Defining the seasonality of respiratory syncytial virus around the world: National and subnational surveillance data from 12 countries

Respiratory syncytial virus: challenges in diagnosis and impact on the elderly: Recommendations from a multidisciplinary panel

Respiratory syncytial virus (RSV) is an important cause of respiratory illness. While most attention is paid to childhood infection, the RSV burden in adults ≥60 y should also be considered. In Brazil, this is generally underrecognized, where greater focus is toward other respiratory pathogens. This article presents insights from a multidisciplinary panel gathered to review epidemiologic data and current diagnostic approaches to RSV in Brazil (and their limitations) and develop communication strategies to improve knowledge and awareness. National surveillance data indicate a steady increase in cases of RSV-related severe acute respiratory illness (RSV-SARI) in those aged ≥60 y in recent years, with high fatality rates (>30%). Routine RSV testing in older individuals with respiratory symptoms is relatively low. Educational activities targeted toward health-care professionals and the general public are critical to raising awareness of the importance of RSV in older individuals, particularly as protective vaccines are now available.

Burden of respiratory syncytial virus (RSV) infection in Germany: a systematic review

BACKGROUND

Respiratory syncytial virus (RSV) is a major cause of acute lower respiratory infection and hospitalizations among infants, young children, and the elderly. This systematic literature review aimed to summarize the epidemiological and economic burden estimates of RSV infection at any age in Germany.

METHODS

We conducted a systematic literature search to identify full-text articles published from 2003 to 2023 and reporting data on the epidemiological or economic burden of RSV in Germany. Based on pre-specified eligibility criteria, data on incidence, rates of hospital and intensive care unit (ICU) admission, clinical manifestation, underlying conditions, seasonality, health care resource use and costs were extracted.

RESULTS

After screening 315 full-text articles, we included 42 articles in the review. The characteristics of the included studies were heterogenous regarding study population, setting, age groups and RSV-related outcome measures. The most frequently reported epidemiological outcome measures were RSV detection rate (n = 33), followed by clinical manifestation (n = 19), seasonality (n = 18), and underlying conditions of RSV infection (n = 13). RSV detection rates were reported across heterogenous study populations, ranging from 5.2 to 55.4% in pediatric inpatient cases and from 2.9 to 14% in adult inpatient cases. All articles that reported RSV detection rates across several age groups demonstrated the highest burden in infants and young children. Few articles reported RSV-related outcome measures distinctively for the outpatient setting. Health care resource use, such as hospital length of stay, ICU admission rate and treatment of patients with RSV infection were described in 23 articles, of which only one study quantified associated costs from 1999 to 2003 for children ≤ 3 years. In-hospital ICU admission rates varied between 3.6 and 45%, depending on population characteristics as age and underlying conditions.

CONCLUSIONS

This systematic review revealed that RSV imposes substantial disease burden in infants, young children, and the elderly in Germany, whereby infants are particularly affected. To date, there has been limited exploration of the impact of RSV infection on healthy children or the elderly in Germany. Given their notably high reported burden in studies, the medical and economic RSV burden in these groups should move more into focus.

Genomic Evolution and Surveillance of Respiratory Syncytial Virus during the 2023-2024 Season

Respiratory syncytial virus (RSV) is a significant cause of morbidity, particularly in infants. This study describes RSV genomic diversity and disease outcomes during the 2023-2024 season in the Johns Hopkins Hospital System (JHHS). Between August and December 2023, 406 patient samples were sequenced, showing that RSV-B GB5.0.5a was the dominant genotype detected. RSV-A genotype GA2.3.5 was detected less frequently. Metadata analysis of patient data revealed that, although RSV-B was more commonly detected, patients with RSV-A infections were more frequently hospitalized. Analysis of both the G- and F-genes revealed multiple amino acid substitutions in both RSV-A and RSV-B, with some positions within the F-protein that could be associated with evasion of antibody responses. Phylogenetic analysis revealed the genetic diversity of circulating GB5.0.5a and GA2.3.5 genotypes. This study serves as an important baseline for genomic surveillance of RSV within the JHHS and will assist in characterizing the impact of the newly approved RSV vaccines on RSV genomic evolution and the emergence of escape mutations.

Variability in the Timing of Respiratory Syncytial Virus Epidemics in Guatemala, 2008-2018

BACKGROUND

The description of local seasonality patterns in respiratory syncytial virus (RSV) incidence is important to guide the timing of administration of RSV immunization products.

METHODS

We characterized RSV seasonality in Guatemala using the moving epidemic method (MEM) with absolute counts of RSV-associated acute respiratory infections (ARI) from hospital surveillance in Santa Rosa and Quetzaltenango departments of Guatemala.

RESULTS

From Week 17 of 2008 through Week 16 of 2018, 8487 ARI cases tested positive for RSV by rRT-PCR. Season onsets varied up to 5 months; early seasons starting in late May to early August and finishing in September to November were most common, but late seasons starting in October to November and finishing in March to April were also observed. Both epidemic patterns had similar durations ranging from 4 to 6 months. Epidemic thresholds (the levels of virus activity that signal the onset and end of a seasonal epidemic) calculated prospectively using previous seasons' data captured between 70% and 99% of annual RSV detections. Onset weeks differed by 2-10 weeks, and offset weeks differed by 2-16 weeks between the two surveillance sites.

CONCLUSIONS

Variability in the timing of seasonal RSV epidemics in Guatemala demonstrates the difficulty in precisely predicting the timing of seasonal RSV epidemics based on onset weeks from past seasons and suggests that maximal reduction in RSV disease burden would be achieved through year-round vaccination and immunoprophylaxis administration to at-risk infants.

Global analysis of respiratory viral circulation and timing of epidemics in the pre-COVID-19 and COVID-19 pandemic eras, based on data from the Global Influenza Surveillance and Response System (GISRS)

OBJECTIVES

The COVID-19 pandemic significantly changed respiratory viruses' epidemiology due to non-pharmaceutical interventions and possible viral interactions. This study investigates whether the circulation patterns of respiratory viruses have returned to pre-pandemic norms by comparing their peak timing and duration during the first three SARS-CoV-2 seasons to pre-pandemic times.

METHODS

Global Influenza Surveillance and Response System data from 194 countries (2014-2023) was analyzed for epidemic peak timing and duration, focusing on pre-pandemic and pandemic periods across both hemispheres and the intertropical belt. The analysis was restricted to countries meeting specific data thresholds to ensure robustness.

RESULTS

In 2022/2023, the northern hemisphere experienced earlier influenza and respiratory syncytial virus (RSV) peaks by 1.9 months (P <0.001). The duration of influenza epidemics increased by 2.2 weeks (P <0.001), with RSV showing a similar trend. The southern hemisphere's influenza peak shift was not significant (P = 0.437). Intertropical regions presented no substantial change in peak timing but experienced a significant reduction in the duration for human metapneumovirus and adenovirus (7.2 and 6.5 weeks shorter, respectively, P <0.001).

CONCLUSIONS

The pandemic altered the typical patterns of influenza and RSV, with earlier peaks in 2022 in temperate areas. These findings highlight the importance of robust surveillance data to inform public health strategies on evolving viral dynamics in the years to come.

Trends in RSV testing patterns among infants presenting with bronchiolitis: Results from four United States health systems, 2015-2023

BACKGROUND

Bronchiolitis due to respiratory syncytial virus (RSV) is the leading cause of hospitalization among American infants. The overall burden of RSV among infants has been historically under-estimated due to variable testing practices, particularly in the outpatient setting. Universal masking and social distancing implemented during the coronavirus disease 2019 (COVID-19) pandemic altered RSV seasonality, however potential consequences on RSV testing practices across different healthcare settings and sociodemographic groups have not been described. Variable testing practices could also affect accurate assessment of the effects of two recently approved RSV preventative agents targeting infants.

METHODS

Utilizing real-time clinical and viral surveillance, we examined RSV testing practices among infants with bronchiolitis within four United States healthcare systems across different healthcare settings and sociodemographic groups pre- and post-COVID-19.

RESULTS

RSV testing among infants with bronchiolitis increased since 2015 within each healthcare system across all healthcare settings and sociodemographic groups, with a more dramatic increase since the COVID-19 pandemic. Outpatient testing remained disproportionately low compared to hospital-based testing, although there were no major differences in testing frequency among sociodemographic groups in either setting.

CONCLUSIONS

Although RSV testing increased among infants with bronchiolitis, relatively low outpatient testing rates remain a key barrier to accurate RSV surveillance.

Respiratory syncytial virus seasonality, transmission zones, and implications for seasonal prevention strategy in China: a systematic analysis

BACKGROUND

Respiratory syncytial virus (RSV) represents a substantial global health challenge, with a disproportionately high disease burden in low-income and middle-income countries. RSV exhibits seasonality in most areas globally, and a comprehensive understanding of within-country variations in RSV seasonality could help to define the timing of RSV immunisation programmes. This study focused on China, and aimed to describe the geographical distribution of RSV seasonality, identify distinct RSV transmission zones, and evaluate the potential suitability of a seasonal RSV prevention strategy.

METHODS

We did a systematic analysis of RSV seasonality in China, with use of data on RSV activity extracted from a systematic review of studies published on Embase, MEDLINE, Web of Science, China National Knowledge Infrastructure, Wanfang Data, Chongqing VIP Information, and SinoMed, from database inception until May 5, 2023. We included studies of any design in China reporting at least 25 RSV cases, which aggregated RSV case number by calendar month or week at the province level, and with data covering at least 12 consecutive months before the year 2020 (prior to the COVID-19 pandemic). Studies that used only serology for RSV testing were excluded. We also included weekly data on RSV activity from open-access online databases of the Taiwan National Infection Disease Statistics System and Hong Kong Centre for Health Protection, applying the same eligiblity requirements. Across all datasets, we excluded data on RSV activity from Jan 1, 2020, onwards. We estimated RSV seasonal epidemic onset and duration using the annual average percentage (AAP) approach, and summarised seasonality at the provincial level. We used Pearson's partial correlation analysis to assess the correlation between RSV season duration and the latitude and longitude of the individual provinces. To define transmission zones, we used two independent approaches, an infant-passive-immunisation-driven approach (the moving interval approach, 6-month interval) and a data-driven approach (k-means), to identify groups of provinces with similar RSV seasonality. The systematic review was registered on PROSPERO, CRD42022376993.

FINDINGS

A total of 157 studies were included along with the two online datasets, reporting data on 194 596 RSV cases over 442 study-years (covering the period from Jan 1, 1993 to Dec 31, 2019), from 52 sites in 23 provinces. Among 21 provinces with sufficient data (≥100 reported cases), the median duration of RSV seasonal epidemics was 4·6 months (IQR 4·1-5·4), with a significant latitudinal gradient (r=-0·69, p<0·0007), in that provinces on or near the Tropic of Cancer had the longest epidemic duration. We found no correlation between longitude and epidemic duration (r=-0·15, p=0·53). 15 (71%) of 21 provinces had RSV epidemics from November to March. 13 (62%) of 21 provinces had clear RSV seasonality (epidemic duration ≤5 months). The moving interval approach categorised the 21 provinces into four RSV transmission zones. The first zone, consisting of five provinces (Fujian, Guangdong, Hong Kong, Taiwan, and Yunnan), was assessed as unsuitable for seasonal RSV immunisation strategies; the other three zones were considered suitable for seasonal RSV immunisation strategies with the optimal start month varying between September (Hebei), October (Anhui, Chongqing, Henan, Hubei, Jiangsu, Shaanxi, Shandong, Shanghai, Sichuan, and Xinjiang), and November (Beijing, Gansu, Guizhou, Hunan, and Zhejiang). The k-means approach identified two RSV transmission zones, primarily differentiated by whether the province was on or near the Tropic of Cancer (Fujian, Guangdong, Hong Kong, Taiwan, Yunan, and Hunan) or not (the remaining 15 provinces).

INTERPRETATION

Although substantial variations in RSV seasonality were observed across provinces of China, our study identified distinct transmission zones with shared RSV circulating patterns. These findings could have important implications for decision making on RSV passive immunisation strategy. Furthermore, the methodological framework in this study for defining RSV seasons and identifying RSV transmission zones is potentially applicable to other countries or regions.

FUNDING

Nanjing Medical University.

TRANSLATION

For the Chinese translation of the abstract see Supplementary Materials section.

Factors associated with severe respiratory syncytial virus infection among hospitalized children in Thammasat University Hospital

Background

Respiratory syncytial virus (RSV) is one of the most significant respiratory pathogens that causes acute lower respiratory tract infections (LRTI) early in life. Most children have a history of RSV infection within 24 months of age, and recurrent infections are common throughout life.

Methods

Children under five years of age were identified through a review of medical records with a diagnosis of RSV-LRTI between 2016 and 2020. Severe RSV-LRTI was defined as a prolonged length of stay (> 7 days), admission to the intensive care unit, need for mechanical ventilation, non-invasive positive pressure ventilation, or in-hospital mortality. Factors associated with severe RSV-LRTI were investigated using univariate and multivariate analyses.

Results

During the study period, 620 patients were diagnosed with RSV-LRTI and 249 (40.16%) patients had severe RSV-LRTI. In the multivariable logistic regression analysis, the factors for severe RSV-LRTI were being under 3 months (aOR 2.18 CI 1.39-3.43, p0.001), cardiovascular disease (aOR 3.55 CI 1.56-8.06, p0.002), gastrointestinal disease (aOR 5.91 CI 1.90-18.46, p0.002), genetic disease (aOR 7.33 CI 1.43-37.54, p0.017), and pulmonary disease (aOR 9.50, CI 4.56-19.80, p<0.001). Additionally, the presence of ≥ 2 co-morbidities (aOR 6.23 CI 2.81-14.81, p<0.016), experiencing illness for more than 5 days (aOR 3.33 CI 2.19-5.06, p<0.001), co-detection of influenza (aOR 8.62 CI 1.49-38.21, p0.015), and nosocomial RSV infection (aOR 9.13 CI 1.98-41.30, p0.012), markedly increased the risk of severe RSV-LTRI. The severe RSV-LRTI group demonstrated higher hospitalization expenses (median, US $720.77 vs $278.00, respectively; p<0.001), and three infants died in-hospital.

Conclusion

Children at high risk for RSV-LRTI due to underlying genetic and gastrointestinal diseases are at an increased risk for severe RSV-LRTI. Further studies to determine the cost-effectiveness of RSV immunization in these potential co-morbidities should be initiated to prioritize RSV immunization, especially in resource-constrained regions with limited availability of nirsevimab.

Geographic Progression of Infant Respiratory Syncytial Virus Associated Bronchiolitis Across the United States Before and Since the Onset of COVID-19: Results From Four Health Systems, 2015-2023

BACKGROUND

Respiratory syncytial virus (RSV) is a substantial cause of infant morbidity and mortality due to seasonal peaks of bronchiolitis across the United States. Clinical and viral surveillance plays a pivotal role in helping hospital systems prepare for expected surges in RSV bronchiolitis. Existing surveillance efforts have shown a geographic pattern of RSV positivity across the United States, with cases typically starting in the southeast and spreading north and west. Public health measures implemented due to the COVID-19 pandemic disrupted viral transmission across the nation and altered the expected seasonality of RSV. The impact of these changes on the geographic progression of infant RSV bronchiolitis across the United States has not been described.

METHODS

Here, we used clinical and viral surveillance data from four health care systems located in different regions of the United States to describe the geographic progression of infant RSV bronchiolitis across the country from 2015 to 2023.

RESULTS

Prior to widespread circulation of SARS-CoV-2, infant RSV bronchiolitis followed an established geographic pattern associated with seasonal epidemics originating in Florida and spreading north (North Carolina and New York) and later westward (Nevada). Although public health and social measures implemented during the COVID-19 pandemic disrupted the seasonality of RSV disease, infant RSV bronchiolitis epidemics progressed across the nation in a pattern identical to the prepandemic era.

CONCLUSIONS

Our findings highlight the importance of ongoing clinical and viral surveillance to optimally track the onset of RSV epidemics and allow health care systems to prepare for expected RSV bronchiolitis surges.

Change in Age profile of Respiratory Syncytial Virus disease over the course of annual epidemics: a multi-national study

OBJECTIVES

We aimed to study whether the percentwise age distribution of RSV cases changes over time during annual epidemics.

METHODS

We used surveillance data (2008-2019) from the Netherlands, Lyon (France), Portugal, Singapore, Ecuador, South Africa, and New Zealand. In each country, every season was divided into "epidemic quarters", i.e. periods corresponding to each quartile of RSV cases. Multinomial logistic regression models were fitted to evaluate whether the likelihood of RSV cases being aged <1 or ≥5 years (vs. 1 to <5) changed over time within a season.

RESULTS

In all countries, RSV cases were significantly more likely to be aged <1 year in the 4th vs. 1st epidemic quarter; the relative risk ratio [RRR] ranged between 1.35 and 2.56. Likewise, RSV cases were significantly more likely to be aged ≥5 years in the 4th vs. 1st epidemic quarter (except in Singapore); the RRR ranged from 1.75 to 6.70. The results did not change when stratifying by level of care or moving the lower cut-off to 6 months.

CONCLUSIONS

The age profile of RSV cases shifts within a season, with infants and adolescents, adults, and the elderly constituting a higher proportion of cases in the later phases of annual epidemics. These findings may have implications for RSV prevention policies with newly approved vaccines.

Global Seasonal Activities of Respiratory Syncytial Virus Before the Coronavirus Disease 2019 Pandemic: A Systematic Review

Varied seasonal patterns of respiratory syncytial virus (RSV) have been reported worldwide. We conducted a systematic review on articles identified in PubMed reporting RSV seasonality based on data collected before 1 January 2020. RSV seasonal patterns were examined by geographic location, calendar month, analytic method, and meteorological factors including temperature and absolute humidity. Correlation and regression analyses were conducted to explore the relationship between RSV seasonality and study methods and characteristics of study locations. RSV seasons were reported in 209 articles published in 1973-2023 for 317 locations in 77 countries. Regular RSV seasons were similarly reported in countries in temperate regions, with highly variable seasons identified in subtropical and tropical countries. Longer durations of RSV seasons were associated with a higher daily average mean temperature and daily average mean absolute humidity. The global seasonal patterns of RSV provided important information for optimizing interventions against RSV infection.

Quantification of multiple respiratory viruses in wastewater in the Kathmandu Valley, Nepal: Potential implications of wastewater-based epidemiology for community disease surveillance in developing countries

Despite being the major cause of death, clinical surveillance of respiratory viruses at the community level is very passive, especially in developing countries. This study focused on the surveillance of three respiratory viruses [severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), influenza A virus (IFV-A), and respiratory syncytial virus (RSV)] in the Kathmandu Valley, Nepal, by implication of wastewater-based epidemiology (WBE). Fifty-one untreated wastewater samples were from two wastewater treatment plants (WWTPs) between April and October 2022. Among eight combinations of the pre-evaluated methods, the combination of concentration by simple centrifugation, pretreatment by DNA/RNA Shield (Zymo Research), and extraction by the QIAamp Viral RNA Mini Kit (QIAGEN) showed the best performance for detecting respiratory viruses. Using this method with a one-step reverse transcription-quantitative polymerase chain reaction (RT-qPCR), SARS-CoV-2 RNA was successfully detected from both WWTPs (positive ratio, 100 % and 81 %) at concentrations of 5.6 ± 0.6 log10 copies/L from each WWTP. Forty-six SARS-CoV-2 RNA-positive samples were further tested for three mutation site-specific one-step RT-qPCR (L452R, T478K, and E484A/G339D), where G339D/E484A mutations were frequently detected in both WWTPs (96 %). IFV-A RNA was more frequently detected in WWTP A (84 %) compared to WWTP B (38 %). RSV RNA was also detected in both WWTPs (28 % and 8 %, respectively). This is the first study on detecting IFV-A and RSV in wastewater in Nepal, showing the applicability and importance of WBE for respiratory viruses in developing countries where clinical data are lacking.

Epidemiology of respiratory syncytial virus in a large pediatric hospital in Central Italy and development of a forecasting model to predict the seasonal peak

BACKGROUND

Respiratory Syncytial Virus (RSV) is responsible for the majority of acute lower respiratory infections in infants and can affect also older age groups. Restrictions linked to the emergence of the SARS-CoV-2 pandemic and their subsequent lifting caused a change in the dynamics of RSV circulation. It is therefore fundamental to monitor RSV seasonal trends and to be able to predict its seasonal peak to be prepared to the next RSV epidemics.

METHODS

We performed a retrospective descriptive study on laboratory-confirmed RSV infections from Bambino Gesù Children's Hospital in Rome from 1st January 2018 to 31st December 2022. Data on RSV-positive respiratory samples (n = 3,536) and RSV-confirmed hospitalizations (n = 1,895) on patients aged 0-18 years were analyzed. In addition to this, a SARIMA (Seasonal AutoRegressive Integrated Moving Average) forecasting model was developed to predict the next peak of RSV.

RESULTS

Findings show that, after the 2020 SARS-CoV-2 pandemic season, where RSV circulation was almost absent, RSV infections presented with an increased and anticipated peak compared to pre-pandemic seasons. While mostly targeting infants below 1 year of age, there was a proportional increase in RSV infections and hospitalizations in older age groups in the post-pandemic period. A forecasting model built using RSV weekly data from 2018 to 2022 predicted the RSV peaks of 2023, showing a reasonable level of accuracy (MAPE 33%). Additional analysis indicated that the peak of RSV cases is expected to be reached after 4-5 weeks from case doubling.

CONCLUSION

Our study provides epidemiological evidence on the dynamics of RSV circulation before and after the COVID-19 pandemic. Our findings highlight the potential of combining surveillance and forecasting to promote preparedness for the next RSV epidemics.

The disease burden of respiratory syncytial virus in older adults

PURPOSE OF REVIEW

To highlight the respiratory syncytial virus (RSV) disease burden and the current developments and challenges in RSV prevention for older adults ≥60 years through analysis of RSV epidemiology and the effectiveness of emerging vaccines.

RECENT FINDINGS

In industrialized countries, RSV incidence rates and hospitalization rates among older adults are estimated to be 600.7 cases per 100 000 person-years and 157 hospitalizations per 100 000 person-years, respectively. Yet, accurately determining RSV morbidity and mortality in older adults is challenging, thus resulting in substantially under-estimating the disease burden. The in-hospital fatality rates vary substantially with age and geographies, and can be as high as 9.1% in developing countries. Two promising RSV vaccines for the elderly have been approved, demonstrating efficacies of up to 94.1%, signifying considerable advancement in RSV prevention. However, concerns over potential side effects remain.

SUMMARY

RSV is associated with a significant burden in older adults. While the landscape of RSV prevention in older adults is promising with the licensure of vaccines from two companies, current trial data underscore the need for additional studies. Addressing the real-world effectiveness of these vaccines, understanding potential rare side effects, and ensuring broad inclusivity in future trials are crucial steps to maximize their potential benefits.

Predictors of severity and prolonged hospital stay of viral acute respiratory infections (ARI) among children under five years in Burkina Faso, 2016-2019

BACKGROUND

Viruses are the leading etiology of acute respiratory infections (ARI) in children. However, there is limited knowledge on drivers of severe acute respiratory infection (SARI) cases involving viruses. We aimed to identify factors associated with severity and prolonged hospitalization of viral SARI among children < 5 years in Burkina Faso.

METHODS

Data were collected from four SARI sentinel surveillance sites during October 2016 through April 2019. A SARI case was a child < 5 years with an acute respiratory infection with history of fever or measured fever ≥ 38 °C and cough with onset within the last ten days, requiring hospitalization. Very severe ARI cases required intensive care or had at least one danger sign. Oropharyngeal/nasopharyngeal specimens were collected and analyzed by multiplex real-time reverse-transcription polymerase chain reaction (rRT-PCR) using FTD-33 Kit. For this analysis, we included only SARI cases with rRT-PCR positive test results for at least one respiratory virus. We used simple and multilevel logistic regression models to assess factors associated with very severe viral ARI and viral SARI with prolonged hospitalization.

RESULTS

Overall, 1159 viral SARI cases were included in the analysis after excluding exclusively bacterial SARI cases (n = 273)very severe viral ARI cases were common among children living in urban areas (AdjOR = 1.3; 95% CI: 1.1-1.6), those < 3 months old (AdjOR = 1.5; 95% CI: 1.1-2.3), and those coinfected with Klebsiella pneumoniae (AdjOR = 1.9; 95% CI: 1.2-2.2). Malnutrition (AdjOR = 2.2; 95% CI: 1.1-4.2), hospitalization during the rainy season (AdjOR = 1.71; 95% CI: 1.2-2.5), and infection with human CoronavirusOC43 (AdjOR = 3; 95% CI: 1.2-8) were significantly associated with prolonged length of hospital stay (> 7 days).

CONCLUSION

Younger age, malnutrition, codetection of Klebsiella pneumoniae, and illness during the rainy season were associated with very severe cases and prolonged hospitalization of SARI involving viruses in children under five years. These findings emphasize the need for preventive actions targeting these factors in young children.

Changes in Prevalence and Seasonality of Pathogens Identified in Acute Respiratory Tract Infections in Hospitalised Individuals in Rural and Urban Settings in South Africa; 2018-2022

Severe acute respiratory tract infections (SARIs) has been well described in South Africa with seasonal patterns described for influenza and respiratory syncytial virus (RSV), while others occur year-round (rhinovirus and adenovirus). This prospective syndromic hospital-based surveillance study describes the prevalence and impact of public interventions on the seasonality of other respiratory pathogens during the coronavirus disease-19 (COVID-19) pandemic. This occurred from August 2018 to April 2022, with 2595 patients who met the SARS case definition and 442 controls, from three sentinel urban and rural hospital sites in South Africa. Naso/oro-pharyngeal (NP/OP) swabs were tested using the FastTrack Diagnostics® Respiratory pathogens 33 (RUO) kit. Descriptive statistics, odds ratios, and univariate/multivariate analyses were used. Rhinovirus (14.80%, 228/1540) and Streptococcus pneumoniae (28.50%, 439/1540) were most frequently detected in NP/OP swabs and in children <1 years old (35%, 648/1876). Among others, pathogens associated with SARI cases causing disease were influenza A&B, HRV, RSV, hCoV 229e, Haemophilus influenzae, Staphylococcus aureus, and Streptococcus pneumoniae. Pre-COVID-19, seasonal trends of these pathogens correlated with previous years, with RSV and influenza A seasons only resuming after the national lockdown (2021). It is evident that stringent lockdown conditions have severe impacts on the prevalence of respiratory tract infections.

Resurgence of human respiratory syncytial virus during COVID-19 pandemic in Southern Brazil

Respiratory Syncytial Virus (RSV) is an important cause of respiratory infection in humans. Severe cases are common in children ≤2 years old, immunocompromised individuals, and the elderly. In 2020, RSV infection reduced in Rio Grande do Sul (RS), southern Brazil; however, in 2021 resurgence of RSV was observed. This study analyzed epidemiological and genetic features of RSV infection cases reported in 2021 in RS. Nasopharyngeal samples collected from individuals with respiratory infection negative for SARS-CoV-2, Influenza A and B viruses were assessed for the presence of RSV by real time RT-qPCR. RSV-A and RSV-B genomic sequencing and phylogenetic reconstructions were performed for genotyping and clade characterization. Among 21,035 respiratory samples analyzed, 2,947 were positive for RSV, 947 of which were hospitalized patients. Positive cases were detected year-round, with the highest number in June-July (winter). Children <1 year comprised 56.28% (n = 533) of the hospitalized patients infected with RSV, whereas 14.46% (n = 137) were individuals >60 years. Of a total of 361 deaths, 14.68% (n = 53) were RSV positive, mostly patients >60 years old (73.58%, n = 39). Chronic kidney disease, cardiopathy, Down syndrome and neurological diseases were associated with RSV infection. RSV-A was identified in 58.5% (n = 117/200) of the patients, and RSV-B in 41.5% (n = 83/200). Of 95 RSV genomes recovered from SARI cases, 66 were RSV-A GA.2.3.5 genotype, while 29 were RSV-B GB.5.0.5a genotype. This study provides epidemiological and molecular data on RSV cases in RS during the COVID-19 pandemic and highlights that investigation of different respiratory viruses is essential for decision-making and disease prevention and control measures.

Epidemiology and Disease Burden of Respiratory Syncytial Virus Infection in Adults

Respiratory syncytial virus (RSV) constitutes a significant cause of respiratory illness and mortality among older adults, a demographic that is expanding with considerable impact on healthcare systems worldwide. The actual burden of RSV in this population may still be underestimated, owing to factors such as low awareness and suboptimal diagnostic sensitivity in adults, the lack of robust RSV surveillance systems, and the infrequent use of diagnostic testing. Recent advancements in respiratory virus detection have spurred further exploration into appropriate preventive and therapeutic strategies. The recent approval of two vaccines highlights the critical need for the precise estimation of the RSV disease burden to optimize the effectiveness and cost-efficiency of immunization programs. This narrative review aimed to summarize the existing knowledge of the RSV burden in adults with a particular focus on older adults, incorporating data from Korea. Overall, current estimates indicate that the annual RSV attack rate in the general adult population ranges from 1 - 7%, increasing to approximately 4 - 10% among elderly and high-risk groups. The in-hospital mortality rate can be estimated to be around 7 - 10%, rising up to 40% among intensive care unit-admitted patients. To elucidate RSV's disease burden, further continuing research, including population-based studies, is necessary.

Respiratory Syncytial Virus European Laboratory Network 2022 Survey: Need for Harmonization and Enhanced Molecular Surveillance

Respiratory syncytial virus (RSV) is a common pathogen causing mostly cold-like symptoms, but in very young infants and elderly individuals it can lead to severe disease and even death. There are currently promising developments both in vaccine development and in therapeutics that are expected to be approved soon. To get an impression within European countries of the laboratory diagnostics and surveillance activities, in anticipation of these developments, we queried the members of the European Respiratory Syncytial Virus Laboratory Network (RSV-LabNet, under the umbrella of the PROMISE project) via an online survey. The answers from the consortium members showed scattered monitoring and the application of a broad array of techniques in the laboratories. A majority of the members expressed strong interest in harmonization and collaboration for setting up surveillance programs and the need for sharing laboratory protocols. The additional value of RSV whole-genome sequencing is broadly appreciated, but implementation requires further development and closer collaboration. The RSV-LabNet can have an important responsibility in establishing contacts and exchange of expertise and providing a platform for communication to advance diagnostics, preparedness, and surveillance.

Burden of Respiratory Syncytial Virus-Associated Acute Respiratory Infections During Pregnancy

BACKGROUND

With the licensure of maternal respiratory syncytial virus (RSV) vaccines in Europe and the United States, data are needed to better characterize the burden of RSV-associated acute respiratory infections (ARI) in pregnancy. The current study aimed to determine among pregnant individuals the proportion of ARI testing positive for RSV and the RSV incidence rate, RSV-associated hospitalizations, deaths, and perinatal outcomes.

METHODS

We conducted a systematic review, following PRISMA 2020 guidelines, using 5 databases (Medline, Embase, Global Health, Web of Science, and Global Index Medicus), and including additional unpublished data. Pregnant individuals with ARI who had respiratory samples tested for RSV were included. We used a random-effects meta-analysis to generate overall proportions and rate estimates across studies.

RESULTS

Eleven studies with pregnant individuals recruited between 2010 and 2022 were identified, most of which recruited pregnant individuals in community, inpatient and outpatient settings. Among 8126 pregnant individuals, the proportion with ARI that tested positive for RSV ranged from 0.9% to 10.7%, with a meta-estimate of 3.4% (95% confidence interval [CI], 1.9%-54%). The pooled incidence rate of RSV among pregnant individuals was 26.0 (95% CI, 15.8-36.2) per 1000 person-years. RSV hospitalization rates reported in 2 studies were 2.4 and 3.0 per 1000 person-years. In 5 studies that ascertained RSV-associated deaths among 4708 pregnant individuals, no deaths were reported. Three studies comparing RSV-positive and RSV-negative pregnant individuals found no difference in the odds of miscarriage, stillbirth, low birth weight, and small size for gestational age. RSV-positive pregnant individuals had higher odds of preterm delivery (odds ratio, 3.6 [95% CI, 1.3-10.3]).

CONCLUSIONS

Data on RSV-associated hospitalization rates are limited, but available estimates are lower than those reported in older adults and young children. As countries debate whether to include RSV vaccines in maternal vaccination programs, which are primarily intended to protect infants, this information could be useful in shaping vaccine policy decisions.

Knowledge, attitudes and behaviours of a sample of Italian paediatricians towards RSV and its preventive strategies: a cross-sectional study

BACKGROUND

Respiratory Syncytial Virus (RSV) infection mainly affects newborns, infants and young children aged < 2 years. Since an RSV vaccine is in the European Medicines Agency's waitlist validation, nowadays the prevention only includes passive immunization with monoclonal antibodies (mAb). In the present study we aimed at investigating Italian paediatricians' knowledge, attitudes and behaviours towards RSV and its prevention.

METHODS

From February to May 2023, an anonymous online questionnaire, with answers based on the Likert scale, was administered to a sample of Italian paediatricians' members of the Italian Society of Paediatrics. Descriptive and inferential statistical analyses were performed using STATA 17.

RESULTS

The paediatricians who answered the questionnaire were 507, mostly women (70.6%), aged 30-45 (33.1%), employed in hospitals in 66.6% of cases. The 10.8% of respondents reported that RSV is transmitted only among children younger than 2 years of age and 80.33% of participants that school-age children are not at risk of developing severe forms of RSV disease. The 25% of participants thought that active immunization is currently available to prevent RSV infection and 35.7% that does not exist passive immunization to prevent RSV for infants and newborns aged < 2 years. The 97.5% of physicians managed bronchiolitis cases and 65.6% of participants did not prescribe the administration of mAb. Higher age, seniority and RSV knowledge score were found to be associated with having a higher mAb knowledge score (p < 0.001) and having a higher RSV knowledge was associated with a higher mAb knowledge score (p < 0.001). The logistic regression model found that the odds of a positive attitude towards mAB knowledge score increased by over 3 times (OR 3.23, 95% CI [1.41, 7.40], p = 0.006) for being female and the odds of a positive attitude towards mAB knowledge score increased by almost 10 times (OR 9.73, 95% CI [3.06, 30.89], p < 0.001) for a one-unit increase in RSV knowledge score.

CONCLUSIONS

Paediatricians' limited knowledge or awareness could represent a barrier to the implementation of preventive strategies against RSV infection. Strategies to improve paediatricians' education on RSV prevention are, therefore, crucial.

Reduction of acute respiratory infections in day-care by non-pharmaceutical interventions: a narrative review

Objective

Children who start in day-care have 2-4 times as many respiratory infections compared to children who are cared for at home, and day-care staff are among the employees with the highest absenteeism. The extensive new knowledge that has been generated in the COVID-19 era should be used in the prevention measures we prioritize. The purpose of this narrative review is to answer the questions: Which respiratory viruses are the most significant in day-care centers and similar indoor environments? What do we know about the transmission route of these viruses? What evidence is there for the effectiveness of different non-pharmaceutical prevention measures?

Design

Literature searches with different terms related to respiratory infections in humans, mitigation strategies, viral transmission mechanisms, and with special focus on day-care, kindergarten or child nurseries, were conducted in PubMed database and Web of Science. Searches with each of the main viruses in combination with transmission, infectivity, and infectious spread were conducted separately supplemented through the references of articles that were retrieved.

Results

Five viruses were found to be responsible for ≈95% of respiratory infections: rhinovirus, (RV), influenza virus (IV), respiratory syncytial virus (RSV), coronavirus (CoV), and adenovirus (AdV). Novel research, emerged during the COVID-19 pandemic, suggests that most respiratory viruses are primarily transmitted in an airborne manner carried by aerosols (microdroplets).

Conclusion

Since airborne transmission is dominant for the most common respiratory viruses, the most important preventive measures consist of better indoor air quality that reduces viral concentrations and viability by appropriate ventilation strategies. Furthermore, control of the relative humidity and temperature, which ensures optimal respiratory functionality and, together with low resident density (or mask use) and increased time outdoors, can reduce the occurrence of respiratory infections.

Safety and Immunogenicity of a Revaccination With a Respiratory Syncytial Virus Prefusion F Vaccine in Older Adults: A Phase 2b Study

BACKGROUND

In the previous (parent) study, 2 doses of different formulations of an investigational vaccine against respiratory syncytial virus (RSVPreF3 OA) were well tolerated and immunogenic in older adults. This multicenter phase 2b extension study assessed safety and immunogenicity of a revaccination (third) dose of the 120 μg RSVPreF3-AS01E formulation.

METHODS

In total, 122 older adults (60-80 years), previously vaccinated with 2 doses of RSVPreF3-AS01E formulations (containing 30, 60, or 120 μg RSVPreF3 antigen), received an additional 120 μg RSVPreF3-AS01E dose 18 months after dose 2. Vaccine safety was evaluated in all participants up to 6 months and immunogenicity in participants who received 120 μg RSVPreF3-AS01E doses until 1 month after dose 3.

RESULTS

Similar to the parent study, mostly mild-to-moderate solicited adverse events and no vaccine-related serious adverse events or potential immune-mediated disorders were reported. Neutralizing titers and cell-mediated immune responses persisted for 18 months after 2-dose vaccination. Dose 3 increased RSV-specific neutralizing titers against RSV-A and RSV-B and median CD4+ T-cell frequencies. After dose 3, RSV-specific neutralizing titers but not CD4+ T-cell frequencies were below levels detected 1 month after dose 1.

CONCLUSIONS

Revaccination with 120 μg RSVPreF3-AS01E 18 months after dose 2 is well tolerated and immunogenic in older adults.

CLINICAL TRIALS REGISTRATION

NCT04657198; EudraCT, 2020-000692-21.

Determining the timing of respiratory syncytial virus (RSV) epidemics: a systematic review, 2016 to 2021; method categorisation and identification of influencing factors

BackgroundThere is currently no standardised approach to estimate respiratory syncytial virus (RSV) epidemics' timing (or seasonality), a critical information for their effective prevention and control.AimWe aimed to provide an overview of methods to define RSV seasonality and identify factors supporting method choice or interpretation/comparison of seasonal estimates.MethodsWe systematically searched PubMed and Embase (2016-2021) for studies using quantitative approaches to determine the start and end of RSV epidemics. Studies' features (data-collection purpose, location, regional/(sub)national scope), methods, and assessment characteristics (case definitions, sampled population's age, in/outpatient status, setting, diagnostics) were extracted. Methods were categorised by their need of a denominator (i.e. numbers of specimens tested) and their retrospective vs real-time application. Factors worth considering when choosing methods and assessing seasonal estimates were sought by analysing studies.ResultsWe included 32 articles presenting 49 seasonality estimates (18 thereof through the 10% positivity threshold method). Methods were classified into eight categories, two requiring a denominator (1 retrospective; 1 real-time) and six not (3 retrospective; 3 real-time). A wide range of assessment characteristics was observed. Several studies showed that seasonality estimates varied when methods differed, or data with dissimilar assessment characteristics were employed. Five factors (comprising study purpose, application time, assessment characteristics, healthcare system and policies, and context) were identified that could support method choice and result interpretation.ConclusionMethods and assessment characteristics used to define RSV seasonality are heterogeneous. Our categorisation of methods and proposed framework of factors may assist in choosing RSV seasonality methods and interpretating results.

Clinical features and outcomes of influenza and RSV coinfections: a report from Canadian immunization research network serious outcomes surveillance network

BACKGROUND

Influenza and RSV coinfections are not commonly seen but are concerning as they can lead to serious illness and adverse clinical outcomes among vulnerable populations. Here we describe the clinical features and outcomes of influenza and RSV coinfections in hospitalized adults.

METHODS

A cohort study was performed with pooled active surveillance in hospitalized adults ≥ 50 years from the Serious Outcomes Surveillance Network of the Canadian Immunization Research Network (CIRN SOS) during the 2012/13, 2013/14, and 2014/15 influenza seasons. Descriptive statistics summarized the characteristics of influenza/RSV coinfections. Kaplan-Meier estimated the probability of survival over the first 30 days of hospitalization.

RESULTS

Over three influenza seasons, we identified 33 cases of RSV and influenza coinfection, accounting for 2.39 cases per 1,000 hospitalizations of patients with acute respiratory illnesses. Adults aged 50 + years commonly reported cough (81.8%), shortness of breath (66.7%), sputum production (45.5%), weakness (33.3%), fever (27.3%), and nasal congestion (24.2%) as constitutional and lower respiratory tract infection symptoms. The mortality rate was substantial (12.1%), and age, comorbidity burden, and frailty were associated with a higher risk for adverse clinical outcomes.

CONCLUSIONS

Older adults are at higher risk for complications from influenza and RSV coinfections, especially those over 65 with a high comorbidity burden and frailty.

Respiratory syncytial virus among hospitalized patients of severe acute respiratory infection in Bhutan: Cross-sectional study

Introduction

Respiratory syncytial virus (RSV) is a leading cause of lower respiratory tract infections worldwide, particularly in young children. In Bhutan, respiratory disease continues to be among the top 10 diseases of morbidity for several years. This study aimed to estimate the prevalence of RSV among hospitalized patients with severe acute respiratory infection (SARI) in Bhutan.

Method

Respiratory specimens were collected from SARI patients of all ages in 2016 and 2018 following influenza surveillance guidelines. Specimens were tested for influenza and RSV, human metapneumovirus, adenovirus, and human parainfluenza virus types 1, 2, and 3 using real-time reverse-transcription polymerase chain reaction assay. Descriptive statistics were used to analyze the result in STATA 16.1.

Result

Of the 1339 SARI specimens tested, 34.8% were positive for at least one viral pathogen. RSV was detected in 18.5% of SARI cases, followed by influenza in 13.4% and other respiratory viruses in 3%. The median age of SARI cases was 3 (IQR: 0.8-21 years) years. RSV detection was higher among children aged 0-6 (Adj OR: 3.03; 95% CI: 1.7-5.39) and 7-23 months (Adj OR: 3.01; 95% CI: 1.77-5.12) compared with the children aged 5-15 years. RSV was also associated with breathing difficulty (Adj OR: 1.73; 95% CI: 1.17-2.56) and pre-existing lung disease, including asthma (Adj OR: 2.78; 95% CI: 0.99-7.8).

Conclusion

Respiratory viruses were detected in a substantial proportion of SARI hospitalizations in Bhutan.

Vaccination for Respiratory Syncytial Virus: A Narrative Review and Primer for Clinicians

Respiratory syncytial virus (RSV) poses a significant burden on public health, causing lower respiratory tract infections in infants, young children, older adults, and immunocompromised individuals. Recent development and licensure of effective RSV vaccines provide a promising approach to lessening the associated morbidity and mortality of severe infections. This narrative review aims to empower clinicians with the necessary knowledge to make informed decisions regarding RSV vaccination, focusing on the prevention and control of RSV infections, especially among vulnerable populations. The paper explores the available RSV vaccines and existing evidence regarding their efficacy and safety in diverse populations. Synthesizing this information for clinicians can help the latter understand the benefits and considerations associated with RSV vaccination, contributing to improved patient care and public health outcomes.

Respiratory syncytial virus infection and novel interventions

The large global burden of respiratory syncytial virus (RSV) respiratory tract infections in young children and older adults has gained increased recognition in recent years. Recent discoveries regarding the neutralization-specific viral epitopes of the pre-fusion RSV glycoprotein have led to a shift from empirical to structure-based design of RSV therapeutics, and controlled human infection model studies have provided early-stage proof of concept for novel RSV monoclonal antibodies, vaccines and antiviral drugs. The world's first vaccines and first monoclonal antibody to prevent RSV among older adults and all infants, respectively, have recently been approved. Large-scale introduction of RSV prophylactics emphasizes the need for active surveillance to understand the global impact of these interventions over time and to timely identify viral mutants that are able to escape novel prophylactics. In this Review, we provide an overview of RSV interventions in clinical development, highlighting global disease burden, seasonality, pathogenesis, and host and viral factors related to RSV immunity.

Circulation of human respiratory syncytial virus and new ON1 genotype in northern Viet Nam, 2017-2020

Objective

Human respiratory syncytial virus (RSV) is a primary cause of paediatric severe acute respiratory infection (SARI) worldwide, especially in developing countries. We investigated the genetic characteristics of RSV in northern Viet Nam to determine the prevalence and distribution of subtypes as well as the diversity and transmission patterns of genotypes.

Methods

In two facilities, from January 2017 to December 2020, 1563 clinical specimens were collected from paediatric patients hospitalized with SARI and tested for RSV. Selected positive samples underwent sequencing analysis targeting the second hypervariable region of the G gene using next-generation sequencing.

Results

The RSV positivity rate was 28.02% (438/1563 samples), and prevalence was highest in children aged < 1 year (43.84%; 192/438). Subtype RSV-A accounted for 53.42% (234/438) of cases, RSV-B for 45.89% (201/438), and there was coinfection in 0.68% (3/438). Both subtypes cocirculated and peaked during August-September in each year of the study. Phylogenetic analysis showed that RSV-A samples belonged to the ON1 genotype, which has three subgenotypes: ON1.1, ON1.2 and ON1.3. However, we did not find the 72-nucleotide duplication in the second hypervariable region of the G gene, a characteristic of genotype ON1, in any RSV-A samples. RSV-B samples belonged to genotype BA9.

Discussion

Our results provide additional molecular characterization of RSV infections in Viet Nam. Specially, our study is the first to report the absence of the 72-nucleotide duplication in the G gene of RSV-A genotype ON1 in Viet Nam, which may help in understanding the genetic evolution of RSV and be useful for vaccine development in the future.

Optimal site of care for administration of extended half-life respiratory syncytial virus (RSV) antibodies to infants in the United States (US)

INTRODUCTION

New extended half-life antibodies for the single-dose prevention of medically attended (MA) respiratory syncytial virus (RSV) lower respiratory tract infection (LRTI) have been developed for administration to all infants before or during their first RSV season. For infants born during the season, administration as soon as feasible after birth would provide optimal protection and minimize access disparities. The objective of this study was to assess the time from birth hospitalization discharge to the first outpatient visit (FOV) among US infants in order to determine optimal site of administration for the extended half-life antibody.

MATERIAL AND METHODS

This retrospective, observational, time-to-event analysis uses the Merative™ MarketScan® Commercial and Multi-State Medicaid Databases. Time to FOV is reported separately for the COVID-19 and recent pre-COVID-19 eras and for commercially insured and Medicaid infants.

RESULTS

Overall, 73.8 % of Medicaid infants had an FOV within 5 days as compared to 84.7 % of commercially insured infants. Estimates were higher during the COVID-19 era. Urban commercially insured infants had much higher FOV completion than their counterparts. Among Medicaid infants, urban Black and rural White infants were least likely to complete their FOV within 5 days of birth hospitalization discharge.

DISCUSSION AND CONCLUSION

FOV within 5 days after birth hospitalization discharge for Medicaid infants is substantially lower than that of commercially insured infants. Approximately 1 in 4 Medicaid infants and 1 in 8 infants with commercial insurance did not have an outpatient visit within 5 days of birth hospitalization discharge. For US infants born during the RSV season, administration of extended half-life RSV antibodies in the newborn nursery prior to discharge would ensure optimal uptake and minimize access disparities.

Nirsevimab binding-site conservation in respiratory syncytial virus fusion glycoprotein worldwide between 1956 and 2021: an analysis of observational study sequencing data

BACKGROUND

Nirsevimab is an extended half-life monoclonal antibody to the respiratory syncytial virus (RSV) fusion protein that has been developed to protect infants for an entire RSV season. Previous studies have shown that the nirsevimab binding site is highly conserved. However, investigations of the geotemporal evolution of potential escape variants in recent (ie, 2015-2021) RSV seasons have been minimal. Here, we examine prospective RSV surveillance data to assess the geotemporal prevalence of RSV A and B, and functionally characterise the effect of the nirsevimab binding-site substitutions identified between 2015 and 2021.

METHODS

We assessed the geotemporal prevalence of RSV A and B and nirsevimab binding-site conservation between 2015 and 2021 from three prospective RSV molecular surveillance studies (the US-based OUTSMART-RSV, the global INFORM-RSV, and a pilot study in South Africa). Nirsevimab binding-site substitutions were assessed in an RSV microneutralisation susceptibility assay. We contextualised our findings by assessing fusion-protein sequence diversity from 1956 to 2021 relative to other respiratory-virus envelope glycoproteins using RSV fusion protein sequences published in NCBI GenBank.

FINDINGS

We identified 5675 RSV A and RSV B fusion protein sequences (2875 RSV A and 2800 RSV B) from the three surveillance studies (2015-2021). Nearly all (25 [100%] of 25 positions of RSV A fusion proteins and 22 [88%] of 25 positions of RSV B fusion proteins) amino acids within the nirsevimab binding site remained highly conserved between 2015 and 2021. A highly prevalent (ie, >40·0% of all sequences) nirsevimab binding-site Ile206Met:Gln209Arg RSV B polymorphism arose between 2016 and 2021. Nirsevimab neutralised a diverse set of recombinant RSV viruses, including new variants containing binding-site substitutions. RSV B variants with reduced susceptibility to nirsevimab neutralisation were detected at low frequencies (ie, prevalence <1·0%) between 2015 and 2021. We used 3626 RSV fusion-protein sequences published in NCBI GenBank between 1956 and 2021 (2024 RSV and 1602 RSV B) to show that the RSV fusion protein had lower genetic diversity than influenza haemagglutinin and SARS-CoV-2 spike proteins.

INTERPRETATION

The nirsevimab binding site was highly conserved between 1956 and 2021. Nirsevimab escape variants were rare and have not increased over time.

FUNDING

AstraZeneca and Sanofi.

Clinical and economic hospital burden of acute respiratory infection (BARI) due to respiratory syncytial virus in Spanish children, 2015-2018

Respiratory syncytial virus (RSV) is a leading cause of acute lower respiratory infection (ALRI) in children, causing frequent outpatient visits and hospitalizations. Our study aimed to describe the clinical and direct economic burden of ALRI hospitalizations related to RSV in children in Spain and the characteristics of patients and their episodes. In this retrospective study, ALRI hospitalizations in children aged < 5 years for 2015-2018 were reviewed using anonymized administrative public hospital discharge data from Spain. Three case definitions were considered: (a) RSV-specific; (b) RSV-specific and unspecified acute bronchiolitis (RSV-specific and bronchiolitis); and (c) RSV-specific and unspecified ALRI (RSV-specific and ALRI). The study reported a mean of 36,743 yearly admissions potentially due to RSV, resulting in a mean annual cost of €87.1 million. RSV-specific codes accounted for 39.2% of cases, unspecified acute bronchiolitis for 20.1%, and other unspecified ALRI codes for the remaining 40.6%. The mean hospitalization rate per 1,000 children was 55.5 in the first year of life, 16.0 in the second, and 5.4 between 24 and 59 months. A considerable proportion of cases occurred in children under two years old (> 80.4%) and even during the first year of life (> 61.7%). Otherwise healthy children accounted for 92.9% of hospitalizations and 83.3% of costs during the period. Children born preterm accounted for 1.3% of hospitalizations and 5.7% of costs. The findings revealed that RSV still contributes to a high burden on the Spanish health care system. Children under one year of age and otherwise healthy term infants accounted for most of the substantial clinical and economic burden of RSV. Current evidence potentially underestimates the true epidemiology and burden of severe RSV infection; thus, further studies focusing on the outpatient setting are needed.

Resurgence of Respiratory Syncytial Virus in Children: An Out-of-Season Epidemic in Portugal

INTRODUCTION

An out-of-season increase in respiratory syncytial virus (RSV) incidence was observed in Portugal from June 2021 onwards, revealing a continuing surge in cases throughout 2021/2022 autumn/winter. We aimed to describe this out-of-season epidemic and define its epidemic period, by analysing RSV incidence from week 40 of 2020 (2020-W40) to week 18 of 2022 (2022-W18).

MATERIAL AND METHODS

Surveillance data on weekly RSV laboratory confirmed cases, in Portugal, was used to monitor RSV incidence using CUSUM test methodology for count data.

RESULTS

In 2021-W23, the CUSUM score identified a significant increase in the risk of RSV. By that time, the percentage of RSV positive tests rose from 1% in 2021-W22 (3/265) to 6% in 2021-W23 (18/298). Despite a sharp decrease in RSV incidence on 2021-W33 and on 2022-W02, the CUSUM score stayed over the limit up to 2022-W07, indicating that the RSV activity remained at an epidemic level. Distinct peaks of RSV cases were observed between 2021-W30 and 2021-W32 (average of 77 RSV cases per week) and between 2021-W39 and 2021-W41 (average of 79 RSV cases per week) with positivity rates around 60%.

CONCLUSION

An out-of-season RSV epidemic was identified, with a longer epidemic period compared with previous seasons. Possible reasons include relaxation of COVID-19 physical distancing measures and a greater proportion of population susceptible to disease. As several factors may change the pattern of RSV activity, countries should implement year-round surveillance RSV surveillance systems. These findings might have an impact on public health planning regarding future RSV surges, namely, on the palivizumab prophylaxis period for high-risk infants.

Estimating the cost-effectiveness of maternal vaccination and monoclonal antibodies for respiratory syncytial virus in Kenya and South Africa

BACKGROUND

Respiratory syncytial virus (RSV) causes a substantial burden of acute lower respiratory infection in children under 5 years, particularly in low- and middle-income countries (LMICs). Maternal vaccine (MV) and next-generation monoclonal antibody (mAb) candidates have been shown to reduce RSV disease in infants in phase 3 clinical trials. The cost-effectiveness of these biologics has been estimated using disease burden data from global meta-analyses, but these are sensitive to the detailed age breakdown of paediatric RSV disease, for which there have previously been limited data.

METHODS

We use original hospital-based incidence data from South Africa (ZAF) and Kenya (KEN) collected between 2010 and 2018 of RSV-associated acute respiratory infection (ARI), influenza-like illness (ILI), and severe acute respiratory infection (SARI) as well as deaths with monthly age-stratification, supplemented with data on healthcare-seeking behaviour and costs to the healthcare system and households. We estimated the incremental cost per DALY averted (incremental cost-effectiveness ratio or ICER) of public health interventions by MV or mAb for a plausible range of prices (5-50 USD for MV, 10-125 USD for mAb), using an adjusted version of a previously published health economic model of RSV immunisation.

RESULTS

Our data show higher disease incidence for infants younger than 6 months of age in the case of Kenya and South Africa than suggested by earlier projections from community incidence-based meta-analyses of LMIC data. Since MV and mAb provide protection for these youngest age groups, this leads to a substantially larger reduction of disease burden and, therefore, more favourable cost-effectiveness of both interventions in both countries. Using the latest efficacy data and inferred coverage levels based on antenatal care (ANC-3) coverage (KEN: 61.7%, ZAF: 75.2%), our median estimate of the reduction in RSV-associated deaths in children under 5 years in Kenya is 10.5% (95% CI: 7.9, 13.3) for MV and 13.5% (10.7, 16.4) for mAb, while in South Africa, it is 27.4% (21.6, 32.3) and 37.9% (32.3, 43.0), respectively. Starting from a dose price of 5 USD, in Kenya, net cost (for the healthcare system) per (undiscounted) DALY averted for MV is 179 (126, 267) USD, rising to 1512 (1166, 2070) USD at 30 USD per dose; for mAb, it is 684 (543, 895) USD at 20 USD per dose and 1496 (1203, 1934) USD at 40 USD per dose. In South Africa, a MV at 5 USD per dose would be net cost-saving for the healthcare system and net cost per DALY averted is still below the ZAF's GDP per capita at 40 USD dose price (median: 2350, 95% CI: 1720, 3346). For mAb in ZAF, net cost per DALY averted is 247 (46, 510) USD at 20 USD per dose, rising to 2028 (1565, 2638) USD at 50 USD per dose and to 6481 (5364, 7959) USD at 125 USD per dose.

CONCLUSIONS

Incorporation of new data indicating the disease burden is highly concentrated in the first 6 months of life in two African settings suggests that interventions against RSV disease may be more cost-effective than previously estimated.

The Importance of RSV Epidemiological Surveillance: A Multicenter Observational Study of RSV Infection during the COVID-19 Pandemic

The restrictive measures adopted worldwide against SARS-CoV-2 produced a drastic reduction in respiratory pathogens, including RSV, but a dramatic rebound was thereafter reported. In this multicenter retrospective observational study in 15 Pediatric Emergency Departments, all children <3 years old with RSV infection admitted between 1 September and 31 December 2021 were included and compared to those admitted in the same period of 2020 and 2019. The primary aim was to evaluate RSV epidemiology during and after the COVID-19 pandemic peak. The secondary aims were to evaluate the clinical features of children with RSV infection. Overall, 1015 children were enrolled: 100 in 2019, 3 in 2020 and 912 in 2021. In 2019, the peak was recorded in December, and in 2021, it was recorded in November. Comparing 2019 to 2021, in 2021 the median age was significantly higher and the age group 2-3 years was more affected. Admissions were significantly higher in 2021 than in 2020 and 2019, and the per-year hospitalization rate was lower in 2021 (84% vs. 93% in 2019), while the duration of admissions was similar. No difference was found in severity between 2019-2020-2021. In conclusion, after the COVID-19 pandemic, an increase in RSV cases in 2021 exceeding the median seasonal peak was detected, with the involvement of older children, while no difference was found in severity.

Burden of Respiratory Syncytial Virus Related Acute Lower Respiratory Tract Infection in Hospitalized Thai Children: A 6-Year National Data Analysis

Objectives: This study sought to determine the epidemiology, seasonal variations, morbidity, and mortality of respiratory syncytial virus (RSV) infection among hospitalized children with lower respiratory tract infection in Thailand. In addition, we assessed the risk factors associated with severe RSV lower respiratory tract infection (LRTI)-related morbidity and mortality. Methods: The data were reviewed retrospectively from the National Health Security Office for hospitalized children younger than 18 years old diagnosed with RSV-related LRTI in Thailand, between the fiscal years of 2015 to 2020. The RSV-related LRTIs were identified using the International Statistical Classification of Diseases and Related Health Problems, 10th Revision, Thai Modification. ICD-10-TM codes J12.1, J20.5, and J21.0, which represent respiratory syncytial virus pneumonia, acute bronchitis due to respiratory syncytial virus, and acute bronchiolitis due to respiratory syncytial virus, respectively, were studied. Results: During the study period, RSV-related LRTI accounted for 19,340 of the 1,610,160 hospital admissions due to LRTI. RSV pneumonia was the leading cause of hospitalization (13,684/19,340; 70.76%), followed by bronchiolitis (2849/19,340; 14.73%) and bronchitis (2807/19,340; 14.51%), respectively. The highest peak incidence of 73.55 percent occurred during Thailand’s rainy season, from August to October. The mortality rate of RSV-related LRTI in infants younger than 1 year of age was 1.75 per 100,000 person years, which was significantly higher than that of children 1 to younger than 5 years old and children 5 to younger than 18 years old (0.21 per 100,000 person years and 0.01 per 100,000 person years, respectively, p-value < 0.001). Factors associated with mortality were congenital heart disease, hematologic malignancy, malnutrition, and neurological disease. Conclusions: In children with RSV LRTI, pneumonia was the leading cause of hospitalization. The admission rate was highest during the rainy season. Mortality from RSV-related LRTI was higher in children under 1 year old and in children with underlying illnesses; future preventive interventions should target these groups of patients.

Neighborhood environmental factors linked to hospitalizations of older people for viral lower respiratory tract infections in Spain: a case-crossover study

BACKGROUND

Lower respiratory tract viral infection (LRTI) is a significant cause of morbidity-mortality in older people worldwide. We analyzed the association between short-term exposure to environmental factors (climatic factors and outdoor air pollution) and hospital admissions with a viral LRTI diagnosis in older adults.

METHODS

We conducted a bidirectional case-crossover study in 6367 patients over 65 years of age with viral LRTI and residential zip code in the Spanish Minimum Basic Data Set. Spain's State Meteorological Agency was the source of environmental data. Associations were assessed using conditional logistic regression. P-values were corrected for false discovery rate (q-values).

RESULTS

Almost all were hospital emergency admissions (98.13%), 18.64% were admitted to the intensive care unit (ICU), and 7.44% died. The most frequent clinical discharge diagnosis was influenza (90.25%). LRTI hospital admissions were more frequent when there were lower values of temperature and O₃ and higher values of relative humidity and NO₂. The regression analysis adjusted by temperatures and relative humidity showed higher concentrations at the hospital admission for NO₂ [compared to the lag time of 1-week (q-value< 0.001) and 2-weeks (q-value< 0.001)] and O₃ [compared to the lag time of 3-days (q-value< 0.001), 1-week (q-value< 0.001), and 2-weeks (q-value< 0.001)] were related to a higher odds of hospital admissions due to viral LRTI. Moreover, higher concentrations of PM₁₀ at the lag time of 1-week (q-value = 0.023) and 2-weeks (q-value = 0.002), and CO at the lag time of 3-days (q-value = 0.023), 1-week (q-value< 0.001) and 2-weeks (q-value< 0.001)], compared to the day of hospitalization, were related to a higher chances of hospital admissions with viral LRTI.

CONCLUSION

Unfavorable environmental factors (low temperatures, high relative humidity, and high concentrations of NO₂, O₃, PM₁₀, and CO) increased the odds of hospital admissions with viral LRTI among older people, indicating they are potentially vulnerable to these environmental factors.

Environmental factors linked to hospital admissions in young children due to acute viral lower respiratory infections: A bidirectional case-crossover study

OBJECTIVE

This study evaluated the association of the short-term exposure to environmental factors (relative humidity, temperature, NO₂, SO₂, O₃, PM₁₀, and CO) with hospital admissions due to acute viral lower respiratory infections (ALRI) in children under two years before the COVID-19 era.

METHODS

We performed a bidirectional case-crossover study in 30,445 children with ALRI under two years of age in the Spanish Minimum Basic Data Set (MBDS) from 2013 to 2015. Environmental data were obtained from Spain's State Meteorological Agency (AEMET). The association was assessed by conditional logistic regression.

RESULTS

Lower temperature one week before the day of the event (hospital admission) (q-value = 0.012) and higher relative humidity one week (q-value = 0.003) and two weeks (q-value<0.001) before the day of the event were related to a higher odds of hospital admissions. Higher NO₂ levels two weeks before the event were associated with hospital admissions (q-value<0.001). Moreover, higher concentrations on the day of the event for SO₂ (compared to lag time of 1-week (q-value = 0.026) and 2-weeks (q-value<0.001)), O₃ (compared to lag time of 3-days (q-value<0.001), 1-week (q-value<0.001), and 2-weeks (q-value<0.001)), and PM₁₀ (compared to lag time of 2-weeks (q-value<0.001)) were related to an increased odds of hospital admissions for viral ALRI.

CONCLUSION

Short-term exposure to environmental factors (climatic conditions and ambient air contaminants) was linked to a higher likelihood of hospital admissions due to ALRI. Our findings emphasize the importance of monitoring environmental factors to assess the odds of ALRI hospital admissions and plan public health resources.

Assessing the Clinical and Socioeconomic Burden of Respiratory Syncytial Virus in Children Aged Under 5 Years in Primary Care: Protocol for a Prospective Cohort Study in England and Report on the Adaptations of the Study to the COVID-19 Pandemic

Background

Respiratory syncytial virus (RSV) commonly causes lower respiratory tract infections and hospitalization in children. In 2019-2020, the Europe-wide RSV ComNet standardized study protocol was developed to measure the clinical and socioeconomic disease burden of RSV infections among children aged <5 years in primary care. RSV has a recognized seasonality in England.

Objective

We aimed to describe (1) the adaptations of the RSV ComNet standardized study protocol for England and (2) the challenges of conducting the study during the COVID-19 pandemic.

Methods

This study was conducted by the Oxford-Royal College of General Practitioners Research and Surveillance Centre—the English national primary care sentinel network. We invited all (N=248) general practices within the network that undertook virology sampling to participate in the study by recruiting eligible patients (registered population: n=3,056,583). Children aged <5 years with the following case definition of RSV infection were included in the study: those consulting a health care practitioner in primary care with symptoms meeting the World Health Organization’s definition of acute respiratory illness or influenza-like illness who have laboratory-confirmed RSV infection. The parents/guardians of these cases were asked to complete 2 previously validated questionnaires (14 and 30 days postsampling). A sample size of at least 100 RSV-positive cases is required to estimate the percentage of children that consult in primary care who need hospitalization. Assuming a swab positivity rate of 20% in children aged <5 years, we estimated that 500 swabs are required. We adapted our method for the pandemic by extending sampling planned for winter 2020-2021 to a rolling data collection, allowing verbal consent and introducing home swabbing because of increased web-based consultations during the COVID-19 pandemic.

Results

The preliminary results of the data collection between International Organization for Standardization (ISO) weeks 1-41 in 2021 are described. There was no RSV detected in the winter of 2020-2021 through the study. The first positive RSV swab collected through the sentinel network in England was collected in ISO week 17 and then every week since ISO week 25. In total, 16 (N=248, 6.5%) of the virology-sampling practices volunteered to participate; these were high-sampling practices collecting the majority of eligible swabs across the sentinel network—200 (43.8%) out of 457 swabs, of which 54 (N=200, 27%) were positive for RSV.

Conclusions

Measures to control the COVID-19 pandemic meant there was no circulating RSV last winter; however, RSV has circulated out of season, as detected by the sentinel network. The sentinel network practices have collected 40% (200/500) of the required samples, and 27% (54/200) were RSV positive. We have demonstrated the feasibility of implementing a European-standardized RSV disease burden study protocol in England during a pandemic, and we now need to recruit to this adapted protocol.

International Registered Report Identifier (IRRID)

DERR1-10.2196/38026

Resurgence of Respiratory Syncytial Virus Infection During COVID-19 Pandemic Among Children in Shanghai, China

Respiratory syncytial virus (RSV) is the most common pathogen causing acute lower respiratory tract infection (LRTI) in children. RSV usually peaks in winter and declines by early spring in China. The outbreak of coronavirus disease 2019 (COVID-19) was reported to bring changes to the transmission pattern of respiratory pathogens including RSV. Here in this paper, we analyzed RSV-positive nasopharyngeal aspirates from inpatients in the Children’s Hospital of Fudan University from October 2019 to October 2021 and compared the clinical features of the RSV-positive patients before and during COVID-19. We found an atypical upsurge of RSV infection in the late summer of 2021 after a major suppression in 2020. RSV B was the main subtype spreading among children throughout the study. Phylogenetic analysis revealed that all RSV A strains belonged to ON1 genotype and all RSV B strains were BA9 genotype. Deduced amino acid analysis displayed different substitutions in the RSV strains observed before and during COVID-19. Demographic analysis suggested that males and infants aged under 5 months were the main populations infected with RSV by gender and age, respectively. Less severe clinical outcomes were observed in patients during COVID-19 than before the pandemic, especially in RSV B-positive patients. Our findings described the epidemiological changes in RSV infection brought by COVID-19, which further underscored the importance of continuous surveillance of RSV in the shadow of COVID-19 at both local and global scales.

International changes in respiratory syncytial virus (RSV) epidemiology during the COVID-19 pandemic: Association with school closures

BACKGROUND

Little RSV activity was observed during the first expected RSV season since the COVID-19 pandemic. Multiple countries later experienced out-of-season RSV resurgences, yet their association with non-pharmaceutical interventions (NPIs) is unclear. This study aimed to describe the changes in RSV epidemiology during the COVID-19 pandemic and to estimate the association between individual NPIs and the RSV resurgences.

METHODS

RSV activity from Week (W)12-2020 to W44-2021 was compared with three pre-pandemic seasons using RSV surveillance data from Brazil, Canada, Chile, France, Israel, Japan, South Africa, South Korea, Taiwan, the Netherlands and the United States. Changes in nine NPIs within 10 weeks before RSV resurgences were described. Associations between NPIs and RSV activity were assessed with linear mixed models. Adherence to NPIs was not taken into account.

RESULTS

Average delay of the first RSV season during the COVID-19 pandemic was 39 weeks (range: 13-88 weeks). Although the delay was <40 weeks in six countries, a missed RSV season was observed in Brazil, Chile, Japan, Canada and South Korea. School closures, workplace closures, and stay-at-home requirements were most commonly downgraded before an RSV resurgence. Reopening schools and lifting stay-at-home requirements were associated with increases of 1.31% (p = 0.04) and 2.27% (p = 0.06) in the deviation from expected RSV activity.

CONCLUSION

The first RSV season during the COVID-19 pandemic was delayed in the 11 countries included. Reopening of schools was consistently associated with increased RSV activity. As NPIs were often changed concomitantly, the association between RSV activity and school closures may be partly attributed to other NPIs.

Incidence of respiratory syncytial virus lower respiratory tract infections during the first 2 years of life: A prospective study across diverse global settings

Background

The true burden of lower respiratory tract infections (LRTIs) due to respiratory syncytial virus (RSV) remains unclear. This study aimed to provide more robust, multinational data on RSV-LRTI incidence and burden in the first 2 years of life.

Methods

This prospective, observational cohort study was conducted in Argentina, Bangladesh, Canada, Finland, Honduras, South Africa, Thailand, and United States. Children were followed for 24 months from birth. Suspected LRTIs were detected via active (through regular contacts) and passive surveillance. RSV and other viruses were detected from nasopharyngeal swabs using PCR-based methods.

Results

Of 2401 children, 206 (8.6%) had 227 episodes of RSV-LRTI. Incidence rates (IRs) of first episode of RSV-LRTI were 7.35 (95% confidence interval [CI], 5.88–9.08), 5.50 (95% CI, 4.21–7.07), and 2.87 (95% CI, 2.18–3.70) cases/100 person-years in children aged 0–5, 6–11, and 12–23 months. IRs for RSV-LRTI, severe RSV-LRTI, and RSV hospitalization tended to be higher among 0–5 month olds and in lower-income settings. RSV was detected for 40% of LRTIs in 0–2 month olds and for approximately 20% of LRTIs in older children. Other viruses were codetected in 29.2% of RSV-positive nasopharyngeal swabs.

Conclusions

A substantial burden of RSV-LRTI was observed across diverse settings, impacting the youngest infants the most.

Clinical Trials Registration. NCT01995175.

HRSV prefusion-F protein with Adju-Phos adjuvant induces long-lasting Th2-biased immunity in mice

The development of human respiratory syncytial virus (hRSV) vaccine has been hampered by the risk of enhanced respiratory disease (ERD) which was induced by highly skewed toward Th2 immune response. In our previous study, we expressed the recombinant pre-F protein using Escherichia coli BL21, called RBF. To verify if the RBF protein could cause ERD, we tested the immunogenicity and safety of RBF with a commercial alum adjuvant (GMP-grade Adju-Phos). RBF alone and RBF/Adju-Phos elicited long-lasting protective antibodies and a cellular immune response in mice after three immunizations. Unfortunately, compared with the mice in RBF group, mice in RBF/Adju-Phos generated a serious Th2 humoral immune response that elicited Th2-mediated lung pathology. From the IL-4+:IFNγ+ ratio, there was also a robust Th2 cellullar immunologic response in the RBF/Adju-Phos group. This study demonstrates that it may not be enough for RBF to increase the titer of neutralizing antibodies. A balanced immune response must be induced for hRSV vaccine safety.