Surveillance for respiratory syncytial virus in infants hospitalized for acute lower respiratory infection in Chile (1989 to 2000)

Cost-savings and health impact of strategies for prevention of Respiratory Syncytial Virus with nirsevimab in Chile based on the integrated analysis of 2019-2023 national databases: A retrospective study

BACKGROUND

In the latter half of 2023, the northern hemisphere initiated the rollout of nirsevimab immunization strategies for infants, yielding promising early results. As Chile prepared for its 2024 strategy implementation, we retrospectively evaluated the potential cost-saving nature of various immunization strategies.

METHODS

Leveraging comprehensive inpatient, outpatient, and sentinel programs data, we conduct a simulation-based retrospective analysis to evaluate the net cost savings of various immunization strategies based on nirsevimab. We first characterize RSV burden among Chilean infants between 2019 and 2023, focusing on medically attended lower respiratory tract infections (MA LRTI), hospital admissions (HA LRTI), and severe cases requiring ICU admission (ICU LRTI). Utilizing nirsevimab efficacy estimates, we simulate counterfactual scenarios to estimate reductions in outpatient visits, hospitalizations, and ICU admissions had nirsevimab been used. We evaluate diverse immunization strategies and estimate their cost-saving status.

FINDINGS

With nirsevimab costing about USD$225 per dose, immunizing infants under 6 months before the RSV season, all newborns during the season, and high-risk groups would have been cost-saving in 2023 and 2019. This strategy would have significantly decreased the strain on the healthcare system during the seasonal surge, reducing 13,533 ICU (77·81/1000 live newborns) and 27,465 hospital bed requirements (157·91/1000 live newborns), alongside 46,886 emergency room visits (269·58/1000 live newborns).

INTERPRETATION

In Chile, a country with a GDP per capita of USD$17,000, various immunization strategies are cost-saving for scenarios comparable to pre-pandemic 2019 and to the particularly severe 2023 when considering only those direct costs associated with patient care, albeit differing in their impact in health outcomes. The resulting decrease in healthcare strain during the Winter virus surge underscores the strategy's impact.

Distinguishing viruses responsible for influenza-like illness

The many respiratory viruses that cause influenza-like illness (ILI) are reported and tracked as one entity, defined by the CDC as a group of symptoms that include a fever of 100 degrees Fahrenheit, a cough, and/or a sore throat. In the United States alone, ILI impacts 9-49 million people every year. While tracking ILI as a single clinical syndrome is informative in many respects, the underlying viruses differ in parameters and outbreak properties. Most existing models treat either a single respiratory virus or ILI as a whole. However, there is a need for models capable of comparing several individual viruses that cause respiratory illness, including ILI. To address this need, here we present a flexible model and simulations of epidemics for influenza, RSV, rhinovirus, seasonal coronavirus, adenovirus, and SARS/MERS, parameterized by a systematic literature review and accompanied by a global sensitivity analysis. We find that for these biological causes of ILI, their parameter values, timing, prevalence, and proportional contributions differ substantially. These results demonstrate that distinguishing the viruses that cause ILI will be an important aspect of future work on diagnostics, mitigation, modeling, and preparation for future pandemics.

Hospital utilization rates for influenza and RSV: a novel approach and critical assessment

BACKGROUND

Influenza and respiratory syncytial virus (RSV) contribute significantly to the burden of acute lower respiratory infection (ALRI) inpatient care, but heterogeneous coding practices and availability of inpatient data make it difficult to estimate global hospital utilization for either disease based on coded diagnoses alone.

METHODS

This study estimates rates of influenza and RSV hospitalization by calculating the proportion of ALRI due to influenza and RSV and applying this proportion to inpatient admissions with ALRI coded as primary diagnosis. Proportions of ALRI attributed to influenza and RSV were extracted from a meta-analysis of 360 total sources describing inpatient hospital admissions which were input to a Bayesian mixed effects model over age with random effects over location. Results of this model were applied to inpatient admission datasets for 44 countries to produce rates of hospital utilization for influenza and RSV respectively, and rates were compared to raw coded admissions for each disease.

RESULTS

For most age groups, these methods estimated a higher national admission rate than the rate of directly coded influenza or RSV admissions in the same inpatient sources. In many inpatient sources, International Classification of Disease (ICD) coding detail was insufficient to estimate RSV burden directly. The influenza inpatient burden estimates in older adults appear to be substantially underestimated using this method on primary diagnoses alone. Application of the mixed effects model reduced heterogeneity between countries in influenza and RSV which was biased by coding practices and between-country variation.

CONCLUSIONS

This new method presents the opportunity of estimating hospital utilization rates for influenza and RSV using a wide range of clinical databases. Estimates generally seem promising for influenza and RSV associated hospitalization, but influenza estimates from primary diagnosis seem highly underestimated among older adults. Considerable heterogeneity remains between countries in ALRI coding (i.e., primary vs non-primary cause), and in the age profile of proportion positive for influenza and RSV across studies. While this analysis is interesting because of its wide data utilization and applicability in locations without laboratory-confirmed admission data, understanding the sources of variability and data quality will be essential in future applications of these methods.

Contribution of Pro-Inflammatory Molecules Induced by Respiratory Virus Infections to Neurological Disorders

Neurobehavioral alterations and cognitive impairment are common phenomena that represent neuropsychiatric disorders and can be triggered by an exacerbated immune response against pathogens, brain injury, or autoimmune diseases. Pro-inflammatory molecules, such as cytokines and chemokines, are produced in the brain by resident cells, mainly by microglia and astrocytes. Brain infiltrating immune cells constitutes another source of these molecules, contributing to an impaired neurological synapse function, affecting typical neurobehavioral and cognitive performance. Currently, there is increasing evidence supporting the notion that behavioral alterations and cognitive impairment can be associated with respiratory viral infections, such as human respiratory syncytial virus, influenza, and SARS-COV-2, which are responsible for endemic, epidemic, or pandemic outbreak mainly in the winter season. This article will review the brain′s pro-inflammatory response due to infection by three highly contagious respiratory viruses that are the leading cause of acute respiratory illness, morbidity, and mobility in infants, immunocompromised and elderly population. How these respiratory viral pathogens induce increased secretion of pro-inflammatory molecules and their relationship with the alterations at a behavioral and cognitive level will be discussed.

Epidemiology of Respiratory Infections

The study of respiratory infections using epidemiologic tools allow the clinician to better understand the most frequently involved agents—viruses and bacteria, which usually originate in humans. Many strategies have been implemented to track the epidemic season of pathogenic agents to improve recognition at a local level, especially for virus detection. A surveillance program implemented a decade ago has allow pediatricians to improve the diagnostic yield on a regular basis.

Incidence and seasonality of respiratory syncytial virus hospitalisations in young children in Denmark, 2010 to 2015

For future decisions on respiratory syncytial virus (RSV)-vaccination strategies and implementation into national immunisation-programmes, we used national registry data (hospitalisation, microbiology and vital statistics) to determine the age-specific incidence and direct medical costs of annual RSV-associated admissions in children < 5 years-old for the period of 2010–2015. We identified ca 2,500 RSV-associated hospitalisations annually amounting to total direct medical-costs of ca EUR 4.1 million per year. The incidence of RSV-associated hospitalisations peaked in infants 1–2 months of age followed by infants 2–3 months of age, and infants < 1 month of age, respectively. Infant boys were at higher risk of severe RSV infection as compared to infant girls: male-to-female ratio peaked with 1.4 at four months of age and gradually levelled out with increasing age to 1.0 at 4 years of age. Five RSV-associated deaths were identified. Our findings demonstrate that in a western country as Denmark, RSV constitutes a considerable burden on childhood health. Furthermore, the best approach to reduce the high incidence of RSV-associated hospitalisations in young infants < 3 months of age may be maternal vaccination due to general challenges in achieving sufficient and protective immune responses in young infants.

One-year observational study of palivizumab prophylaxis on infants at risk for respiratory syncytial virus infection in Latin America

OBJECTIVE

This study aims to describe real world palivizumab use and effectiveness in high-risk Latin American infants and young children.

METHOD

Prospective, multicenter observational study with infants at risk for severe RSV infection who received palivizumab according to routine clinical practice. Subjects were followed for one year with monthly visits after the first dose of palivizumab. An infant was considered adherent if receiving all the expected injections or five or fewer injections within appropriate inter-dose intervals. Annual incidence rates and risk factors of lower respiratory tract infection (LRTI) hospitalization were determined through Poisson regression models (α=0.05).

RESULTS

The study enrolled 458 children from seven countries in Latin America, from February 2011 to September 2012. The majority (98%) were born <36 weeks gestation. Overall, patients received 83.7% of their expected injections and 86.7% completed one year of follow-up. Of the 61 LRTI hospitalizations, 12 episodes were due to RSV infection. The RSV-associated hospitalization rate was 2.9 per 100 patient-years. Bronchopulmonary dysplasia was identified as an independent risk factor for LRTI hospitalization. A total of 1165 adverse events were recorded during one year of follow-up. One hundred and two patients (22.3%) had a total of 135 serious adverse events, but no events were considered to be related to palivizumab.

CONCLUSIONS

The rate of RSV hospitalization in high-risk infants in Latin America was low and aligned with those observed in randomized control trials and observational studies. Palivizumab prophylaxis appeared effective and had a good safety profile in this population.

Potential of small-molecule fungal metabolites in antiviral chemotherapy

Various viral diseases, such as acquired immunodeficiency syndrome, influenza, and hepatitis, have emerged as leading causes of human death worldwide. Scientific endeavor since invention of DNA-dependent RNA polymerase of pox virus in 1967 resulted in better understanding of virus replication and development of various novel therapeutic strategies. Despite considerable advancement in every facet of drug discovery process, development of commercially viable, safe, and effective drugs for these viruses still remains a big challenge. Decades of intense research yielded a handful of natural and synthetic therapeutic options. But emergence of new viruses and drug-resistant viral strains had made new drug development process a never-ending battle. Small-molecule fungal metabolites due to their vast diversity, stereochemical complexity, and preapproved biocompatibility always remain an attractive source for new drug discovery. Though, exploration of therapeutic importance of fungal metabolites has started early with discovery of penicillin, recent prediction asserted that only a small percentage (5-10%) of fungal species have been identified and much less have been scientifically investigated. Therefore, exploration of new fungal metabolites, their bioassay, and subsequent mechanistic study bears huge importance in new drug discovery endeavors. Though no fungal metabolites so far approved for antiviral treatment, many of these exhibited high potential against various viral diseases. This review comprehensively discussed about antiviral activities of fungal metabolites of diverse origin against some important viral diseases. This also highlighted the mechanistic details of inhibition of viral replication along with structure-activity relationship of some common and important classes of fungal metabolites.

Respiratory syncytial virus: a systematic scientometric analysis of the global publication output and the gender distribution of publishing authors

OBJECTIVE

Worldwide, the respiratory syncytial virus (RSV) represents the predominant viral agent causing bronchiolitis and pneumonia in children. To conduct research and tackle existing healthcare disparities, RSV-related research activities around the globe need to be described. Hence, we assessed the associated scientific output (represented by research articles) by geographical, chronological and socioeconomic criteria and analysed the authors publishing in the field by gender. Also, the 15 most cited articles and the most prolific journals were identified for RSV research.

DESIGN

Retrospective, descriptive study.

SETTING

The NewQIS (New Quality and Quantity Indices in Science) platform was employed to identify RSV-related articles published in the Web of Science until 2013. We performed a numerical analysis of all articles, and examined citation-based aspects (eg, citation rates); results were visualised by density equalising mapping tools.

RESULTS

We identified 4600 RSV-related articles. The USA led the field; US-American authors published 2139 articles (46.5%% of all identified articles), which have been cited 83 000 times. When output was related to socioeconomic benchmarks such as gross domestic product or Research and Development expenditures, Guinea-Bissau, The Gambia and Chile were ranked in leading positions. A total of 614 articles on RSV (13.34% of all articles) were attributed to scientific collaborations. These were primarily established between high-income countries. The gender analysis indicated that male scientists dominated in all countries except Brazil.

CONCLUSIONS

The majority of RSV-related research articles originated from high-income countries whereas developing nations showed only minimal publication productivity and were barely part of any collaborative networks. Hence, research capacity in these nations should be increased in order to assist in addressing inequities in resource allocation and the clinical burden of RSV in these countries.

Unexpected Infection Spikes in a Model of Respiratory Syncytial Virus Vaccination

Respiratory Syncytial Virus (RSV) is an acute respiratory infection that infects millions of children and infants worldwide. Recent research has shown promise for the development of a vaccine, with a range of vaccine types now in clinical trials or preclinical development. We extend an existing mathematical model with seasonal transmission to include vaccination. We model vaccination both as a continuous process, applying the vaccine during pregnancy, and as a discrete one, using impulsive differential equations, applying pulse vaccination. We develop conditions for the stability of the disease-free equilibrium and show that this equilibrium can be destabilised under certain extreme conditions, even with 100% coverage using an (unrealistic) vaccine. Using impulsive differential equations and introducing a new quantity, the impulsive reproduction number, we showed that eradication could be acheived with 75% coverage, while 50% coverage resulted in low-level oscillations. A vaccine that targets RSV infection has the potential to significantly reduce the overall prevalence of the disease, but appropriate coverage is critical.

Respiratory syncytial virus hospitalization and mortality: Systematic review and meta-analysis

BACKGROUND

Respiratory syncytial virus (RSV) is a major public health burden worldwide. We aimed to review the current literature on the incidence and mortality of severe RSV in children globally.

METHODS

Systematic literature review and meta-analysis of published data from 2000 onwards, reporting on burden of acute respiratory infection (ARI) due to RSV in children. Main outcomes were hospitalization for severe RSV-ARI and death.

RESULTS

Five thousand two hundred and seventy-four references were identified. Fifty-five studies were included from 32 countries. The global RSV-ARI hospitalization estimates, reported per 1,000 children per year (95% Credible Interval (CrI), were 4.37 (2.98, 6.42) among children <5 years, 19.19 (15.04, 24.48) among children <1 year, 20.01 (9.65, 41.31) among children <6 months and 63.85 (37.52, 109.70) among premature children <1 year. The RSV-ARI global case-fatality estimates, reported per 1,000 children, (95% Crl) were 6.21 (2.64, 13.73) among children <5 years, 6.60 (1.85, 16.93) for children <1 year, and 1.04 (0.17, 12.06) among preterm children <1 year.

CONCLUSIONS

A substantial proportion of RSV-associated morbidity occurs in the first year of life, especially in children born prematurely. These data affirm the importance of RSV disease in the causation of hospitalization and as a significant contributor to pediatric mortality and further demonstrate gestational age as a critical determinant of disease severity. An important limitation of case-fatality ratios is the absence of individual patient characteristics of non-surviving patients. Moreover, case-fatality ratios cannot be translated to population-based mortality. Pediatr Pulmonol. 2017;52:556-569. © 2016 The Authors. Pediatric Pulmonology. Published by Wiley Periodicals, Inc.

Genomic Loads and Genotypes of Respiratory Syncytial Virus: Viral Factors during Lower Respiratory Tract Infection in Chilean Hospitalized Infants

The clinical impact of viral factors (types and viral loads) during respiratory syncytial virus (RSV) infection is still controversial, especially regarding newly described genotypes. In this study, infants with RSV bronchiolitis were recruited to describe the association of these viral factors with severity of infection. RSV antigenic types, genotypes, and viral loads were determined from hospitalized patients at Hospital Roberto del Río, Santiago, Chile. Cases were characterized by demographic and clinical information, including days of lower respiratory symptoms and severity. A total of 86 patients were included: 49 moderate and 37 severe cases. During 2013, RSV-A was dominant (86%). RSV-B predominated in 2014 (92%). Phylogenetic analyses revealed circulation of GA2, Buenos Aires (BA), and Ontario (ON) genotypes. No association was observed between severity of infection and RSV group (p = 0.69) or genotype (p = 0.87). After a clinical categorization of duration of illness, higher RSV genomic loads were detected in infants evaluated earlier in their disease (p < 0.001) and also in infants evaluated later, but coursing a more severe infection (p = 0.04). Although types and genotypes did not associate with severity in our children, higher RSV genomic loads and delayed viral clearance in severe patients define a group that might benefit from new antiviral therapies.

Exploring the dynamics of respiratory syncytial virus (RSV) transmission in children

Respiratory syncytial virus (RSV) is the main cause of lower respiratory tract infections in children. Whilst highly seasonal, RSV dynamics can have either one-year (annual) or two-year (biennial) cycles. Furthermore, some countries show a 'delayed biennial' pattern, where the epidemic peak in low incidence years is delayed. We develop a compartmental model for RSV infection, driven by a seasonal forcing function, and conduct parameter space and bifurcation analyses to document parameter ranges that give rise to these different seasonal patterns. The model is sensitive to the birth rate, transmission rate, and seasonality parameters, and can replicate RSV dynamics observed in different countries. The seasonality parameter must exceed a threshold for the model to produce biennial cycles. Intermediate values of the birth rate produce the greatest delay in these biennial cycles, while the model reverts to annual cycles if the duration of immunity is too short. Finally, the existence of period doubling and period halving bifurcations suggests robust model dynamics, in agreement with the known regularity of RSV outbreaks. These findings help explain observed RSV data, such as regular biennial dynamics in Western Australia, and delayed biennial dynamics in Finland. From a public health perspective, our findings provide insight into the drivers of RSV transmission, and a foundation for exploring RSV interventions.

Biomarkers of respiratory syncytial virus (RSV) infection: specific neutrophil and cytokine levels provide increased accuracy in predicting disease severity

Despite fundamental advances in the research on respiratory syncytial virus (RSV) since its initial identification almost 60 years ago, recurring failures in developing vaccines and pharmacologic strategies effective in controlling the infection have allowed RSV to become a leading cause of global infant morbidity and mortality. Indeed, the burden of this infection on families and health care organizations worldwide continues to escalate and its financial costs are growing. Furthermore, strong epidemiologic evidence indicates that early-life lower respiratory tract infections caused by RSV lead to the development of recurrent wheezing and childhood asthma. While some progress has been made in the identification of reliable biomarkers for RSV bronchiolitis, a "one size fits all" biomarker capable of accurately and consistently predicting disease severity and post-acute outcomes has yet to be discovered. Therefore, it is of great importance on a global scale to identify useful biomarkers for this infection that will allow pediatricians to cost-effectively predict the clinical course of the disease, as well as monitor the efficacy of new therapeutic strategies.

Pro-Inflammatory Cytokines in Nasopharyngeal Aspirate From Hospitalized Children With Respiratory Syncytial Virus Infection With or Without Rhinovirus Bronchiolitis, and Use of the Cytokines as Predictors of Illness Severity

Respiratory syncytial virus (RSV) and human rhinovirus (HRV) respiratory infection in children induce production of inflammatory interleukins (ILs) in the respiratory epithelium. As IL(s) determine the severity of illness, the purpose of this study was to identify the pro-inflammatory IL(s) that could be predictor(s) of clinical severity. One hundred and fifteen patients <2 years old with bronchiolitis due to RSV and /or HRV and 38 controls were selected from a hospital and an outpatient clinic. Clinical data of all patients were recorded. Severity was defined by the number of days with oxygen need. Nasopharyngeal aspirates (NPA) were collected to perform viral diagnosis by quantitative reverse transcription and polymerase chain reaction (qRT-PCR) and to quantify ILs: TNF-α, IL-10, IL-6, IL-1β, and IL-8, by flow cytometry. Simple and multiple regression and receiver operating characteristic (ROC) curves were used for statistical analysis. Of the patients selected 60 were single RSV, 28 RSV associated to HRV, and 27 single HRV. All patients (115) showed significantly higher IL levels when compared with controls. Levels of IL-6, IL-1β, and IL-8 detected in NPA from RSV single and associated to HRV were significantly higher than HRV infected and positively associated with days requiring O2.Levels of IL-6, IL-1β, and IL-8 detected in NPA from patients infected with RSV only or with both RSV and HRV are increased, and any of those 3 cytokines may have a predictive value for the number of days with need of supplemental oxygen.

Superinfection between influenza and RSV alternating patterns in San Luis Potosí State, México

The objective of this paper is to explain through the ecological hypothesis superinfection and competitive interaction between two viral populations and niche (host) availability, the alternating patterns of Respiratory Syncytial Virus (RSV) and influenza observed in a regional hospital in San Luis Potosí State, México using a mathematical model as a methodological tool. The data analyzed consists of community-based and hospital-based Acute Respiratory Infections (ARI) consultations provided by health-care institutions reported to the State Health Service Epidemiology Department from 2003 through 2009.

Central nervous system alterations caused by infection with the human respiratory syncytial virus

Worldwide, the human respiratory syncytial virus (hRSV) is the leading cause of infant hospitalization because of acute respiratory tract infections, including severe bronchiolitis and pneumonia. Despite intense research, to date there is neither vaccine nor treatment available to control hRSV disease burden globally. After infection, an incubation period of 3-5 days is usually followed by symptoms, such as cough and low-grade fever. However, hRSV infection can also produce a larger variety of symptoms, some of which relate to the individual's age at infection. Indeed, infants can display severe symptoms, such as dyspnea and chest wall retractions. Upon examination, crackles and wheezes are also common features that suggest infection by hRSV. Additionally, infection in infants younger than 1 year is associated with several non-specific symptoms, such as failure to thrive, periodic breathing or apnea, and feeding difficulties that usually require hospitalization. Recently, neurological symptoms have also been associated with hRSV respiratory infection and include seizures, central apnea, lethargy, feeding or swallowing difficulties, abnormalities in muscle tone, strabismus, abnormalities in the CSF, and encephalopathy. Here, we discuss recent findings linking the neurological, extrapulmonary effects of hRSV with infection and functional impairment of the CNS.

Respiratory syncytial virus-associated hospitalizations in pre-mature infants in Lima, Peru

We conducted a prospective cohort study in four hospitals in Lima, Peru in infants with a birth weight ≤ 1,500 g followed from birth hospital discharge up to 1 year of age to determine the incidence of respiratory syncytial virus (RSV) hospitalizations. We enrolled 222 infants from March of 2009 to March of 2010: 48 infants with a birth weight < 1,000 g and 174 infants with a birth weight of 1,000-1,500 g (birth weight = 1,197 ± 224 g; gestational age = 30.1 ± 2.6 weeks). There were 936 episodes of respiratory infections; the incidence of respiratory infections during the first 1 year of life was 5.7 episodes/child-years. The incidence of RSV respiratory infections that required emergency room management was 103.9 per 1,000 child-years, and the incidence of RSV hospitalizations was 116.2 per 1,000 child-years (244.9 in infants with a birth weight < 1,000 g and 88.9 in infants 1,000-1,500 g; P < 0.05). The incidence of RSV respiratory infections that required emergency management or hospitalization is high among pre-mature infants in Lima.

Comparison of virological profiles of respiratory syncytial virus and rhinovirus in acute lower tract respiratory infections in very young Chilean infants, according to their clinical outcome

BACKGROUND

Respiratory syncytial virus (RSV) and rhinovirus (HRV) are the main cause of acute lower respiratory tract infections (ALRTIs) in infants. Viral and host-related risk factors for severe disease have also not been clearly established.

OBJECTIVE

To assess whether certain viral features of RSV and, or HRV are associated with severe ALRTI.

STUDY DESIGN

RSV and HRV were studied in nasopharyngeal samples of infants by immunofluorescence, Luminex(®) and/or real-time RT-PCR assays. Quantitation and genotyping of RSV and HRV by PCR were done.

RESULTS

Of 124 virus positive specimens, 74 (59.7%) had RSV; 22 (17.7%) HRV and 28 (22.6%) RSV-HRV co-infection. Hospitalization was required in 57/74 RSV infants (77.0%); in 10/22 HRV cases (45.5%) (p=0.006) and in 15/28 co-infected by both viruses (53.6%) (p=0.003). Severe cases were 33/74 (44.6%) RSV infections, 2/22 HRV cases (9.1%), (p<0.002) and 6/28 (21.4%) patients co-infected by RSV-HRV (p<0.026). Three genotypes (NA1, B7, B9) of RSV circulated during the study. In 33 severe infants, NA1 was detected in 19 cases (57.6%); B7 in 13 (39.4%) and B9 in 1 (3.0%) (p<0.01; OR=10.0). RSV loads were similar between outpatients and hospitalized infants (p=0.7) and among different severities (p=0.7). NA1 loads were higher than other strains (p=0.049). Three geno-groups of HRV circulated homogeneously.

CONCLUSION

In very young infants, RSV cause more severe disease than HRV. Co-infection does not increase the severity of illness. NA1 RSV genotype was associated with major frequency of hospitalization, severe respiratory disease and higher viral load.

Epidemiology of respiratory syncytial virus-associated acute lower respiratory tract infection hospitalizations among HIV-infected and HIV-uninfected South African children, 2010-2011

BACKGROUND

There are limited data on respiratory syncytial virus (RSV) infection among children in settings with a high prevalence of human immunodeficiency virus (HIV). We studied the epidemiology of RSV-associated acute lower respiratory tract infection (ALRTI) hospitalizations among HIV-infected and HIV-uninfected children in South Africa.

METHODS

Children aged <5 years admitted to sentinel surveillance hospitals with physician-diagnosed neonatal sepsis or ALRTI were enrolled. Nasopharyngeal aspirates were tested by multiplex real-time polymerase chain reaction assays for RSV and other viruses. Associations between possible risk factors and severe outcomes for RSV infection among HIV-infected and uninfected children were examined. The relative risk of hospitalization in HIV-infected and HIV-uninfected children was calculated in 1 site with population denominators.

RESULTS

Of 4489 participants, 4293 (96%) were tested for RSV, of whom 1157 (27%) tested positive. With adjustment for age, HIV-infected children had a 3-5-fold increased risk of hospitalization with RSV-associated ALRTI (2010 relative risk, 5.6; [95% confidence interval (CI), 4.5-6.4]; 2011 relative risk, 3.1 [95% CI, 2.6-3.6]). On multivariable analysis, HIV-infected children with RSV-associated ALRTI had higher odds of death (adjusted odds ratio. 31.1; 95% CI, 5.4-179.8) and hospitalization for >5 days (adjusted odds ratio, 4.0; 95% CI, 1.5-10.6) than HIV-uninfected children.

CONCLUSION

HIV-infected children have a higher risk of hospitalization with RSV-associated ALRTI and a poorer outcome than HIV-uninfected children. These children should be targeted for interventions aimed at preventing severe RSV disease.

Cyclovirus in nasopharyngeal aspirates of Chilean children with respiratory infections

Some respiratory tract infections remain unexplained despite extensive testing for common pathogens. Nasopharyngeal aspirates (NPAs) from 120 Chilean infants from Santiago with acute lower respiratory tract infections were analysed by viral metagenomics, revealing the presence of nucleic acids from anelloviruses, adenovirus-associated virus and 12 known respiratory viral pathogens. A single sequence read showed translated protein similarity to cycloviruses. We used inverse PCR to amplify the complete circular ssDNA genome of a novel cyclovirus we named CyCV-ChileNPA1. Closely related variants were detected using PCR in the NPAs of three other affected children that also contained anelloviruses. This report increases the current knowledge of the genetic diversity of cycloviruses whose detection in multiple NPAs may reflect a tropism for human respiratory tissues.

Viral etiology of hospitalized acute lower respiratory infections in children under 5 years of age -- a systematic review and meta-analysis

AIM

To estimate the proportional contribution of influenza viruses (IV), parainfluenza viruses (PIV), adenoviruses (AV), and coronaviruses (CV) to the burden of severe acute lower respiratory infections (ALRI).

METHODS

The review of the literature followed PRISMA guidelines. We included studies of hospitalized children aged 0-4 years with confirmed ALRI published between 1995 and 2011. A total of 51 studies were included in the final review, comprising 56091 hospitalized ALRI episodes.

RESULTS

IV was detected in 3.0% (2.2%-4.0%) of all hospitalized ALRI cases, PIV in 2.7% (1.9%-3.7%), and AV in 5.8% (3.4%-9.1%). CV are technically difficult to culture, and they were detected in 4.8% of all hospitalized ALRI patients in one study. When respiratory syncytial virus (RSV) and less common viruses were included, at least one virus was detected in 50.4% (40.0%-60.7%) of all hospitalized severe ALRI episodes. Moreover, 21.9% (17.7%-26.4%) of these viral ALRI were mixed, including more than one viral pathogen. Among all severe ALRI with confirmed viral etiology, IV accounted for 7.0% (5.5%-8.7%), PIV for 5.8% (4.1%-7.7%), and AV for 8.8% (5.3%-13.0%). CV was found in 10.6% of virus-positive pneumonia patients in one study.

CONCLUSIONS

This article provides the most comprehensive analysis of the contribution of four viral causes to severe ALRI to date. Our results can be used in further cost-effectiveness analyses of vaccine development and implementation for a number of respiratory viruses.

Respiratory syncytial virus infection and recurrent wheezing in Chilean infants: a genetic background?

Respiratory syncytial virus (RSV) infection has been associated to recurrent wheezing, but pathogenic mechanisms are unclear. Interleukin-4/Interleukin-13 (IL-4/IL-13) pathway is involved in both conditions. A common host genetic susceptibility may exist in patients whom RSV will trigger severe illness and those who develop recurrent wheezing.

OBJECTIVE

To assess, by a candidate-gene approach, whether genetic polymorphisms in IL-4/IL-13 pathway are associated with RSV infection severity and its outcome in Chilean children. A cohort of 118 RSV-infected infants was analyzed and followed for one year. Severity of acute infection and later recurrent wheezing were characterized. Alleles and genotypes frequencies were determined for two SNP in each of the genes IL-4, IL-13 and IL-4Rα. Association tests and interaction analyses were performed. Enrollment included 60 moderate and 58 severe cases. Two SNP were found associated to severity during acute infection in IL-4Rα gene (Gln551Arg, Ile50Val). The follow up was completed in 71% of patients (84/118). Later recurrent wheezing was 54% in severe group, versus 31% in moderate cases (p=0.035). In relation to outcome, allele Ile50 in IL-4Rα was more frequent in patients with moderate disease and no wheezing outcome. A common protector genotype is proposed for Chilean children: IL-4Rα Ile/Ile.

CONCLUSION

Genetic variations in the host are associated to infection severity and outcome. A common genetic background might be influencing both pathologies.

The risk of mortality among young children hospitalized for severe respiratory syncytial virus infection

Respiratory syncytial virus (RSV) lower respiratory tract infection (LRTI) is the leading cause of childhood morbidity. Although also an important cause of childhood mortality worldwide, the impact of key risk factors has not been established. A systematic review of 34 articles reporting case fatality rates in young children hospitalized for severe RSV LRTI, according to the presence of underlying RSV risk factors, was conducted. The weighted mean case fatality rate was 1.2% (range, 0-8.3%; median, 0%; n = 10) among preterm infants; 5.2% (range, 2.0-37.0%; median, 5.9%; n = 7) among children with CHD; and 4.1% (range, 0-10.5%; median, 7.0%; n = 6) among children with BPD. Case fatality estimates among children not at high risk (n = 6) ranged from 0% to 1.5% (weighted mean, 0.2%; median, 0.0%). Fatality during hospitalization for severe RSV LRTI is rare among children not at high risk, but occurs more commonly among children at higher risk of RSV LRTI.

Prevalence and clinical characteristics of human respiratory syncytial virus in Chinese adults with acute respiratory tract infection

Respiratory syncytial virus (RSV) is a leading cause of respiratory tract illnesses worldwide. Although the prevalence and clinical manifestations of the two subtypes, RSV-A and RSV-B, have been studied in some detail in infants and young children, they have not been determined in adults. To evaluate the prevalence of the RSV subtypes and disease severity between RSV-A and RSV-B infections in adults, nasal and throat swabs that were collected from patients ≥15 years old who sought medical care for acute respiratory infections at the Fever Clinic of the Peking Union Medical College Hospital in Beijing, China between May 2005 and April 2010. The samples were tested for RSV infection using PCR and sequencing analysis. RSV was detected in 95 (1%) of the adult patients, of whom 53 (55.8%) were positive for RSV-A and 42 (44.2%) for RSV-B. The incidence of RSV infections increased with age (χ(2) = 37.17, P = 1.66E-07). Demographic data and clinical manifestations of RSV-A were similar to those of RSV-B. Although RSV-A and RSV-B co-circulated during the 2005-2006 and 2008-2009 seasons, RSV-A was predominant in the 2006-2008 seasons, whereas RSV-B was predominant in the 2009-2010 season. Upper respiratory tract infections were diagnosed in most RSV-infected patients (n = 80, 84.2%), and three patients suffered from pulmonary infection. This is the first study to provide data on the prevalence and clinical manifestations of RSV subgroups among Chinese adults with fever and acute illness, over five successive epidemic seasons.

Increased expression of the glucocorticoid receptor β in infants with RSV bronchiolitis

OBJECTIVES

The majority of studies on glucocorticoid treatment in respiratory syncytial virus (RSV) bronchiolitis concluded that there are no beneficial effects. We hypothesized that RSV-infected patients may have an increased glucocorticoid receptor (GR) β expression, the isoform that is unable to bind cortisol and exert an antiinflammatory action.

METHODS

By using real-time polymerase chain reaction, we studied the expression of α and β GR in the peripheral blood mononuclear cells obtained from 49 RSV-infected infants (<1 year of age) with severe (n = 29) and mild to moderate (n = 20) illness. In plasma, we analyzed the level of cortisol by radioimmunoassay and inflammatory cytokines interleukin (IL)-10, IL-6, tumor necrosis factor-α, IL-1β, IL-8, IL-12p70, IL-2, IL-4, IL-5, interferon-γ, and IL-17 by cytometric beads assay. Statistical analysis was performed by nonparametric analysis of variance.

RESULTS

We found a significant increase of β GR expression in patients with severe illness compared with those with mild disease (P < .001) and with a group of healthy controls (P < .01). The α:β GR ratio decreased significantly in infants with severe disease compared with those with mild illness (P < .01) and with normal controls (P < .001). The expression of β GR was positively correlated with the clinical score of severity (r = .54; P < .0001).

CONCLUSIONS

The decrease of the α:β GR ratio by an increase of β receptors expression is related to illness severity and may partly explain the insensitivity to corticoid treatment in RSV-infected infants. The increased expression of β GR could be a marker of disease severity.

Role of neutralizing antibodies in adults with community-acquired pneumonia by respiratory syncytial virus

Background. Respiratory syncytial virus (RSV) has been implicated in the etiology of adult community-acquired pneumonia (CAP). We investigated RSV infection in Chilean adults with CAP using direct viral detection, real-time reverse-transcription polymerase chain reaction (rtRT-PCR), and serology (microneutralization assay).

Methods. RSV, other respiratory viruses, and bacteria were studied by conventional and molecular techniques in adults aged ≥18 years presenting with CAP to the healthcare facilities in Santiago, Chile from February 2005 through December 2007.

Results. All 356 adults with CAP enrolled had an acute blood sample collected at enrollment, and 184 had a convalescent blood sample. RSV was detected in 48 cases (13.4%). Immunofluorescence assay and viral isolation each detected only 1 infection (0.2%), whereas rtRT-PCR was positive in 32 (8.9%) cases and serology was positive in 20 (10.8%) cases. CAP clinical characteristics were similar in RSV-infected and non-RSV-infected cases. RSV-specific geometric mean serum-neutralizing antibody titer (GMST) was significantly lower at admission in the 48 RSV-infected cases compared with 308 non-RSV-infected adults (GMST in log₂: RSV/A 8.1 vs 8.9, and RSV/B 9.3 vs 10.4; P < .02).

Conclusions. RSV infection is frequent in Chilean adults with CAP. Microneutralization assay was as sensitive as rtRT-PCR in detecting RSV infection and is a good adjunct assay for diagnostic research. High RSV-specific serum-neutralizing antibody levels were associated with protection against common and severe infection. The development of a vaccine could prevent RSV-related CAP in adults.

Fatality rates in published reports of RSV hospitalizations among high-risk and otherwise healthy children

OBJECTIVE

To review the fatalities among children hospitalized with respiratory syncytial virus (RSV) infection, and identify factors leading to a fatal outcome.

RESEARCH DESIGN AND METHODS

Review of literature identified from a structured search of PubMed (1966-2009) using the following Medical Subject Headings: respiratory syncytial virus infection; hospitalized; infants; and risk factors. Publications were restricted to: English language; full papers; inclusion of > or =10 subjects; children aged < or =18 years, hospitalization for RSV infection; and deaths reported. Case fatality rates were defined as number of deaths divided by number of children hospitalized for RSV and were calculated for each study.

RESULTS

Thirty-six studies met the inclusion and exclusion criteria. Case fatality rates among children hospitalized for RSV ranged from 0 to 33%. In general, studies showed that subgroups of high-risk children (chronic lung disease [CLD] 3.5-23%, congenital heart disease [CHD] 2-37%, and prematurity 0-6.1%) had higher fatality rates than older or otherwise healthy children (consistently <1%). Presence of severe underlying comorbidities such as neuromuscular disease, immunosuppression, and malignancies was associated with death among term and/or older (>1 year) children. Higher fatality rates were reported for infants receiving intensive unit care (1.1-8.6%), extracorporeal life support (33%) or for those who acquired nosocomial RSV infection (0-12.2%). The majority of studies did not report cause of death and clinical details of the fatal cases were often not provided. Other limitations of this review include our search limits, the possibility of inherent bias in our methodology that could result in an under or over estimation of case-fatality rates, and potential publication bias.

CONCLUSIONS

Children at high risk for RSV (CLD, CHD and prematurity), those with severe underlying comorbidities, or those with nosocomial RSV appear to be at increased risk for death after RSV hospitalization. More data are needed on cause of death and how much is directly attributable to RSV.

Identification of P1 types and variants of Mycoplasma pneumoniae during an epidemic in Chile

This study was conducted to determine the types of M. pneumoniae prevalent in adults presenting with community-acquired pneumonia during an epidemic period, and to scrutinize a variable region of the RepMP4 element for the detection of P1 variants. All 23 clinical specimens PCR-positive for M. pneumoniae obtained in two hospitals in Santiago, Chile, from 2005 to 2006 were typed by a multiplex PCR directly and then the RepMP4 fragment of 18 specimens was sequenced. A predominance of M. pneumoniae type 2 was found, 18 (78.3 %) specimens being grouped as type 2 and 5 (21.7 %) as type 1. Co-infection of M. pneumoniae with other respiratory pathogens was found in 10/23 (43.4 %) patients, but their frequency was not related to the M. pneumoniae type. Sequence analysis revealed a single nucleotide polymorphism, a transition mutation, in 50 % of amplicons belonging to type 1 and in 71.4 % of amplicons of type 2. The nucleotide changes were synonymous in each P1 variant. In conclusion, during the 2005–2006 epidemic in Santiago, both types of M. pneumoniae circulated. Although the analysed area in the RepMP4 was small, we detected the existence of P1 variants in the two types of this organism.

Impaired immune response in severe human lower tract respiratory infection by respiratory syncytial virus

BACKGROUND

Respiratory syncytial virus (RSV) is a major cause of acute lower respiratory infection in infants. The immune response plays a leading role in the severity of the disease. We hypothesized that severe RSV disease is associated with an impaired immune response characterized by low circulating T lymphocytes and plasma cytokine concentrations.

METHODS

We evaluate the in vivo immune responses of previously healthy infants with their first proven RSV-acute lower respiratory infection that required hospitalization. According to the clinical severity, defined by using a strict scoring system, the in vivo immune response was compared through the analysis of plasma cytokine values and the phenotyping of peripheral blood lymphocyte and natural killer (NK) cells.

RESULTS

Absolute blood cell counts of CD4+, CD8+, and CD19+ lymphocytes and NK cells were lower in subjects with RSV than in control infants. Lowest cell counts were observed in more severe RSV-infected infants. Significant low values were obtained in CD8+ lymphocytes (P = 0.03) and nonactive NK cells, that express CD94 antigen (P = 0.046). In contrast, activated NK cells that do not express CD94 molecules were significantly higher in RSV infected infants than in healthy controls (% of cells: P = 0.004). The interferon-gamma and tumor necrosis factor-alpha values in RSV infected patients were lower than in controls subjects. Interleukin-17 cytokine was not detected in healthy infants and the largest concentration was found in moderately ill patients as compared with severe cases (P = 0.033). RSV infection showed significantly higher interleukin-8 chemokine than in control infants (P = 0.024).

CONCLUSION

We propose that severe RSV infection in very young infants is associated with poor blood proinflammatory cytokine production, low counts of CD8+ T cells and with a greater activity of a group of NK cells, that are independent of the major histocompatibility complex class Ib recognition system.

Biennial spring activity of human metapneumovirus in Austria

BACKGROUND

Human metapneumovirus (HMPV) is considered an important respiratory pathogen in young children. To gain insight into the seasonality and epidemiologic characteristics of HMPV infection, this study determined the frequency of HMPV infections in hospitalized infants during a 7-year period.

METHODS

By use of real-time reverse-transcriptase polymerase chain reaction, nasopharyngeal aspirates from 1612 infants less than 2 years of age who were hospitalized for acute respiratory tract illness were tested for the presence of HMPV. Weekly HMPV testing data were analyzed to assess the timing of HMPV activity. Season variability was estimated by comparing the onset, duration, peak, and end of outbreaks from October 2000 through October 2007.

RESULTS

Overall, 109 (6.8%) of 1612 cases of acute respiratory illness were associated with HMPV infection. Seasonal HMPV activity varied substantially from year to year, both in prevalence rates of HMPV cases and in seasonal timing of outbreaks. HMPV activity was characterized by a biennial rhythm, with spring seasons occurring every second year, and these accounted for a substantial proportion, up to 30%, of hospitalized cases of acute respiratory tract illness.

CONCLUSIONS

HMPV activity varies substantially from year to year, both in the frequency and timing of illness and shows a biennial pattern of alternating winter and spring activity.

Molecular characterization of hospital-acquired adenovirus infantile respiratory infection in Chile using species-specific PCR assays

BACKGROUND

Adenovirus serotypes 7, 2 and 1 are the second most common cause of viral acute lower respiratory tract infection (ALRI) requiring hospitalization in Chile. Nosocomial outbreaks have high secondary attack and lethality rates, and call for rapid and specific diagnosis.

OBJECTIVE

We compared the results obtained on ALRI specimens by immunofluorescence (IFA) and virus isolation, plus restriction enzyme digestion (RFLP) typing, with universal, species-specific and 7h-specific PCR typing of adenovirus. A second objective was to determine the type of adenovirus implicated in nosocomial infection and nosocomial cross-infection rates.

METHODS

Infants hospitalized for ALRI in the Roberto del Río Children's Hospital (Santiago, Chile) in 1995-1996 had nasopharyngeal aspirates obtained at admission and tested by IFA and virus isolation. Adenovirus isolates were identified by RFLP. When an index case was identified, samples were collected from contacts for 2 consecutive days and twice weekly thereafter for 2 weeks. Further typing of adenovirus isolates was undertaken with universal, species-specific and 7h-specific PCR performed in 2003 on the stored frozen samples.

RESULTS

Fifteen index cases of adenovirus and their 65 contacts were identified. The nosocomial secondary attack rate using PCR was estimated as 46%. PCR had a higher sensitivity (98.7%) compared to virus isolation (90%) and IFA (50%) and facilitated identification of adenovirus strains more easily and accurately than RFLP (91.6% versus 55.8%). Fifty-three percent of the contacts had severe outcomes. The case fatality rate was 16.6% and was associated with adenovirus 7h.

CONCLUSIONS

Prompt, rapid and sensitive methods to identify adenovirus infection are necessary, especially for hospital-acquired adenovirus infections, because of their ease of spread and high fatality rate.

T helper 1/T helper 2 cytokine imbalance in respiratory syncytial virus infection is associated with increased endogenous plasma cortisol

OBJECTIVE

Cellular immunity has classically been described as the defense mechanism for viral infections. The development of cellular or humoral immune responses will depend on a repertoire of cytokines produced by numerous cells, including CD4+ and CD8+ T cells. These lymphocytes can be subdivided into 2 subsets, T helper 1 (Th1) and Th2, on the basis of the cytokine profiles they synthesize. Type 1 T cells produce interferon gamma (IFN-gamma), an essential cytokine in the viral cell-mediated immune response. Th2 cells selectively produce interleukin 4 (IL-4) and IL-5 that participate in the development of humoral immunity and have a prominent role in immediate-type hypersensitivity. An imbalance in the Th1/Th2 cytokine immune response has been related to pathogenesis of the respiratory syncytial virus (RSV) bronchiolitis and to the severity of the infection. Glucocorticosteroids have a role in inhibiting the IFN-gamma response, acting directly on T cells or indirectly through IL-12. In this way, an increase in plasma cortisol would induce a decrease in the Th1 products with the imbalance between Th1/Th2 cytokines and a shift to Th2 response. We hypothesized that there is a relationship among endogenous cortisol response in acute RSV infection, severity of illness, and decreased Th1 cytokine response.

METHODS

We studied 42 infants under 12 months of age during an acute RSV infection. Twenty-one infants with a median age of 6 months had a severe illness and required hospitalization, whereas 21 with mild diseases with a median age of 7 months were under ambulatory control. All of them had bronchial obstruction evidenced by wheezing and/or hyperinflation on chest radiograph and positive RSV antigen detected by indirect immunofluorescence in nasopharyngeal aspirates. The control group included 21 infants in good health matched by age and gender with median age of 6 months that required blood tests for minor surgery. They were evaluated during a non-RSV epidemic period. Heparinized blood was collected on enrollment from all participating children at 9 am for total leukocyte and differential cell count, determination of lymphocyte subsets, and for intracellular detection of cytokines in single cells; mononuclear cells were cultured to determine in the supernatant cytokine production. In addition, 1 mL of plasma was separated and kept frozen at -20 degrees C for cortisol assay. In the supernatant of the cultured peripheral blood mononuclear cells (PBMCs), we quantified IL-12, IFN-gamma, IL-4, IL-5, and IL-10. Lymphocyte phenotypes and CD4+ and CD8+ T cells with intracellular IL-4, IL-10, and IFN-gamma were analyzed by triple-color immunofluorescence of single cells on a FACScan flow cytometer.

RESULTS

Infants with severe illness had significantly higher plasma cortisol levels than infants with mild disease, and in both groups of infected infants, those were higher than in the control group. A significantly decreased IL-12 and IFN-gamma production by PBMCs and a fall in the percentage of CD4+ T cells expressing IFN-gamma were observed only in the severely affected infants. IL-12 concentrations were 2 pg/mL in severe illness versus 13 pg/mL in mildly infected infants and 12 pg/mL in controls. PBMCs from infants with severe illness produced less IFN-gamma than mildly infected infants and than controls when compared with severe illness. No differences between the 3 groups of infants were observed during the acute phase of the disease for IL-4, IL-5, and IL-10. IL-12 and IFN-gamma production had an inverse correlation with plasma cortisol levels. During severe RSV bronchiolitis, infants developed lymphopenia, and significantly lower eosinophil counts and percentages and absolute counts of CD4+ and CD8+ T cells. Eighty days postinfection, all values had returned to normal levels.

CONCLUSIONS

In this study, we demonstrate that during the acute phase of RSV infection, there is an increase in the level of plasma cortisol that is parallel to the decrease in IL-12 and IFN-gamma production. These findings suggest an association between increased plasma cortisol and a decreased Th1-type response. The increase in plasma cortisol was greater in infants with the more severe symptomatology in association with a lower level of IL-12 and IFN-gamma production. The potential causative role of endogenous cortisol in the imbalance of the Th1/Th2 response observed during severe RSV infection requires additional investigation. Our results suggest that the immunologic changes observed in the more severely ill patients may be partially explained by the increased levels of plasma cortisol. This finding should be taken into consideration when systemic steroids are prescribed to infants infected with the RSV because there is still controversy regarding the efficacy of systemic steroid use in severe bronchiolitis.

Intragroup antigenic diversity of human respiratory syncytial virus (group A) isolated in Argentina and Chile

The intragroup antigenic diversity of the G glycoprotein of 226 human respiratory syncytial virus (HRSV) strains isolated in Buenos Aires (Argentina) and Santiago (Chile) between 1995 and 2002 was evaluated by ELISA with a panel of 14 anti-G monoclonal antibodies (MAbs). Out of 226 strains characterized, 172 (76%) belonged to group A and 54 (24%) to group B. Strains from both groups cocirculated throughout the study period in both countries, except in 1996, 2000, and 2002 when only group A strains were isolated. Within group A 23 different antigenic patterns were found as defined by the combination of reactivities with eight strain-specific anti-G MAbs. These antigenic patterns showed different behavior regarding their circulation. Some major patterns were observed in most years with variable proportions; other minor patterns were present in low proportions during 1 or 2 years and then were apparently replaced by new patterns. Some antigenic patterns occurred both in Argentina and Chile during the same epidemics. Since no strain-specific MAbs were available for group B, we could not evidence the antigenic variability within group B. These are the first data on antigenic characterization of HRSV strains isolated in Argentina and Chile. It is shown that the ELISA with MAbs directed against the G protein of RSV is a valuable tool. These results will also provide useful information for further studies to evaluate the antigenic variability of HRSV strains in relation with genetic characteristics.

Molecular epidemiology of human respiratory syncytial virus subgroup A over a six-year period (1999-2004) in Argentina

Human respiratory syncytial virus (HRSV) is the main viral cause of acute lower respiratory tract infections in children. Little information about the molecular epidemiology of HRSV in developing countries, such as Argentina, is available. By RT-PCR, we subgrouped 353 HRSV isolates over six consecutive epidemic seasons (1999-2004) and few isolates from 1997. Between them, 232 (65.7%) belonged to subgroup A and 121 (34.3%) to subgroup B. Therefore, the nucleotide, amino-acid variability and phylogenetic relations of 78 HRSV subgroup A isolates, were analyzed using RFLP and sequence analysis of the G-protein gene. The results showed that there were two main restriction patterns (PA1 and PA2) and two previously described genotypes (GA2 and GA5) cocirculating in Buenos Aires, without evidence of alternation between them during the studied period. The Argentine sequences were compared with previously reported molecular data from other countries. It showed that viruses genetically related circulated the same years within neighboring countries and the sequences from long-distant places were closely related to Argentine sequences, but they belonged to different sampling years. The data reported here support the growing database on the molecular diversity of HRSVA circulating in Latin America in children under 2 years of age and contributes to describe the pattern of global spread of this virus.

Defining the timing of respiratory syncytial virus (RSV) outbreaks: an epidemiological study

Background

Seasonal RSV infections occur every year and affect particularly children under six months of age. Passive immunoprophylaxis with monoclonal antibody Palivizumab is recommended in the period with high risk of RSV infection. This study aims to define the period for the southern part of Germany (Stuttgart area).

Methods

Epidemiological analysis of the RSV situation in southern Germany from 1996 to 2004 and comparison of results with literature was made. The respiratory tract specimens were sent in for the detection of RSV mainly by paediatric clinics. Detection of RSV was carried out mainly by real-time RT-PCR or by ELISA "Pathfinder". RSV outbreaks were depicted as an absolute number and as a percentage of RSV diagnoses in a month. Onsets, offsets, peaks, duration and severity of RSV seasons were defined and analysed.

Results

An early season with strong RSV activity (early-high phase) was followed by a weaker late season (late-low phase) in a regular biennial rhythm. However, onsets, offsets and durations of outbreaks varied significantly from year to year. RSV epidemics in southern Germany were found to oscillate in an antiphase with RSV epidemics in Finland and Sweden.

Conclusion

The long-term regular biennial rhythm allows predicting whether the next outbreak will be late or early and whether RSV activity will be strong or weak. Not foreseeable, however, is the precise time of increase and decrease of RSV activity. Moreover, the regular seasonal pattern may be disrupted by irregular outbreaks. Thus, activity of RSV has to be monitored every year to define the period with high risk of infection.

Management of infants with chronic lung disease of prematurity in Chile

Despite advances in the prevention and management of respiratory distress syndrome, chronic lung disease of prematurity (CLD) remains a major cause of morbidity and mortality in preterm babies in Chile. Its incidence varies from 10% to 60% in different regions of Chile. Since 1998, the management of CLD after discharge from neonatal unit follows national guidelines. Target oxygen saturation is 85% to 91% in the first 1 week of life, 91% to 94% from 1 to 2 weeks and over 95% after 44 weeks postconceptional age. National home oxygen program has improved outcome in infants with CLD. Other specific treatments are used with caution. Diuretics are used for pulmonary oedema. The adverse neurological outcome in infants treated with postnatal steroids restricts its use to infants who cannot be weaned from mechanical ventilation. Inhaled steroids and bronchodilators may reduce asthma-like symptoms in established CLD. Prevention of RSV infection in CLD babies is paramount. The preterm infant population has been maintained under surveillance nationally since 1998.

Palivizumab: a review of its use as prophylaxis for serious respiratory syncytial virus infection

Palivizumab (Synagi) is a humanized monoclonal antibody that provides immunoprophylaxis against serious lower respiratory tract infections (LRTIs) caused by respiratory syncytial virus (RSV). RSV is the leading cause of hospitalization for LRTIs in infants, causing winter- or wet-season epidemics. In two double-blind, placebo-controlled trials, intramuscular palivizumab 15 mg/kg every 30 days for 5 months significantly reduced RSV-related hospitalizations by 55% in 1502 infants with prematurity and/or bronchopulmonary dysplasia/chronic lung disease (BPD/CLD) and by 45% in 1287 infants with hemodynamically significant congenital heart disease (HSCHD). Reductions were statistically significant versus placebo in infants with BPD/CLD, with all degrees of prematurity, and with acyanotic/other heart disease. Palivizumab was generally well tolerated, with < or =1.9% of recipients discontinuing treatment for tolerability reasons. In placebo-controlled trials, the most common potentially drug-related adverse events were fever, nervousness, injection-site reactions, and diarrhea. Drug-related events occurred in 7.2-11% of palivizumab recipients in controlled trials (vs 6.9-10% with placebo) and 0-7.9% in open-label trials. Very few serious potentially drug-related adverse events occurred in clinical trials; four occurred in 2 of 285 patients in one open-label trial. No significant anti-palivizumab antibodies developed during palivizumab use. Palivizumab trough serum concentrations were below the recommended 40 microg/mL in about 33% and up to 14% of children prior to their second and third palivizumab injections. In pharmacoeconomic studies, the cost of palivizumab per hospitalization averted was generally lowest in the highest-risk infants. Drug cost was generally the most influential factor in sensitivity analyses. In conclusion, prophylaxis with palivizumab significantly reduces the incidence of RSV-related hospitalization relative to placebo and is generally well tolerated in high-risk infants aged <2 years, including those with prematurity and BPD/CLD or HSCHD, which are risk factors for early or serious RSV infection. Palivizumab is approved for use in these patients. Other high-risk infants in whom palivizumab has not been formally assessed, such as those with immunodeficiency, cystic fibrosis, or location-specific risk factors (including extended hospital stays) might potentially benefit from palivizumab. The use of palivizumab in these other high-risk populations is likely to be determined as much by pharmacoeconomic considerations as by efficacy outcomes.

Adenovirus and respiratory syncytial virus-adenovirus mixed acute lower respiratory infections in Chilean infants

BACKGROUND

In Chile respiratory syncytial virus (RSV) and adenovirus (AD) are the principal viruses detected in acute lower respiratory infections (ALRI) in infants. An overview of AD pneumonia in Chile to detect annual trends and to compare the severity of single AD or mixed RSV-AD infections is presented.

METHODS

Surveillance in 4927 infants hospitalized for ALRI has been performed from 1989 to 2001 using immunofluorescence assay (IFA) and viral isolation. Clinical features in 117 infants with single genotyped AD and 81 infants with mixed RSV-AD infections were analyzed.

RESULTS

Adenovirus cases declined from 20% annually in the early 1990s to approximately 5% in the 2000 decade. Genotype 7h showed increasing prevalence in hospitalized cases. The mean annual burden of hospitalizations caused by AD in Santiago was estimated to be 0.6%. No difference was observed in duration of fever, oxygen requirement and hospital stay between groups. Lung consolidation was more frequent in AD cases than mixed cases (P < 0.01); interstitial pattern and hyperinflation prevailed in the mixed cases (P < 0.01). No child died. AD diagnosis was confirmed on admission by IFA in 17% of cases of RSV-AD and in 43% of cases of single AD ALRI. AD cases diagnosed early by IFA had worse clinical outcome than those diagnosed later by virus isolation (P < 0.05).

CONCLUSIONS

AD cases declined since 1989. Mixed RSV-AD infections were not more severe than single AD etiology. AD cases admitted with positive IFA had worse prognoses than AD infections diagnosed later by virus isolation.