Respiratory Syncytial Virus: New Challenges for Molecular Epidemiology Surveillance and Vaccination Strategy in Patients with ILI/SARI

Whole-Genome Sequencing and Genetic Diversity of Human Respiratory Syncytial Virus in Patients with Influenza-like Illness in Sicily (Italy) from 2017 to 2023

Monitoring the genetic variability of human respiratory syncytial virus (hRSV) is of paramount importance, especially for the potential implication of key antigenic mutations on the emergence of immune escape variants. Thus, to describe the genetic diversity and evolutionary dynamics of hRSV circulating in Sicily (Italy), a total of 153 hRSV whole-genome sequences collected from 770 hRSV-positive subjects between 2017 and 2023, before the introduction of expanded immunization programs into the population, were investigated. The phylogenetic analyses indicated that the genotypes GA.2.3.5 (ON1) for hRSV-A and GB.5.0.5a (BA9) for hRSV-B co-circulated in our region. Amino acid (AA) substitutions in the surface and internal proteins were evaluated, including the F protein antigenic sites, as the major targets of immunoprophylactic monoclonal antibodies and vaccines. Overall, the proportion of AA changes ranged between 1.5% and 22.6% among hRSV-A, whereas hRSV-B varied in the range 0.8-16.9%; the latter was more polymorphic than hRSV-A within the key antigenic sites. No AA substitutions were found at site III of both subgroups. Although several non-synonymous mutations were found, none of the polymorphisms known to potentially affect the efficacy of current preventive measures were documented. These findings provide new insights into the global hRSV molecular epidemiology and highlight the importance of defining a baseline genomic picture to monitor for future changes that might be induced by the selective pressures of immunological preventive measures, which will soon become widely available.

What 'case definition' for respiratory syncytial virus infection? Results of a systematic literature review to improve surveillance among the adults

BACKGROUND

Human respiratory syncytial virus (hRSV) is a leading cause of acute lower respiratory tract infection in frail individuals, including children, the elderly and immunocompromised people, with mild to severe symptoms. World Health Organization claims hRSV causes most elderly influenza-like illnesses (ILI) and severe acute respiratory infections (SARI). In this study, different case definitions for hRSV surveillance were examined for accuracy.

METHODS

The following search query ('Respiratory Syncytial Virus' OR 'RSV' OR 'hRSV' AND 'case definition') was used on PubMed/MEDLINE and Scopus with a 15-year-old baseline age restriction to conduct a systematic literature review.

RESULTS

Of 12 records, 58% employed the SARI definition, 50% the ILI definition and 42% the acute respiratory infection (ARI) definition, with some overlap. In young adults (18-64 years old), most studies show RSV prevalence between 6.25 and 72.54 cases per 1000 per year, and 19.23 to 98.5 in older adults. The outpatient ARI and hospitalized SARI criteria are particularly sensitive and specific.

CONCLUSIONS

Disease burden measurement requires a clear case definition; however, current literature is questionable. Currently, hRSV surveillance uses numerous case definitions with debatable accuracy. The epidemiology, clinical characteristics, and disease burden of hRSV are difficult to characterize without a standard surveillance case definition.

Birth characteristics as predictors of respiratory syncytial virus hospitalisation in newborns to optimise immunisation schedule

AIM

To examine birth characteristics that influence infant respiratory syncytial virus (RSV) hospitalisation risk in order to identify risk factors for severe RSV infections.

METHODS

Retrospective cohort study of 460 771 Sicilian children under 6 months old from January 2007 to December 2017. Hospital discharge records were consulted to identify cases and hospitalisations with International Classification of Diseases, Ninth Revision, Clinical Modification codes 466.11 (RSV bronchiolitis), 480.1 (RSV pneumonia) and 079.6 (RSV). RSV hospitalisation risk was estimated using adjusted odds ratios (aOR) and 95% confidence intervals (95% CI).

RESULTS

Overall, 2420 (5.25 per 1000 infants) RSV-related hospitalisations were identified during the study, with girls accounting for 52.8%. RSV hospitalisation risk increased for full-term, transferred, extreme immature, and preterm neonates with serious issues (aOR 3.25, 95% CI 2.90-3.64; aOR 1.86, 95% CI 1.47-2.32; aOR 1.54, 95% CI 1.11-2.07; and aOR 1.48, 95% CI 1.14-1.90). Compared to children born in June, the risk of RSV hospitalisation was significantly higher in children born in January (aOR 28.09, 95% CI 17.68-48.24) and December (aOR 27.36, 95% CI 17.21-46.99).

CONCLUSION

This study identified birth month and diagnosis-related groups as key predictors of RSV hospitalisations. This could help manage monoclonal antibody appropriateness criteria.

Epidemiology and burden of respiratory syncytial virus in Italian adults: A systematic review and meta-analysis

OBJECTIVE

Respiratory syncytial virus (RSV) is a common respiratory pathogen not only in children, but also in adults. In view of a recent authorization of adult RSV vaccines in Italy, our research question was to quantify the epidemiology and burden of RSV in Italian adults.

METHODS

Observational studies on the epidemiology and clinical burden of laboratory-confirmed or record-coded RSV infection in Italian adults of any age were eligible. Studies with no separate data for Italian adults, modeling and other secondary publications were excluded. A literature search was performed in MEDLINE, Biological Abstracts, Global Health, Scopus and Web of Science on 22 November 2023. Critical appraisal was performed by means of a Joanna Briggs Institute checklist. Random-effects (RE) meta-analysis was performed to obtain pooled estimates and the observed heterogeneity was investigated by subgroup and meta-regression analyses. The protocol was prospectively registered (doi.org/10.17504/protocols.io.5qpvo32odv4o/v1).

RESULTS

Thirty-five studies were identified, most of which had at least one possible quality concern. RSV seasonal attack rates ranged from 0.8 ‰ in community-dwelling older adults to 10.9% in hematological outpatients. In the RE model, 4.5% (95% CI: 3.2-5.9%) of respiratory samples tested positive for RSV. This positivity prevalence was higher in older adults (4.4%) than in working-age adults (3.5%) and in outpatient (4.9%) than inpatient (2.9%) settings. According to the meta-regression, study location and sample size were also significant predictors of RSV detection frequency. The pooled estimate of in-hospital mortality was as high as 7.2% (95% CI: 4.7-10.3%). Data on other indicators of the diseases burden, such as complication and hospitalization rates, were unavailable.

CONCLUSION

RSV poses a measurable burden on Italian adults, especially those of older age and with some co-morbidities. However, several data on the natural history of RSV disease are missing and should be established by future large-scale studies.

Management of Acute Bronchiolitis in Spoke Hospitals in Northern Italy: Analysis and Outcome

Bronchiolitis is an acute viral infection of the lower respiratory tract that affects infants and young children. Respiratory syncytial virus (RSV) is the most common causative agent; however, other viruses can be involved in this disease. We retrospectively reviewed the clinical features of infants aged less than 12 months hospitalized for acute bronchiolitis in our Pediatric Units of Chivasso, Cirié, and Ivrea in Piedmont, Northern Italy, over two consecutive bronchiolitis seasons (September 2021-March 2022 and September 2022-March 2023). Patient-, disease-, and treatment-related variables were analyzed. The probability of therapeutic success (discharge home) was 96% for all patients (93% for RSV vs. 98% for non-RSV patients, p > 0.05). Among 192 patients, 42 infants (22%) underwent high-flow oxygen support (HFNC), and only 8 (4%) needed to be transferred to our hub referral hospital. Factors associated with hub hospital transfer were the age under 1 month and the failure of HFNC. The wide and increasing use of HFNC in pediatric inpatients improved the management of bronchiolitis in Spoke hospitals, reducing transfer to a hub hospital provided with Intensive Care Units.

Epidemiology and molecular analyses of respiratory syncytial virus in the 2021-2022 season in northern Italy

Background

Human respiratory syncytial virus (RSV) is the leading cause of acute lower respiratory tract infection among infants and young children worldwide, with seasonal peaks in January and February. This study aimed to characterize the RSV samples from a pediatric cohort in the 2021-2022 season in Italy.

Methods

In total, 104 samples were collected from pediatric patients attending the "Vittore Buzzi" Children's Hospital in Milan, Italy in the 2021-2022 season. RT-PCR and next-generation sequencing were used to discriminate subgroups and obtain whole genomes. Maximum likelihood and Bayesian phylogenetic methods were used to analyze Italian sequences in the European contest and date Italian clusters.

Results

The median age was 78 days, and 76.9% of subjects required hospitalization, with a higher proportion of patients under 3 months of age. An equal proportion of subgroups A (GA2.3.5) and B (GB5.0.5a) was found, with significant differences in length of hospitalization, days of supplemental oxygen treatment, and intravenous hydration duration. Phylogeny highlighted 26 and 37 clusters containing quite the total of Italian sequences for RSV-A and -B, respectively. Clusters presented a tMRCA between December 2011-February 2017 and May 2014-December 2016 for A and B subgroups, respectively. Compared to European sequences, specific mutations were observed in Italian strains.

Conclusion

These data confirmed a more severe clinical course of RSV-A, particularly in young children. This study permitted the characterization of recent Italian RSV whole genomes, highlighting the peculiar pattern of mutations that needs to be investigated further and monitored.

Genomic monitoring of SARS-CoV-2 variants using sentinel SARI hospital surveillance

Background

To support the COVID-19 pandemic response, many countries, including Belgium, implemented baseline genomic surveillance (BGS) programs aiming to early detect and characterize new SARS-CoV-2 variants. In parallel, Belgium maintained a sentinel network of six hospitals that samples patients with severe acute respiratory infections (SARI) and integrated SARS-CoV-2 detection within a broader range of respiratory pathogens. We evaluate the ability of the SARI surveillance to monitor general trends and early signals of viral genetic evolution of SARS-CoV-2 and compare it with the BGS as a reference model.

Methods

Nine-hundred twenty-five SARS-CoV-2 positive samples from patients fulfilling the Belgian SARI definition between January 2020 and December 2022 were sequenced using the ARTIC Network amplicon tiling approach on a MinION platform. Weekly variant of concern (VOC) proportions and types were compared to those that were circulating between 2021 and 2022, using 96,251 sequences of the BGS.

Results

SARI surveillance allowed timely detection of the Omicron (BA.1, BA.2, BA.4, and BA.5) and Delta (B.1.617.2) VOCs, with no to 2 weeks delay according to the start of their epidemic growth in the Belgian population. First detection of VOCs B.1.351 and P.1 took longer, but these remained minor in Belgium. Omicron BA.3 was never detected in SARI surveillance. Timeliness could not be evaluated for B.1.1.7, being already major at the start of the study period.

Conclusions

Genomic surveillance of SARS-CoV-2 using SARI sentinel surveillance has proven to accurately reflect VOCs detected in the population and provides a cost-effective solution for long-term genomic monitoring of circulating respiratory viruses.

Human Respiratory Syncytial Virus Epidemiological Burden in Pediatric Outpatients in Italy: A Systematic Review

BACKGROUND

Human respiratory syncytial virus (hRSV) is a key contributor to lower respiratory tract infections (LRTIs), affecting children aged 0-5 years and often leading to outpatient visits, emergency department utilization, and hospitalization. With the development of hRSV vaccines for mitigation, understanding the epidemiological impact of hRSV infections among 0-5-year-old pediatric outpatients in Italy is crucial.

METHODS

This systematic review conducted searches on PubMed, Embase, Scopus, and the International HTA Database, yielding 20,845 English and Italian records from January 2000 to July 2022.

RESULTS

Six eligible articles were identified following inclusion and exclusion criteria. These studies demonstrated hRSV-positivity proportions ranging from 18% to 41% in pediatric outpatients with respiratory infections. However, data comparability was hindered by diverse diagnostic approaches, data sources, sample populations, and study designs. Notably, hRSV-positivity showed temporal variability, rising from 23.8% (2001-2002) to 40.6% (2019-2020). This trend could stem from evolving epidemiological factors, heightened clinician awareness in hRSV diagnosis, or more sensitive molecular techniques.

CONCLUSION

As the first review of its kind, this study underscores the need for more comprehensive data to inform effective preventive strategies against hRSV-related burdens in pediatric outpatients.

Molecular Epidemiology and Genetic Diversity of Human Respiratory Syncytial Virus in Sicily during Pre- and Post-COVID-19 Surveillance Seasons

Human respiratory syncytial virus (hRSV) is an important pathogen of acute respiratory tract infection of global significance. In this study, we investigated the molecular epidemiology and the genetic variability of hRSV over seven surveillance seasons between 2015 and 2023 in Sicily, Italy. hRSV subgroups co-circulated through every season, although hRSV-B mostly prevailed. After the considerable reduction in the circulation of hRSV due to the widespread implementation of non-pharmaceutical preventive measures during the COVID-19 pandemic, hRSV rapidly re-emerged at a high intensity in 2022-2023. The G gene was sequenced for genotyping and analysis of deduced amino acids. A total of 128 hRSV-A and 179 hRSV-B G gene sequences were obtained. The phylogenetic analysis revealed that the GA2.3.5a (ON1) and GB5.0.5a (BA9) genotypes were responsible for the hRSV epidemics in Sicily.; only one strain belonged to the genotype GB5.0.4a. No differences were observed in the circulating genotypes during pre- and post-pandemic years. Amino acid sequence alignment revealed the continuous evolution of the G gene, with a combination of amino acid changes specifically appearing in 2022-2023. The predicted N-glycosylation sites were relatively conserved in ON1 and BA9 genotype strains. Our findings augment the understanding and prediction of the seasonal evolution of hRSV at the local level and its implication in the monitoring of novel variants worth considering in better design of candidate vaccines.

Incidence of Respiratory Syncytial Virus Infection in Older Adults: Limitations of Current Data

INTRODUCTION

Respiratory syncytial virus (RSV) is an important cause of severe respiratory illness in older adults and adults with respiratory or cardiovascular comorbidities. Published estimates of its incidence and prevalence in adult groups vary widely. This article reviews the potential limitations affecting RSV epidemiology studies and suggests points to consider when evaluating or designing them.

METHODS

Studies reporting the incidence or prevalence of RSV infection in adults in high-income Western countries from 2000 onwards were identified via a rapid literature review. Author-reported limitations were recorded, together with presence of other potential limitations. Data were synthesized narratively, with a focus on factors affecting incidence estimates for symptomatic infection in older adults.

RESULTS

A total of 71 studies met the inclusion criteria, most in populations with medically attended acute respiratory illness (ARI). Only a minority used case definitions and sampling periods tailored specifically to RSV; many used influenza-based or other criteria that are likely to result in RSV cases being missed. The great majority relied solely on polymerase chain reaction (PCR) testing of upper respiratory tract samples, which is likely to miss RSV cases compared with dual site sampling and/or addition of serology. Other common limitations were studying a single season, which has potential for bias due to seasonal variability; failure to stratify results by age, which underestimates the burden of severe disease in older adults; limited generalizability beyond a limited study setting; and absence of measures of uncertainty in the reporting of results.

CONCLUSIONS

A significant proportion of studies are likely to underestimate the incidence of RSV infection in older adults, although the effect size is unclear and there is also potential for overestimation. Well-designed studies, together with increased testing for RSV in patients with ARI in clinical practice, are required to accurately capture both the burden of RSV and the potential public health impact of vaccines.

Respiratory Syncytial Virus in Veneto Region: Analysis of Hospital Discharge Records from 2007 to 2021

Respiratory Syncytial Virus (RSV) is a known cause of acute lower respiratory infections in infants and young children. The present study aims to analyze the temporal trends and characteristics of hospitalization related to RSV in the Veneto region (Italy) in the period between 2007 and 2021. The analysis is performed on all the hospital discharge records (HDRs) of public and accredited private hospitals corresponding to hospitalizations occurring in the Veneto region (Italy). HDRs are considered if they included at least one of the following ICD9-CM codes: 079.6-Respiratory Syncytial Virus (RSV); 466.11-acute bronchiolitis due to RSV; and 480.1-pneumonia due to RSV. Total annual cases, sex, and age-specific rates and trends are evaluated. Overall, an increasing trend in the number of hospitalizations due to RSV was observed between 2007 and 2019, with a slight drop in RSV seasons 2013-2014 and 2014-2015. From March 2020 to September 2021, almost no hospitalization was registered, but in the last quarter of 2021, the number of hospitalizations reached its highest value in the series. Our data confirm the preponderance of RSV hospitalizations in infants and young children, the seasonality of RSV hospitalizations, and acute bronchiolitis as the most frequent diagnosis. Interestingly, the data also show the existence of a significant burden of disease and a non-negligible number of deaths also in older adults. The present study confirms RSV is associated with high rates of hospitalization in infants and sheds light on the burden in the 70+ age group in which a considerable number of deaths was observed, as well as the parallelism with other countries, which is consistent with a wide underdiagnoses issue.

Respiratory Syncytial Virus Prevention through Monoclonal Antibodies: A Cross-Sectional Study on Knowledge, Attitudes, and Practices of Italian Pediatricians

Respiratory Syncytial Virus (RSV) is a leading cause of morbidity and hospitalization in all infants. Many RSV vaccines and monoclonal antibodies (mAb) are currently under development to protect all infants, but to date preventive options are available only for preterms. In this study, we assessed the knowledge, attitudes, and practices towards RSV and the preventive use of mAb in a sample of Italian Pediatricians. An internet survey was administered through an internet discussion group, with a response rate of 4.4% over the potential respondents (No. 389 out of 8842, mean age 40.1 ± 9.1 years). The association of individual factors, knowledge, and risk perception status with the attitude towards mAb was initially inquired by means of a chi squared test, and all variables associated with mAb with p < 0.05 were included in a multivariable model calculating correspondent adjusted Odds Ratio (aOR) with 95% confidence intervals (95%CI). Of the participants, 41.9% had managed RSV cases in the previous 5 years, 34.4% had diagnosed RSV cases, and 32.6% required a subsequent hospitalization. However, only 14.4% had previously required mAb as immunoprophylaxis for RSV. Knowledge status was substantially inappropriate (actual estimate 54.0% ± 14.2, potential range 0-100), while the majority of participants acknowledged RSV as a substantial health threat for all infants (84.8%). In multivariable analysis, all these factors were characterized as positive effectors for having prescribed mAb (aOR 6.560, 95%CI 2.904-14.822 for higher knowledge score; aOR 6.579, 95%CI 2.919-14.827 for having a hospital background, and a OR 13.440, 95%CI 3.989; 45.287 for living in Italian Major Islands). In other words, reporting less knowledge gaps, having worked in settings with a higher risk of interaction with more severe cases, and being from Italian Major Islands, were identified as positive effectors for a higher reliance on mAb. However, the significant extent of knowledge gaps highlights the importance of appropriate medical education on RSV, its potential health consequences, and the investigational preventive interventions.

Infodemiology of RSV in Italy (2017-2022): An Alternative Option for the Surveillance of Incident Cases in Pediatric Age?

The aim of this study was to evaluate whether or not online queries for Respiratory Syncytial Virus (RSV) retrieved by means of Google Trends™ and the Italian Wikipedia analysis program mirror the occurrence of influenza-like illnesses (ILI), as reported by the Italian Influenza Surveillance network (InfluNet). Estimated rates for ILI in the general population and in the age groups 0−4 years and 5−14 years were obtained for the influenza seasons 2017−2018 to 2020−2021. Similarly, a weekly fraction of online searches was retrieved for a series of terms associated with Respiratory Syncytial Virus. Next, trends for daily visualization of Italian Wikipedia Pages for Human Respiratory Syncytial Virus, Pneumonia, Bronchiolitis, Influenza, and Respiratory Failure were similarly retrieved. The correlation of all search terms with ILI was analyzed by means of Spearman’s rank correlation analysis. Among search terms associated with the clinical diagnosis of Respiratory Syncytial Virus infections, the occurrence of ILI was highly correlated only with Bronchiolitis in the age group 0−4 years (β 0.210, p = 0.028), while more generic search terms, such as Bronchitis, fever, influenza, and Pneumonia, were identified as effective predictors of ILI, in general and by age groups. In a regression analysis modeled with ILIs as the outcome variable, daily visualizations for the Wikipedia pages on Bronchiolitis were identified as negative predictors for ILI in general (β = −0.152, p = 0.032), ILI in age group 0−4 years (β = −0.264, p = 0.001) and 5−14 years (β = −0.202, p = 0.006), while Influenza was characterized as a positive effector for ILIs in the age group 5−14 years (β = 0.245, p = 0.001). Interestingly, not only were the search terms extensively correlated with one another, but all of them were also characterized by autocorrelation through a Durbin-Watson test (all estimates DW < 2.0) In summary, our study identified a complicated pattern of data visualization as no clear association between rates of ILI in pediatric age group 0−4 and 5 to 14 years was actually found. Finally, our data stress that the infodemiology option may be quite problematic for assessing the time trend of RSV infections in Italy until more appropriate reporting will be made available, by sharing estimates of Lower Respiratory Tract Infections, and through a more accurate characterization of younger age groups.

Rate of Hospitalizations and Mortality of Respiratory Syncytial Virus Infection Compared to Influenza in Older People: A Systematic Review and Meta-Analysis

Respiratory Syncytial Virus (RSV) is commonly regarded as an infection typical of children, but increasing literature is showing its importance in older people. Since the data regarding the impact of RSV are still limited for older people, the aim of this systematic review and meta-analysis is to compare the rate of hospitalization and mortality between RSV and influenza in this population. A systematic literature search until 15 June 2022 was done across several databases and including studies reporting incidence rate and cumulative incidence of hospitalization and mortality in RSV and influenza affecting older people. Among 2295 records initially screened, 16 studies including 762,084 older participants were included. Compared to older patients having influenza, patients with RSV did not show any significant different risk in hospitalization (either cumulative or incidence rate). Similar results were evident for mortality. The quality of the studies was in general good. In conclusion, our systematic review and meta-analysis showed that the rate of hospitalization and mortality was similar between RSV and influenza in older adults, suggesting the importance of vaccination for RSV in older people for preventing negative outcomes, such as mortality and hospitalization.

RSV disease in infants and young children: Can we see a brighter future?

Respiratory syncytial virus (RSV) is a highly contagious seasonal virus and the leading cause of Lower Respiratory Tract Infections (LRTI), including pneumonia and bronchiolitis in children. RSV-related LRTI cause approximately 3 million hospitalizations and 120,000 deaths annually among children <5 years of age. The majority of the burden of RSV occurs in previously healthy infants. Only a monoclonal antibody (mAb) has been approved against RSV infections in a restricted group, leaving an urgent unmet need for a large number of children potentially benefiting from preventive measures. Approaches under development include maternal vaccines to protect newborns, extended half-life monoclonal antibodies to provide rapid long-lasting protection, and pediatric vaccines. RSV has been identified as a major global priority but a solution to tackle this unmet need for all children has yet to be implemented. New technologies represent the avenue for effectively addressing the leading-cause of hospitalization in children <1 years old.

Respiratory Syncytial Virus in Pregnant Women: Systematic Review and Meta-Analysis

Human Respiratory Syncytial Virus (RSV) is a highly contagious viral pathogen. In infants, it is usually listed among the main causes of medical referrals and hospitalizations, particularly among newborns. While waiting for the results of early randomized controlled trials on maternal vaccination against RSV, the present systematic review and meta-analysis aimed to collect available evidence on maternal RSV infections. According to the PRISMA statement, Pubmed, Embase, and pre-print archive medRxiv.og were searched for eligible studies published up to 1 April 2022. Raw data included the incidence of RSV infection among sampled pregnant women, and the occurrence of complications. Data were then pooled in a random-effects model. Heterogeneity was assessed using the I2 measure, while reporting bias was assessed by means of funnel plots and regression analysis. A total of 5 studies for 282,918 pregnancies were retrieved, with a pooled prevalence of 0.2 per 100 pregnancies and 2.5 per 100 pregnancies with respiratory tract infections. Neither maternal deaths nor miscarriages were reported. Even though detailed data were available only for 6309 pregnancies and 33 RSV cases, infant outcomes such as low birth weight and preterm delivery were rare (in both cases 0.04%), but up to 9.1% in cases where RSV diagnosis was confirmed. No substantially increased risk for preterm delivery (RR 1.395; 95%CI 0.566 to 3.434) and giving birth to a low-birth-weight infant (RR 0.509; 95%CI 0.134 to 1.924) was eventually identified. Conclusions. Although RSV is uncommonly detected among pregnant women, incident cases were associated with a relatively high share of complications. However, heterogeneous design and the quality of retrieved reports stress the need for specifically designed studies.