Respiratory syncytial virus: changes in prevalence of subgroups A and B among Argentinian children, 1990-1996

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.

Genetic diversity in the G protein gene of group A human respiratory syncytial viruses circulating in Riyadh, Saudi Arabia

Human respiratory syncytial virus (HRSV) is a frequent cause of hospitalization and mortality in children worldwide. The molecular epidemiology and circulation pattern of HRSV in Saudi Arabia is mostly uncharted. In the current study, the genetic variability and phylogenetic relationships of HRSV type A strains circulating in Riyadh Province were explored. Nasopharyngeal aspirates were collected from hospitalized children with acute respiratory symptoms during the winter-spring seasons of 2007/08 and 2008/09. Among 175 samples analyzed, 39 (22.3 %) were positive for HRSV by one-step RT-PCR (59 % type A and 41 % type B). Propagation of positive samples in HEp-2 cells permitted the recovery of the first Saudi HRSV isolates. Genetic variability among Saudi HRSV-A strains was evaluated by sequence analysis of the complete attachment (G) protein gene. The nucleotide sequence was compared to representatives of the previously identified HRSV-A genotypes. Sequence and phylogenetic analysis showed that the strains examined in this study were very closely related at both the nucleotide and amino acid level, and all of them are clustered in the GA2 genotype (and mostly belonged to the NA-1 subtype). A total of 23 mutation sites, 14 of which resulted in an amino acid change, were recorded only in Saudi strains. This is the first report on genetic diversity of HRSV-A strains in Saudi Arabia. Further analysis of strains on a geographical and temporal basis is needed to fully understand HRSV-A circulation patterns in Saudi Arabia.

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.

Viral etiology of acute respiratory infections in hospitalized and outpatient children in Buenos Aires, Argentina

OBJECTIVES

To determine and compare the viral frequency, seasonality and clinical-demographic features in 2 groups of children (hospitalized versus outpatients) with acute respiratory infections.

MATERIAL AND METHODS

A cross-sectional, descriptive study was performed from 2008 to 2010 in 620 children <6 years of age with acute respiratory infection. Respiratory samples were studied for classical respiratory viruses by immunofluorescence and for human rhinoviruses (HRV) by real-time reverse transcription polymerase chain reaction. Clinical and demographic data were recorded.

RESULTS

Viral detection by immunofluorescence was 48% in 434 inpatients and 37% in 186 outpatients. Viral diagnosis increased to 83% and 62%, respectively, when testing for HRV. HRV (41%) and respiratory syncytial virus (RSV) (27%) were most common viruses identified, followed by metapneumovirus (9%), influenza A and parainfluenza (3%), adenovirus and influenza B (2%). HRV frequency was significantly higher in hospitalized patients (47%) than in outpatients (27%) (P < 0.001). Coinfection was detected in 12% of hospitalized and 4% of outpatients (P < 0.031). HRV and adenovirus circulated throughout the entire year. RSV, influenza A and B predominated in winter, whereas metapneumovirus and parainfluenza predominated in spring. Of 362 patients with bronchiolitis, 84% had a virus identified; HRV (42%) and RSV (38%) were predominant. Of 77 patients with pneumonia, 84% had a virus detected with HRV (43%) and RSV (29%) predominating.

CONCLUSIONS

HRV were significant pathogens associated with bronchiolitis and pneumonia, especially in hospitalized patients. Both, HRV and coinfections, were risk factors for hospitalization. These findings support the importance of including HRV detection in children with acute respiratory infection.

Circulating strains of human respiratory syncytial virus in central and south America

Human respiratory syncytial virus (HRSV) is a major cause of viral lower respiratory tract infections among infants and young children. HRSV strains vary genetically and antigenically and have been classified into two broad subgroups, A and B (HRSV-A and HRSV-B, respectively). To date, little is known about the circulating strains of HRSV in Latin America. We have evaluated the genetic diversity of 96 HRSV strains by sequencing a variable region of the G protein gene of isolates collected from 2007 to 2009 in Central and South America. Our results show the presence of the two antigenic subgroups of HRSV during this period with the majority belonging to the genotype HRSV-A2.

A decade of respiratory syncytial virus epidemiology and prophylaxis: translating evidence into everyday clinical practice

Respiratory syncytial virus (RSV) is a common infection in infancy, with nearly all children affected by two years of age. Approximately 0.5% to 2.0% of all children are hospitalized with lower respiratory tract disease, of which 50% to 90% have bronchiolitis and 5% to 40% have pneumonia. Morbidity and mortality are highest in children with nosocomial infection and in those with underlying medical illnesses such as cardiac and chronic lung disease. Aboriginal children residing in remote northern regions are specifically considered to be at high risk for hospitalization due to RSV infection. Thorough hand washing and health education are the principal strategies in primary prevention. In the absence of a vaccine, palivizumab prophylaxis is currently the best intervention to reduce the burden of illness and RSV-related hospitalization in high-risk children. Health care professionals should provide palivizumab prophylaxis cost effectively in accordance with recommendations issued by pediatric societies and national advisory bodies. The present article reviews the epidemiology of RSV infection and the short- and long-term impact of disease in high-risk infants and special populations. Prevention strategies and treatment are discussed based on the existing scientific evidence, and future challenges in the management of RSV infection are addressed.

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.

Molecular epidemiology of human respiratory syncytial virus in Uruguay: 1985-2001--a review

The variability of the G glycoprotein from human respiratory syncytial viruses (HRSV) (groups A and B) isolated during 17 consecutive epidemics in Montevideo, Uruguay have been analyzed. Several annual epidemics were studied, where strains from groups A and B circulated together throughout the epidemics with predominance of one of them. Usually, group A predominates, but in some epidemics group B is more frequently detected. To analyse the antigenic diversity of the strains, extracts of cells infected with different viruses of group A were tested with a panel of anti-G monoclonal antibodies (MAbs). The genetic variability of both groups was analyzed by sequencing the C-terminal third of the G protein gene. The sequences obtained together with previously published sequences were used to perform phylogenetic analyses. The data from Uruguayan isolates, together with those from the rest of the world provide information regarding worldwide strain circulation. Phylogenetic analyses of HRSV from groups A and B show a model of evolution analogous to the one proposed for influenza B viruses providing information that would be beneficial for future immunization programs and to design safe vaccines.

Genetic and antigenic variability of human respiratory syncytial virus (groups a and b) isolated over seven consecutive seasons in Argentina (1995 to 2001)

The genetic and antigenic variability of human respiratory syncytial virus (HRSV) strains isolated in Buenos Aires from 1995 to 2001 was evaluated by partial nucleotide sequencing of the G gene and enzyme-linked immunosorbent assay analysis with anti-G monoclonal antibodies. Phylogenetic analyses showed that 37 group A strains clustered into five genotypes, whereas 20 group B strains clustered into three genotypes. Group A showed more genetic variability than group B. A close correlation between genotypes and antigenic patterns was observed. Changes detected in the G protein of viruses from both groups included (i) amino acid substitutions and(ii) differences in protein length due to either changes in stop codon usage or sequence duplications. Three B strains from 1999 exhibited a duplication of 20 amino acids, while one B strain from 2001 had 2 amino acids duplicated. The comparison among Argentinean HRSV strains and viruses isolated in other geographical areas during different epidemics is discussed.

Genetic diversity of respiratory syncytial virus isolated during an epidemic period from children of northeastern Brazil

Outbreaks of human respiratory syncytial virus (HRSV) are the leading cause of serious acute lower respiratory viral disease in many countries in different continents. Data on clinical and epidemiological aspects of HRSV infections in this country have been reported, but there is lack of data regarding the molecular epidemiology of this virus in Salvador. The genetic variability of HRSV isolated during an outbreak in Salvador, Brazil (1999) has been analysed. Partial sequences of the G protein gene of 13 isolates from antigenic group A and 4 isolates from antigenic group B of HRSV were determined. Nucleotide sequences of C-terminal G gene were compared to sequences of HRSV isolates from countries of South America and from the rest of the world available at the GenBank. Brazilian group A and B isolates were clustered into previously characterised genotypes: GA5, GA2, GA7, and GB3, SAB3, respectively. This is the first study of GA7 and SAB3 genotypes circulation in South American countries. It is interesting to point out that viruses isolated in Salvador appear to be closer related with those from Montevideo-Uruguay and Buenos Aires, Argentina strains, suggesting circulation of similar strains among different South American countries in different seasons. Moreover, viruses closely related genetically circulated in the same year in Salvador and distant places such as Mozambique, supporting the previous suggestion on the complexity of HRSV strain circulation patterns, and the high capability of HRSV spreading world-wide.

Antigenic and genetic variability of human respiratory syncytial viruses (group A) isolated in Uruguay and Argentina: 1993-2001

The antigenic and genetic diversity of G glycoprotein from 25 human respiratory viruses (group A) isolated during nine consecutive epidemics (1993-2001) in Montevideo, Uruguay, and 7 strains isolated in Buenos Aires, Argentina, in the same period were analyzed. Genetic variability was evaluated by partial sequence of the G protein gene. Phylogenetic analysis indicated that most Uruguayan and Argentinean group A isolates clustered into three genotypes: GA5, GA2, and GA1. Some strains clustered into the GA3 genotype characterized previously. The antigenic analysis was carried out with a panel of anti-G monoclonal antibodies that recognized conserved and strain-specific epitopes. A close correlation between the antigenic and genetic relatedness of the strains analyzed was observed.

Effect of palivizumab prophylaxis in decreasing respiratory syncytial virus hospitalizations in premature infants

BACKGROUND

Respiratory syncytial virus (RSV) is a major cause of hospitalization in preterm infants and infants with chronic lung disease (CLD). Palivizumab, a humanized monoclonal antibody, was approved in Europe in 1999 as prophylaxis against severe RSV-related respiratory illness. No multiple season data have been published on palivizumab effectiveness in European populations. Data collected during 4 years in Spain compared RSV hospitalization rates and risk factors in a cohort of palivizumab-prophylaxed and nonprophylaxed preterm infants.

METHODS

The first cohort was derived from 2 previous studies and included 1583 infants followed during 2 RSV seasons (1998 to 1999, 1999 to 2000) before palivizumab initiation in Spain. The second cohort included 1919 infants who received palivizumab prophylaxis for 2 subsequent respiratory seasons (2000 to 2001, 2001 to 2002). Both cohorts were preterm (< or =32 weeks gestational age) and < or =6 months old at onset of RSV season.

RESULTS

The RSV hospitalization rate in the palivizumab-prophylaxed cohort was 3.95, and it was 13.25% in nonprophylaxed infants This 70% overall difference in RSV hospitalization was observed despite the palivizumab-prophylaxed group's lower gestational ages, more severe neonatal intensive care unit respiratory courses and higher incidence of CLD. Significant risk factors for RSV hospitalization in both cohorts included: lower gestational age; chronologic age <3 months at RSV season onset; school age siblings; and lower parental education. Nonprophylaxed children had a higher risk for RSV-related hospitalization than did prophylaxed patients (odds ratio, 3.86; 95% confidence interval, 2.83 to 5.25).

CONCLUSION

Data from this study support the effectiveness of palivizumab in significantly modifying RSV-related hospitalizations in high risk preterm infants, with and without CLD, during two respiratory seasons.

RSV molecular characterization and specific antibody response in young children with acute lower respiratory infection

The presence of respiratory syncytial virus (RSV) in nasopharyngeal aspirates (NPA) were studied in 254 hospitalized Argentinean children with acute lower respiratory infection tract (ALRI). The specific humoral immune response and partial sequences of the G protein gene were studied in a subset of 22 children with RSV confirmed infection. The RSV IgM detection and the RSV IgG titration were made by immunofluorescence assay (IFA) in pairs of sera. The partial RSV G gene sequences were obtained by an RT-PCR amplification directly from de NPAs. RSV was present in 44.5% of the children. The RSV IgM was detected in 22.7 and 68.8% of the first and second sera, respectively. The IgG geometric mean titers of the acute and convalescent sera were 8 and 589. The RSV IgG titration was able to define 86.4% of the RSV confirmed cases. The percentage of coincidence between RSV IgM detection in the second sera and diagnosis by RSV IgG titration was 72.7% and no significant differences were observed. The nucleotide sequence of one group A and three group B viruses were identified. The first one was related with circulating viruses in Madrid, Montevideo and Mozambique during 1992, 1989 and 1999, respectively. The three sequences identified as group B viruses were closely related with circulating viruses in 1998 from South Africa and Canada during 1999 and 2000. The data obtained in our study provide the first approach at the molecular level (nucleotide) of the RSV circulating strains in Argentina and the lack of genotype patterns previously determined make necessary a continuous molecular surveillance in order to contribute to the understanding of the behavior of this virus in our community.

Current strategies in the prevention of respiratory syncytial virus disease

Infants infected with respiratory syncytial virus (RSV) develop both upper and lower respiratory tract infections resulting in laryngotracheobronchitis, bronchiolitis and pneumonia. Premature infants of less than 32 weeks' gestation and those with underlying chronic lung disease are particularly susceptible and incur significant morbidity and mortality following hospitalisation. Conservative RSV prevention strategies focus on the interruption of transmission by proper hand-washing techniques and reducing exposure to potential environmental risk factors. Major challenges have impeded the development of an RSV vaccine but a licensed product may be expected in the near future. Prophylaxis with a humanised mouse monoclonal antibody (palivizumab) has been effective in reducing the rate of RSV hospitalisation in high-risk premature infants in phase II-IV trials and is available for use within internationally approved guidelines. Experimental studies evaluating the use of palivizumab in patients with congenital heart disease, those with cystic fibrosis and immunosuppressed bone marrow transplant recipients are well underway, the results of which are eagerly awaited.

Occurrence and severity of infections caused by subgroup A and B respiratory syncytial virus in children in southeast Brazil

The frequency and severity of infections caused by respiratory syncytial virus (RSV) were assessed in children <2 years of age seen at the emergency department. The frequency of RSV detection in the clinical virology laboratory during the past 3 years was also analyzed retrospectively. RSV was found in 21.6% (188/869) of the samples collected from children seen at the emergency department and was found to be more frequent during the autumn, being less frequent or negligible by midwinter. RSV subgroups A and B co-circulated within the same time period in children seen at the emergency department, with varying predominance of either subgroup. There was no significant association of RSV subgroup with disease severity, but only a trend for RSV subgroup B being more frequent in children with risk factors for severe disease.

Multicentered study of viral acute lower respiratory infections in children from four cities of Argentina, 1993-1994

This study describes the first multicentered study of acute lower respiratory infection viral etiology in young children from four different geographical areas of Argentina. A total of 1,278 children under 5 years of age, hospitalized in primary care centers from Buenos Aires, Córdoba, Santa Fé and Mar del Plata cities during a 2-year period were studied (1993-1994). Nasopharyngeal aspirates were investigated for respiratory syncytial virus (RSV), adenovirus, parainfluenza, and influenza A and B viruses by indirect immunofluorescence. Out of the patients studied, 946 (74%) were under 1 year of age. Viruses were detected in 399 patients (32%). RSV was observed in 25.3% of the samples, representing 78.2% of all viral positive cases. Adenoviruses were detected in 2.5% of the cases, parainfluenza in 2.2%, influenza A in 2.1%, and influenza B in 0.2%. Compared with other viruses, the higher RSV frequency was statistically significant (P < 0.000). Most RSV cases were detected between May and September with a significant peak in July (P < 0.000). Pneumonia was observed in 46% of the patients, bronchiolitis in 41% and other entities in 13%. The case fatality rate observed during the 2 year study was 0.73%. Most of the above respiratory viruses were detected in the four cities, however, the frequency of RSV and influenza were different in the southern city.

Molecular epidemiology of respiratory syncytial virus

Human respiratory syncytial virus (RSV) is the major cause of lower respiratory tract disease in infants. It is unusual in that it causes repeated infections throughout life. Despite considerable efforts there is as yet no satisfactory vaccine available. This paper reviews the molecular epidemiology of the RSV and describes the complex genotypic structure of RSV epidemics. The evolution of the virus is discussed, with particular reference to the antigenic and genetic variability of the attachment glycoprotein.