest O(2) saturation and the length of stay. These factors included the child's and family's demographics, presence of household allergens (dust mite, cat, dog, and cockroach), peripheral blood eosinophil count, immunoglobulin E level, infant feeding, prior illnesses, exposure to intrauterine and postnatal cigarette smoke, and family history of atopy.

PATIENTS

We prospectively enrolled 206 hospitalized infants, all under 12 months old (4.0 +/- 3.3 months old), with their first episode of severe RSV bronchiolitis (mean O(2) saturation: 91.6 +/- 7.3%; length of stay: 2.5 +/- 2.5 days; presence of radiographic opacities: 75%). Patients were excluded for a variety of reasons including previous wheezing, regular use of bronchodilator or antiinflammatory medications, any preexisting lung disease including asthma, chronic lung disease of prematurity/bronchopulmonary dysplasia, or cystic fibrosis; gastroesophageal reflux disease on medical therapy; or congenital anomalies of the chest or lung.

RESULTS

Age was found to be a significant factor in the severity of infection. The younger an infant was, the more severe the infection tended to be as measured by the lowest oxygen (O(2)) saturation. We also found that infants exposed to postnatal cigarette smoke from the mother had a lower O(2) saturation than those not exposed. However, there was no significant difference in RSV bronchiolitis severity between infants exposed only to intrauterine smoke and those infants never exposed to cigarette smoke. Infants with a family history of atopy, especially a maternal history of asthma or hay fever, had a higher O(2) saturation. Although a history of maternal atopy seemed to be protective, there was no association between allergens and bronchiolitis severity, although 25% of households had elevated allergen levels. Black infants demonstrated less severe RSV bronchiolitis than their white counterparts. Multivariate analysis revealed age, race, maternal atopy, and smoking to be associated with severity of RSV bronchiolitis.

CONCLUSION

The severity of RSV bronchiolitis early in life seems modified by postnatal maternal cigarette smoke exposure and atopy and age of the infant, not by levels of allergens in the home environment.

Do environmental pollutants influence the onset of respiratory syncytial virus epidemics or disease severity?

The trigger for annual epidemics of respiratory syncytial virus (RSV) infections and the factors contributing to the disappearance of RSV infections in late winter remain obscure. Similarly, there is no adequate explanation for the higher morbidity and admission rates in industrialised as compared with rural areas. It has been suggested that a variety of environmental factors such as temperature, daylight and humidity may influence the onset and waning of the epidemics. However, the few studies assessing these variables fail to support such a link. In many tropical countries the annual epidemic occurs in the summer or autumn, arguing against temperature having a direct influence. A number of studies have suggested that indoor pollutants, including cigarette smoke, are associated with an increased likelihood of being admitted to hospital with severe lower respiratory tract disease. One study exploring the potential role of outdoor pollutants on the pattern of RSV related illness in infancy was unable to identify a clear link between a variety of pollutants and the timing of the epidemic. Nitric oxide levels were higher in winter than during the summer and much higher winter peaks of NO were observe in industrialised areas as compared with urban and rural areas. Whether this or other environmental pollutants contribute to the higher incidence of severe disease in industrialised areas is unclear. Further work is required to explore the possible influence of NO and other environmental pollutants on both the timing and severity of epidemics.

Identifying risk factors for severe respiratory syncytial virus among infants born after 33 through 35 completed weeks of gestation: different methodologies yield consistent findings

BACKGROUND

Prematurity is a proven risk factor for severe respiratory syncytial virus (RSV) infection. Prematurity leads to an increased need for, and duration of, hospital admission, intensive care, mechanical ventilation and supplemental oxygen, as well as increased mortality.

METHODS

The Pediatric Investigators Collaborative Network on Infections in Canada (PICNIC) study was a prospective, multicenter, cohort study conducted in 16 regions across Canada during 2 successive RSV seasons: November 2000-June 2001, and November 2001-June 2002. The study regions were defined to capture all births and all hospital admissions. The FLIP [identify those risk Factors that most Likely may lead to development of RSV-related respiratory Infection and subsequent hospital admission among Premature infants born 33-35 weeks gestational age (GA)] study was a prospective, case-control study comparison of premature infants hospitalized for RSV infection and infants who had not been hospitalized to identify the risk factors that most likely would lead to development of RSV infection and subsequent hospital admission in this population.

RESULTS

The overall hospitalization rate for RSV in the PICNIC study was 3.6% for infants of 33-35 weeks GA. In the FLIP study, the severity of RSV infection in the 33- to 35-week GA infants was similar to that in the younger infants of <33-week GA studied previously by the Infeccion Respiratoria Infantil por Virus Respiratorio Sincitial Study Group. Similar risk factors were noted in both studies.

CONCLUSIONS

RSV is a major cause of hospitalization in preterm infants. There is great variability among hospital admission rates globally, despite the commonality of severe RSV in many countries. Furthermore there are numerous independent risk factors for severe RSV, including socioeconomic and environmental factors, that merit further investigation. There is likely an additive effect when multiple risk factors are present. More research is needed on the various risk factors and their significance.

Burden of influenza in healthy children and their households

OBJECTIVE

A prospective, multicentre study was conducted to evaluate the burden of laboratory confirmed influenza in healthy children and their household contacts.

METHODS

The patients were enrolled in four emergency departments (EDs) and by five primary care paediatricians (PCPs) in different Italian municipalities 2 days a week between November 1, 2001 and April 30, 2002. The study involved 3771 children less than 14 years of age with no chronic medical conditions who presented with a respiratory tract infection in EDs or PCP outpatient clinics during the study period. Nasopharyngeal swabs were collected for the isolation of influenza viruses and RNA detection. Information was also collected concerning respiratory illnesses and related morbidities among the study children and their household contacts.

RESULTS

Influenza virus was demonstrated in 352 cases (9.3%). In comparison with the influenza negative children, those who were influenza positive had an older mean age, were more often attending day care centres or schools, more frequently experienced fever and croup, received more antipyretics, and had a longer duration of fever and school absence. Furthermore, their parents and siblings had more respiratory illnesses, received more antipyretics and antibiotics, needed more medical visits, missed more work or school days, and needed help at home to care for the ill children for a longer period of time.

CONCLUSIONS

Influenza has a significant clinical and socioeconomic impact on healthy children and their families. Prevention strategies should also focus on healthy children regardless of their age because of their role in disease transmission.

Animal models of sudden unexplained death

The etiology of sudden infant death syndrome (SIDS) is unknown but thought to be multifactorial. Several animal models have been developed that induce death without pre-existing symptoms and with pathology similar to that seen in SIDS infants; however, the relevance of these animal models to the events leading to SIDS remains elusive, in part because animal models are as varied as the potential causes of SIDS. In addition, it is difficult to find an animal model that can accurately reflect the genetic, developmental and environmental risk factors for SIDS. Comparisons between species can prove difficult but animal models provide a useful tool for evaluating potential mechanisms related to sudden unexplained death. This review focuses on models developed to examine the association of infection and inflammation with mechanisms proposed to explain sudden unexplained death.

Adverse health effects of prenatal and postnatal tobacco smoke exposure on children

Parents who choose to smoke are possibly not aware of, or deny, the negative effects of passive smoking on their offspring. This review summarises a wide range of effects of passive smoking on mortality and morbidity in children. It offers paediatricians, obstetricians, specialists in preventive child health care, general practitioners, and midwives an approach to promote smoking cessation in smoking parents before, during, and after pregnancy.

Bronchiolitis caused by respiratory syncytial virus in an area of portugal: epidemiology, clinical features, and risk factors

The aim of the present study was to analyse the clinical and epidemiological characteristics of bronchiolitis caused by respiratory syncytial virus (RSV) in 225 children observed in a paediatric hospital in Lisbon, Portugal, and to determine the clinical, epidemiological, or laboratory parameters that correlate with greater severity of the disease. This prospective study included hospitalised and ambulatory children younger than 36 months of age with a diagnosis of bronchiolitis and was conducted during two consecutive RSV epidemiological seasons (November-March 2000/01 and 2001/02). The median age of the patients was 5 months, and the male-to-female ratio was 1.6:1. RSV was isolated in 60.9% of patients, predominantly in the hospitalised group. The subtype A:B ratio was 7.4:1 and was similar in both seasons. RSV-positive patients were younger, had more severe clinical forms of bronchiolitis, and fewer changes in leucocyte total and differential counts. Among infected patients, higher clinical severity scores occurred in association with first wheezing episodes, overcrowded households, attendance at day-care centres, or prematurity (<36 weeks). This first prospective study of RSV epidemiology in Portugal provides a foundation for appropriate surveillance programmes of RSV infection in this country. A multicentre study is desirable in order to delineate optimal prophylactic and therapeutic guidelines for RSV infection in Portugal.

Environmental and demographic risk factors for respiratory syncytial virus lower respiratory tract disease

OBJECTIVE

To critically review the literature examining risk factors for development of severe respiratory syncytial virus lower respiratory tract infection (RSV LRI).

STUDY DESIGN

A literature review was performed with the use of a MedLine search strategy. Clinical evidence of putative risk factors was rated by means of the US Preventive Services Task Force recommendations, and the quality of the data was critically assessed. Nonmedical risk factors examined included race/ethnicity, age of acquisition of RSV, sex, birth during the first half of the RSV season, breast-feeding, malnutrition, maternal education, socioeconomic status, crowding/siblings, day care, and tobacco smoke exposure.

RESULTS

There was sufficient evidence available to conclude that (1) male sex, (2) age <6 months, (3) birth during the first half of the RSV season, (4) crowding/siblings, and (5) day care exposure are significant risk factors for severe RSV LRI. There was insufficient evidence to evaluate the effect of race/ethnicity on severe RSV LRI. The evidence for tobacco smoke exposure is mixed. Low maternal education (as a proxy for lower socioeconomic status), lack of breast-feeding, and malnutrition did not appear to increase the risk of severe RSV LRI or RSV hospitalization.

CONCLUSIONS

Male sex, young age, birth in the first half of the RSV season, day care attendance, and crowding/siblings are independent risk factors for the development of severe RSV LRI.

Paediatric community-acquired pneumonia: current concept in pharmacological control

Community-acquired pneumonia (CAP) is one of the most frequent infections in childhood but it is not easy to establish a rational therapeutic approach for a number of reasons, including difficulties in identifying the aetiology, the fact that the most frequent bacterial pathogens become resistant to commonly used antibiotics and the lack of certain information concerning the possible preventive role of conjugate vaccines. This leads paediatricians to treat almost all cases of CAP with antibiotics, often using a combination of different antimicrobial classes. In order to avoid unnecessary antibiotic use and limit the spread of antibiotic resistance, consensus guidelines for the management of CAP in childhood should be developed and used by practitioners in their offices and hospitals.

Respiratory syncytial virus epidemics: the ups and downs of a seasonal virus

Respiratory syncytial virus (RSV) is the most common pathogen causing lower respiratory tract infections in infants worldwide. Lower respiratory tract infections caused by RSV occur epidemically, and the appearance of epidemics seems to vary with latitude, altitude and climate. This study uses a review of the literature on RSV seasonality to investigate whether a global pattern in RSV epidemics can be found. A comparison of morbidity and mortality caused by RSV in developed vs. developing countries is also presented. The seasons in which RSV epidemics occur typically depend on geographic location and altitude. During these seasons the epidemics tend to appear in clusters. Although the appearance pattern of these epidemics varies from one continent to another, they usually begin in coastal areas. RSV is the cause of one-fifth of lower respiratory infections worldwide. Generally RSV mortality is low, with a median value of zero. However, RSV mortality in developing countries is significantly higher than RSV mortality in developed countries.

Palivizumab prophylaxis of respiratory syncytial virus disease from 1998 to 2002: results from four years of palivizumab usage

OBJECTIVES

In 1998 the Food and Drug Administration approved palivizumab (Synagis) for the prevention of severe lower respiratory tract infection secondary to respiratory syncytial virus (RSV) in pediatric patients at high risk for developing disease that required hospitalization. In the immediate aftermath of that approval, two retrospective reviews were conducted on 4669 medical records of patients who received at least 1 dose of palivizumab during the 1998 to 1999 and 1999 to 2000 RSV seasons, respectively. These analyses captured data on rates of RSV hospitalization, length of hospital stay, intensive care unit admission and compliance with palivizumab administration. Two prospective US multicenter registry trials followed, during the RSV seasons of 2000 to 2001 and 2001 to 2002. The registries characterized the demographics and outcomes of a total of 7207 high risk infants and children who received prophylaxis for RSV, the risk factors for RSV hospitalization and the patterns and scope of palivizumab usage across 63 and 116 US health care sites, respectively. 1998 TO 1999 PALIVIZUMAB FIRST SEASON OF GENERAL USE: Nine US study sites engaged in a retrospective chart review of infants and children with a gestational age of < or =35 weeks and a chronologic age of <2 years at the time of their first palivizumab injection and who had received at least one dose between September 1998 and May 1999. Of the 1839 prophylaxed children with evaluable data, only 42 (2.3%) were hospitalized with confirmed RSV disease. Of those admitted with confirmed gestational ages, all were premature; the majority were either < 28 weeks gestational age (WGA; 43%) or between 28 and 32 WGA (34%). 1999 TO 2000 PALIVIZUMAB SECOND SEASON OF GENERAL USE: During the 1999 to 2000 RSV season, 12 hospitals and university medical centers, representing a cross-section of US health care facilities, contributed to the second Palivizumab Study Group. The sites collected retrospective data from the charts of 2830 children, all of whom had received at least 1 injection of palivizumab between September 1999 and May 2000. Analysis of 2830 medical records revealed an admission rate of 2.4% (68 of 2830) for confirmed RSV infection, consistent with the overall hospitalization rate of 2.3% from the previous season.

PALIVIZUMAB OUTCOMES REGISTRY

2000 to 2001: Sixty-three sites representing pediatric offices, freestanding clinics and hospital-based clinics participated in a prospective, multicenter, observational study to evaluate the scope of palivizumab usage in a cross-section of US infants. The centers collected outcomes data on RSV-related hospital admissions, injection history and adherence to a standardized palivizumab administration protocol. Of the 2116 infants enrolled 47% were born at < 32 weeks gestation. Patients between 32 and 35 weeks gestational age accounted for another 45% of enrollees. Approximately 8% had a gestational age of >35 weeks. For the 2049 subjects with available follow-up data, the overall confirmed RSV hospitalization rate was 2.9%.

PALIVIZUMAB OUTCOMES REGISTRY

2001 to 2002: Between June 1, 2001 and May 15, 2002, 116 health care centers across the US enrolled 5091 infants in the second prospective Palivizumab Outcomes Registry. As its primary outcome the study measured the occurrence of RSV hospitalization with secondary variables of risk factors for RSV bronchiolitis and compliance with the projected number of palivizumab injections based on month of initial dose. Forty-nine percent (n = 2,501) of the infants were born between 32 and 35 weeks gestational age, 40% (n = 2020) were born at a gestational age of <32 weeks and 11% (n = 570) were born at >35 weeks gestational age. Nineteen percent (n = 964) of these children were deemed at sufficient risk to warrant palivizumab prophylaxis for a second season. Seventy-six of 5084 enrolled subjects experienced a total of 78 RSV-related hospital admissions, for an overall hospitalization rate of 1.5%. Four years of retrospective and prospective data on the use of palivizumab in clinical practice has accumulated a wealth of "real life" information on the clinical effectiveness of RSV immunoprophylaxis in a large cohort of high risk infants from geographically diverse pediatric offices and clinics throughout the United States.

[Pre and postnatal tobacco exposure and bronchiolitis]

OBJECTIVES

To determine the influence of pre- and postnatal tobacco exposure in the development of bronchiolitis.

PATIENTS AND METHODS

A questionnaire was given to the parents of children hospitalized between August 2001 and August 2002. It included items on parental smoking habits and maternal smoking during pregnancy. Clinical, analytical and radiological criteria were used to diagnose bronchiolitis.

RESULTS

Of 450 children, 123 (27.3 %) were diagnosed with bronchiolitis. The control group was composed of 327 children. A total of 61.6 % of the children had at least one parent who smoked and 32.9 % of these children developed bronchiolitis; 39.1 % had non-smoking parents and 18.2 % were hospitalized with bronchiolitis (OR 2.20 [1.39-3.47]). Of the entire group of children studied, 35.3 % had mothers who smoked and 37.7 % of these children had bronchiolitis compared with 21.4 % of children whose mothers were non-smokers (OR 2.22 [1.45-3.39]). A total of 49.6 % had fathers who smoked, and 32.3 % of these children were diagnosed with bronchiolitis compared with 22 % of children whose fathers were non-smokers (OR 1.65 [1.10-2.57]). Forty-four percent of children whose mothers smoked during pregnancy were hospitalized with bronchiolitis compared with only 20.9 % of non-exposed children (OR 2.96 [1.90-4.62]). The large number of mothers who smoked during pregnancy (27.8 %) was notable. Multivariant analysis with logistic regression was performed and the only variable that remained statistically significant was smoking during pregnancy (p < 0.00001; OR 3.27 [1.39-7.71]).

CONCLUSIONS

Maternal smoking during pregnancy seems to be the main risk factor for the subsequent development of bronchiolitis

Impact of severe disease caused by respiratory syncytial virus in children living in developed countries

Among industrialized nations, the rate of rehospitalization in the United States for respiratory syncytial virus (RSV) is approximately 30 per 1000, exceptions being noted for American Indians and Alaskan natives, two ethnic groups who tend toward higher rates of RSV hospitalization. In distinction Japan reports an admission rate of 60 per 1000 for RSV disease. Yet Japan ranks considerably lower than many of its western counterparts in premature births. Whether an RSV subtype, a new viral genotype or some other unifying characteristic exists that might explain the severity of adenovirus, parainfluenza and RSV infections in this region of Asia remains to be determined. Outcomes trials in the United States, Canada, United Kingdom, Denmark and Japan all identified crowding and exposure to tobacco smoke as significant and independent risk factors for disease severity of RSV. The epidemiology of RSV is largely consistent throughout Europe, with peak outbreaks occurring in December and January. In Europe RSV accounts for 42 to 45% of hospital admissions for lower respiratory tract infections in children younger than 2 years of age, and inpatient populations tend to be younger and to experience greater disease severity. For RSV bronchiolitis lengths of stay in European hospitals range from a low of 4 days to a high of 10 days. The Infección Respiratoria Infantil por Virus Respiratorio Sincitial Study Group in Spain conducted 2 prospective observational studies in 14 and 26 neonatal units, respectively, on nonprophylaxed neonates to determine hospitalization rates for respiratory syncytial viral illness during 2 consecutive RSV seasons. Throughout each respiratory season the study group followed premature infants of < or =32 weeks gestational age at birth, representing an annual birth cohort of approximately 100 000 infants. A total of 584 infants who were < or =32 weeks gestational age in the first season and 999 in the second season were followed at monthly intervals. The nonprophylaxed hospitalized group was compared with the nonprophylaxed, nonhospitalized group, and presumptive risk factors were determined for rehospitalization among premature infants. These independent variables, similar for both years, were identified as low gestational age, underlying chronic lung disease, living with school age siblings, exposure to tobacco smoke and a chronologic age of < 3 months at the onset of the RSV season.Stable, yet high rates of admission for RSV illness in Spain were observed in this premature group of < or =32 weeks gestational age: 13.4% for 1999; and 13.1% for the year 2000. Of those hospitalized during the 2 years of the study, 18 and 25%, respectively, were admitted to the intensive care unit. With the exception of higher rates of family allergy, multiple deliveries and a lower rate of neonatal morbidity, prognostic variables for high risk of hospital admission in the year 2000 compared with those of the 1999 sample. Findings from this comprehensive, prospective study served as the basis for the development of standards for the prevention of respiratory syncytial virus infection by the Spanish Society of Neonatology.

Acute viral bronchiolitis and its sequelae in developing countries

Acute viral bronchiolitis (AVB) is a common disease found throughout the world. Various aspects of it are being studied: its epidemiology, diagnosis, prognosis and treatment. Most of these studies are being conducted in developed countries, with only a few taking place in developing countries. Risk factors such as poor nutrition, an adverse environment and early weaning should be studied where these features are common. Treatment aspects such as cost-effectiveness in low income settings need further study. Use of ribavirin and respiratory syncytial virus (RSV)-immunoglobulin are good examples. Post-bronchiolitic sequelae also need to be studied in low income countries. There is evidence that bronchiolitis obliterans is unusually frequent in some Latin-American countries such as Argentina and Brazil. It will be helpful to undertake combined studies in countries with the same socio-economics, investigating the preventive and management aspects of AVB and its sequelae to reduce the morbidity and mortality.