Characteristics of the delayed respiratory syncytial virus epidemic, 2020/2021, Rhône Loire, France

The severity of respiratory syncytial virus infection in children during the SARS-CoV-2/COVID-19 pandemic: A nationwide study of 11,915 cases in Germany

PURPOSE

Respiratory syncytial virus (RSV) infection is a major cause of childhood hospitalization. The COVID-19 pandemic has disrupted the usual seasonal pattern of RSV, resulting in high activity during the off-season. This study aims to evaluate the effects of the pandemic on the severity of RSV infections.

METHODS

Data from 11,915 children hospitalized due to RSV infection between 2016 and 2022 were analyzed. The hospitalized patients were categorized into two groups, from January 2016 to February 2020 (PreCoV19 group) and from March 2020 to December 2022 (CoV19 group). The hospitalization duration, intensive care unit (ICU) admissions, length of stay at ICU, mechanical ventilation requirement and duration, Elixhauser comorbidity index scores, and in-hospital mortality were analyzed.

RESULTS

Children in the PreCoV19 group had a mean age of 0.4 ± 0.7, whereas those in the CoV19 group had a mean age of 0.6 ± 1.0 years. Children during the pandemic had significantly shorter hospital stays (4.3 ± 2.6 days) compared to children of the pre-pandemic period (4.9 ± 3.3 days). Although ICU admission rates did not change, the duration of ICU stays decreased in the CoV19 group. Moreover, the in-hospital mortality did not differ between the groups. A multivariable analysis showed that younger age, regardless of the pandemic period, was associated with prolonged hospital stays, higher ICU admission rates, and an increased requirement for mechanical ventilation.

CONCLUSION

Our findings highlight significant changes of the clinical characteristics of RSV infections during the pandemic, with implications for clinical management and public health strategies.

Inpatient burden of respiratory syncytial virus (RSV) in Switzerland, 2003 to 2021: an analysis of administrative data

BackgroundRespiratory syncytial virus (RSV) is a leading cause of acute respiratory infections and hospitalisations in infants (age < 1 year) and young children. Little is known on RSV epidemiology and related inpatient healthcare resource use (HCRU) in Switzerland.AimTo explore RSV-related hospitalisations, inpatient HCRU and medical costs in all age groups, and risk factors for infant hospitalisations in Switzerland.MethodsWe used national hospital registry data from 2003 to 2021 identifying RSV cases with ICD-10-GM codes, and described demographic characteristics, HCRU and associated medical costs of RSV inpatients. The effect of risk factors on infant hospitalisation was estimated with logistic regression.ResultsWe observed a general increase and biannual pattern in RSV hospitalisations between 2003/04 and 2018/19, with 3,575 hospitalisations in 2018/19 and 2,487 in 2019/20 before numbers declined in 2020/21 (n = 902). Around two thirds of all hospitalisations occurred in infants. Mean (median) age was 118 (85) days in hospitalised infants and 74 (77) years in hospitalised adult patients (> 18 years); 7.2% of cases required intensive care unit stay. Mean inpatient medical costs were estimated at EUR 8,046. Most (90.8%) hospitalised infants with RSV were born after 35 weeks of gestation without bronchopulmonary dysplasia or congenital heart disease. Low birth weight, gestational age and congenital disorders were associated with a higher risk for hospitalisation.ConclusionsRSV leads to a substantial number of hospitalisations and peaks in hospital capacity utilisation. Measures to protect all infants from an RSV hospitalisation are essential in addressing this public health challenge.

Sequence analysis of respiratory syncytial virus cases reveals a novel subgroup -B strain circulating in north-central Italy after pandemic restrictions

BACKGROUND

Following the pandemic restrictions, the epidemiology of respiratory syncytial virus (RSV) has changed, leading to intense hospitalization peaks.

OBJECTIVES

This study, conducted at multiple sites in Italy, aimed to describe the temporal dynamics of two post-COVID-19 RSV epidemics. Additionally, the circulating RSV-A and -B lineages were characterized and compared to those found in 2018 and 2019.

STUDY DESIGN

Respiratory specimens and data were collected from RSV-positive patients, both inpatients, and outpatients, of all ages at three sites in north-central Italy. To analyze these samples, roughly one-sixth were sequenced in the attachment glycoprotein G gene and subjected to phylogenetic and mutational analyses, including pre-pandemic sequences from north-central Italy.

RESULTS

The first post-pandemic surge of RSV cases was quite intense, occurring from October 2021 to early January 2022. The subsequent RSV epidemic (from November 2022 to early March 2023) also had a high impact, characterized by a rise in elderly patient cases. Post-pandemic cases of RSV-A were caused by various strains present in Italy prior to COVID-19. In contrast, a distinct RSV-B lineage, which was concurrently spreading in other countries, was identified as the main cause of the surge in 2022-2023 but remained undetected in Italy before the pandemic.

CONCLUSIONS

This study describes the temporal dynamics of post-pandemic RSV subgroups and uncovers a lineage of RSV-B with high genetic divergence that may have increased the impact of decreased population immunity.

Global patterns of rebound to normal RSV dynamics following COVID-19 suppression

BACKGROUND

Annual epidemics of respiratory syncytial virus (RSV) had consistent timing and intensity between seasons prior to the SARS-CoV-2 pandemic (COVID-19). However, starting in April 2020, RSV seasonal activity declined due to COVID-19 non-pharmaceutical interventions (NPIs) before re-emerging after relaxation of NPIs. We described the unusual patterns of RSV epidemics that occurred in multiple subsequent waves following COVID-19 in different countries and explored factors associated with these patterns.

METHODS

Weekly cases of RSV from twenty-eight countries were obtained from the World Health Organisation and combined with data on country-level characteristics and the stringency of the COVID-19 response. Dynamic time warping and regression were used to cluster time series patterns and describe epidemic characteristics before and after COVID-19 pandemic, and identify related factors.

RESULTS

While the first wave of RSV epidemics following pandemic suppression exhibited unusual patterns, the second and third waves more closely resembled typical RSV patterns in many countries. Post-pandemic RSV patterns differed in their intensity and/or timing, with several broad patterns across the countries. The onset and peak timings of the first and second waves of RSV epidemics following COVID-19 suppression were earlier in the Southern than Northern Hemisphere. The second wave of RSV epidemics was also earlier with higher population density, and delayed if the intensity of the first wave was higher. More stringent NPIs were associated with lower RSV growth rate and intensity and a shorter gap between the first and second waves.

CONCLUSION

Patterns of RSV activity have largely returned to normal following successive waves in the post-pandemic era. Onset and peak timings of future epidemics following disruption of normal RSV dynamics need close monitoring to inform the delivery of preventive and control measures.

Impact of COVID-19 Pandemic Restrictions on Respiratory Virus Patterns: Insights from RSV Surveillance in Gwangju, South Korea

The social restriction measures implemented due to the COVID-19 pandemic have impacted the pattern of occurrences of respiratory viruses. According to surveillance results in the Gwangju region of South Korea, respiratory syncytial virus (RSV) did not occur during the 2020/2021 season. However, there was a delayed resurgence in the 2021/2022 season, peaking until January 2022. To analyze this, a total of 474 RSV positive samples were investigated before and after the COVID-19 pandemic. Among them, 73 samples were selected for whole-genome sequencing. The incidence rate of RSV in the 2021/2022 season after COVID-19 was found to be approximately three-fold higher compared to before the pandemic, with a significant increase observed in the age group from under 2 years old to under 5 years old. Phylogenetic analysis revealed that, for RSV-A, whereas four lineages were observed before COVID-19, only the A.D.3.1 lineage was observed during the 2021/2022 season post-pandemic. Additionally, during the 2022/2023 season, the A.D.1, A.D.3, and A.D.3.1 lineages co-circulated. For RSV-B, while the B.D.4.1.1 lineage existed before COVID-19, both the B.D.4.1.1 and B.D.E.1 lineages circulated after the pandemic. Although atypical RSV occurrences were not due to new lineages, there was an increase in the frequency of mutations in the F protein of RSV after COVID-19. These findings highlight the need to continue monitoring changes in RSV occurrence patterns in the aftermath of the COVID-19 pandemic to develop and manage strategies in response.

Respiratory Syncytial Virus and Influenza Infections in Children in Ulaanbaatar, Mongolia, 2015-2021

BACKGROUND

Data available for RSV and influenza infections among children < 2 years in Mongolia are limited. We present data from four districts of Ulaanbaatar from April 2015 to June 2021.

METHODS

This study was nested in an enhanced surveillance project evaluating pneumococcal conjugate vaccine (PCV13) impact on the incidence of hospitalized lower respiratory tract infections (LRTIs). Our study was restricted to children aged < 2 years with arterial O2 saturation < 93% and children with radiological pneumonia. Nasopharyngeal (NP) swabs collected at admission were tested for RSV and influenza using qRT-PCR. NP swabs of all patients with radiological pneumonia and of a subset of randomly selected NP swabs were tested for S. pneumoniae (S.p.) by qPCR and for serotypes by culture and DNA microarray.

RESULTS

Among 5705 patients, 2113 (37.0%) and 386 (6.8%) had RSV and influenza infections, respectively. Children aged 2-6 months had a higher percentage of very severe RSV infection compared to those older than 6 months (42.2% versus 31.4%, p-value Fisher's exact = 0.001). S.p. carriage was detected in 1073/2281 (47.0%) patients. Among S.p. carriage cases, 363/1073 (33.8%) had S.p. and RSV codetection, and 82/1073 (7.6%) had S.p. and influenza codetection. S.p. codetection with RSV/influenza was not associated with more severe LRTIs, compared to only RSV/influenza cases.

CONCLUSION

In Mongolia, RSV is an important pathogen causing more severe LRTI in children under 6 months of age. Codetection of RSV or influenza virus and S.p. was not associated with increased severity.

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.

Changes in the global hospitalisation burden of respiratory syncytial virus in young children during the COVID-19 pandemic: a systematic analysis

BACKGROUND

The COVID-19 pandemic is reported to have affected the epidemiology of respiratory syncytial virus (RSV), which could have important implications for RSV prevention and control strategies. We aimed to assess the hospitalisation burden of RSV-associated acute lower respiratory infection (ALRI) in children younger than 5 years during the pandemic period and the possible changes in RSV epidemiology from a global perspective.

METHODS

We conducted a systematic literature search for studies published between Jan 1, 2020, and June 30, 2022, in MEDLINE, Embase, Global Health, Web of Science, the WHO COVID-19 Research Database, CINAHL, LILACS, OpenGrey, CNKI, WanFang, and CqVip. We included unpublished data on RSV epidemiology shared by international collaborators. Eligible studies reported data on at least one of the following measures for children (aged <5 years) hospitalised with RSV-associated ALRI: hospital admission rates, in-hospital case fatality ratio, and the proportion of hospitalised children requiring supplemental oxygen or requiring mechanical ventilation or admission to intensive care. We used a generalised linear mixed-effects model for data synthesis to measure the changes in the incidence, age distribution, and disease severity of children hospitalised with RSV-associated ALRI during the pandemic, compared with the year 2019.

FINDINGS

We included 61 studies from 19 countries, of which 14 (23%) studies were from the published literature (4052 identified records) and 47 (77%) were from unpublished datasets. Most (51 [84%]) studies were from high-income countries; nine (15%) were from upper-middle-income countries, one (2%) was from a lower-middle-income country (Kenya), and none were from a low-income country. 15 studies contributed to the estimates of hospitalisation rate and 57 studies contributed to the severity analyses. Compared with 2019, the rates of RSV-associated ALRI hospitalisation in all children (aged 0-60 months) in 2020 decreased by 79·7% (325 000 cases vs 66 000 cases) in high-income countries, 13·8% (581 000 cases vs 501 000 cases) in upper-middle-income countries, and 42·3% (1 378 000 cases vs 795 000 cases) in Kenya. In high-income countries, annualised rates started to rise in 2021, and by March, 2022, had returned to a level similar to 2019 (6·0 cases per 1000 children [95% uncertainty interval 5·4-6·8] in April, 2021, to March, 2022, vs 5·0 cases per 1000 children [3·6-6·8] in 2019). By contrast, in middle-income countries, rates remained lower in the latest period with data available than in 2019 (for upper-middle-income countries, 2·1 cases [0·7-6·1] in April, 2021, to March, 2022, vs 3·4 [1·2-9·7] in 2019; for Kenya, 2·2 cases [1·8-2·7] in 2021 vs 4·1 [3·5-4·7] in 2019). Across all time periods and income regions, hospitalisation rates peaked in younger infants (aged 0 to <3 months) and decreased with increasing age. A significantly higher proportion of children aged 12-24 months were hospitalised with RSV-associated ALRI in high-income and upper-middle-income countries during the pandemic years than in 2019, with odds ratios ranging from 1·30 (95% uncertainty interval 1·07-1·59) to 2·05 (1·66-2·54). No consistent changes in disease severity were observed.

INTERPRETATION

The hospitalisation burden of RSV-associated ALRI in children younger than 5 years was significantly reduced during the first year of the COVID-19 pandemic. The rebound in hospitalisation rates to pre-pandemic rates observed in the high-income region but not in the middle-income region by March, 2022, suggests a persistent negative impact of the pandemic on health-care systems and health-care access in the middle-income region. RSV surveillance needs to be established (or re-established) to monitor changes in RSV epidemiology, particularly in low-income and lower-middle-income countries.

FUNDING

EU Innovative Medicines Initiative Preparing for RSV Immunisation and Surveillance in Europe (PROMISE), Bill & Melinda Gates Foundation, and WHO.

Atypical age distribution and high disease severity in children with RSV infections during two irregular epidemic seasons throughout the COVID-19 pandemic, Germany, 2021 to 2023

BackgroundNon-pharmaceutical interventions (NPIs) during the COVID-19 pandemic affected respiratory syncytial virus (RSV) circulation worldwide.AimTo describe, for children aged < 5 years, the 2021 and 2022/23 RSV seasons in Germany.MethodsThrough data and 16,754 specimens from outpatient sentinel surveillance, we investigated RSV seasonality, circulating lineages, and affected children's age distributions in 2021 and 2022/23. Available information about disease severity from hospital surveillance was analysed for patients with RSV-specific diagnosis codes (n = 13,104). Differences between RSV seasons were assessed by chi-squared test and age distributions trends by Mann-Kendall test.ResultsRSV seasonality was irregular in 2021 (weeks 35-50) and 2022/23 (weeks 41-3) compared to pre-COVID-19 2011/12-2019/20 seasons (median weeks 51-12). RSV positivity rates (RSV-PR) were higher in 2021 (40% (522/1,291); p < 0.001) and 2022/23 (30% (299/990); p = 0.005) than in prior seasons (26% (1,430/5,511)). Known globally circulating RSV-A (lineages GA2.3.5 and GA2.3.6b) and RSV-B (lineage GB5.0.5a) strains, respectively, dominated in 2021 and 2022/23. In 2021, RSV-PRs were similar in 1 - < 2, 2 - < 3, 3 - < 4, and 4 - < 5-year-olds. RSV hospitalisation incidence in 2021 (1,114/100,000, p < 0.001) and in 2022/23 (1,034/100,000, p < 0.001) was approximately double that of previous seasons' average (2014/15-2019/20: 584/100,000). In 2022/23, proportions of RSV patients admitted to intensive care units rose (8.5% (206/2,413)) relative to pre-COVID-19 seasons (6.8% (551/8,114); p = 0.004), as did those needing ventilator support (6.1% (146/2,413) vs 3.8% (310/8,114); p < 0.001).ConclusionsHigh RSV-infection risk in 2-4-year-olds in 2021 and increased disease severity in 2022/23 possibly result from lower baseline population immunity, after NPIs diminished exposure to RSV.

Children Hospitalized With Respiratory Syncytial Virus Infection: A Pre Versus Late COVID-19 Pandemic Comparison

Our study aimed to compare children under 5 years hospitalized with respiratory syncytial virus in prepandemic and late-pandemic periods. We included 209 children at the Dijon University Hospital (France). We observed a nearly 3-fold increase in the number of cases in the late period, with older children, but less frequently requiring intensive care. These observations could help prepare a new pandemic.

Drug repurposing screen identifies lonafarnib as respiratory syncytial virus fusion protein inhibitor

Respiratory syncytial virus (RSV) is a common cause of acute lower respiratory tract infection in infants, older adults and the immunocompromised. Effective directly acting antivirals are not yet available for clinical use. To address this, we screen the ReFRAME drug-repurposing library consisting of 12,000 small molecules against RSV. We identify 21 primary candidates including RSV F and N protein inhibitors, five HSP90 and four IMPDH inhibitors. We select lonafarnib, a licensed farnesyltransferase inhibitor, and phase III candidate for hepatitis delta virus (HDV) therapy, for further follow-up. Dose-response analyses and plaque assays confirm the antiviral activity (IC50: 10-118 nM). Passaging of RSV with lonafarnib selects for phenotypic resistance and fixation of mutations in the RSV fusion protein (T335I and T400A). Lentiviral pseudotypes programmed with variant RSV fusion proteins confirm that lonafarnib inhibits RSV cell entry and that these mutations confer lonafarnib resistance. Surface plasmon resonance reveals RSV fusion protein binding of lonafarnib and co-crystallography identifies the lonafarnib binding site within RSV F. Oral administration of lonafarnib dose-dependently reduces RSV virus load in a murine infection model using female mice. Collectively, this work provides an overview of RSV drug repurposing candidates and establishes lonafarnib as a bona fide fusion protein inhibitor.

Epidemiological characteristics of respiratory viruses in children during the COVID-19 epidemic in Chengdu, China

IMPORTANCE

During the coronavirus disease 2019 epidemic, the Chinese government launched and used a series of nonpharmaceutical interventions (NPIs), including banning social gatherings, wearing face masks, home isolation, and maintaining hand hygiene, to control the disease spread. Whether and how NPIs influence other respiratory viruses in children remain unclear. In this article, we analyzed relative data and found that the number of samples and positive proportion of respiratory viruses decreased significantly compared with that before the epidemic. Clinicians and public health policymakers should pay attention to changes in the epidemic trends and types of respiratory viruses and maintain monitoring of respiratory-related viruses to avoid possible abnormal rebounds and epidemic outbreaks of these viruses.

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.

Characteristics of respiratory viruses' circulation through a six-year period (2016-2022) in a pediatric population in Normandy, France, and the impact of COVID-19 pandemic

IMPORTANCE

The report highlights an epidemiological change in the circulation of respiratory viruses in pediatric populations due to strategies adopted against COVID-19 pandemic. COVID-19 has resulted in a significant increase in requests for multiplex respiratory research to identify the virus responsible for the symptoms. The diagnostic needs have increased, and the number of samples analyzed in 2021-2022 is equal to the samples analyzed over the four epidemic periods preceding the pandemic. The report suggests the importance of active surveillance of respiratory viruses' circulation and new recommendations for respiratory virus detection in pediatric patients.

Modeling the impact of COVID-19 nonpharmaceutical interventions on respiratory syncytial virus transmission in South Africa

Background

The South African government employed various nonpharmaceutical interventions (NPIs) to reduce the spread of SARS-CoV-2. Surveillance data from South Africa indicates reduced circulation of respiratory syncytial virus (RSV) throughout the 2020-2021 seasons. Here, we use a mechanistic transmission model to project the rebound of RSV in the two subsequent seasons.

Methods

We fit an age-structured epidemiological model to hospitalization data from national RSV surveillance in South Africa, allowing for time-varying reduction in RSV transmission during periods of COVID-19 circulation. We apply the model to project the rebound of RSV in the 2022 and 2023 seasons.

Results

We projected an early and intense outbreak of RSV in April 2022, with an age shift to older infants (6-23 months old) experiencing a larger portion of severe disease burden than typical. In March 2022, government alerts were issued to prepare the hospital system for this potentially intense outbreak. We then assess the 2022 predictions and project the 2023 season. Model predictions for 2023 indicate that RSV activity has not fully returned to normal, with a projected early and moderately intense wave. We estimate that NPIs reduced RSV transmission between 15% and 50% during periods of COVID-19 circulation.

Conclusions

A wide range of NPIs impacted the dynamics of the RSV outbreaks throughout 2020-2023 in regard to timing, magnitude, and age structure, with important implications in a low- and middle-income countries (LMICs) setting where RSV interventions remain limited. More efforts should focus on adapting RSV models to LMIC data to project the impact of upcoming medical interventions for this disease.

Respiratory syncytial virus in children: epidemiology and clinical impact post-COVID-19

PURPOSE OF REVIEW

Respiratory syncytial virus (RSV) remains a leading cause of mortality and morbidity worldwide. RSV seasonality was disrupted by COVID-19-associated nonpharmaceutical interventions (NPIs). We review RSV seasonality, molecular epidemiology, clinical manifestations, and community awareness to inform future prevention strategies.

RECENT FINDINGS

An initial reduction of RSV disease observed with NPIs, and subsequent global resurgence was associated with a collapse in genetic diversity. A lack of immunity is suggested to have contributed to the resurgence of RSV cases experienced post COVID-19. The median age of children admitted with RSV increased during the resurgence, likely secondary to the expanded cohort of RSV-immune naive children. The pandemic also played a role in increased community awareness, which can be utilized as part of a coordinated public health effort to introduce prevention strategies. Further education on signs and symptoms of RSV is still required.

SUMMARY

mAbs and maternal vaccines targeting RSV have the potential to reduce paediatric morbidity, however this new era of RSV prevention will require ongoing research to facilitate community awareness and engagement, and better respiratory surveillance. Tackling the global burden of RSV will require a coordinated effort and measures to ensure access and affordability of new prevention strategies.

Re-Emergence of HMPV in Gwangju, South Korea, after the COVID-19 Pandemic

The non-pharmaceutical interventions implemented to prevent the spread of COVID-19 have affected the epidemiology of other respiratory viruses. In South Korea, Human metapneumovirus (HMPV) typically occurs from winter to the following spring; however, it was not detected for two years during the COVID-19 pandemic and re-emerged in the fall of 2022, which is a non-epidemic season. To examine the molecular genetic characteristics of HMPV before and after the COVID-19 pandemic, we analyzed 427 HMPV-positive samples collected in the Gwangju area from 2018 to 2022. Among these, 24 samples were subjected to whole-genome sequencing. Compared to the period before the COVID-19 pandemic, the incidence rate of HMPV in 2022 increased by 2.5-fold. Especially in the age group of 6-10 years, the incidence rate increased by more than 4.5-fold. In the phylogenetic analysis results, before the COVID-19 pandemic, the A2.2.2 lineage was predominant, while in 2022, the A2.2.1 and B2 lineage were observed. The non-pharmaceutical interventions implemented after COVID-19, such as social distancing, have reduced opportunities for exposure to HMPV, subsequently leading to decreased acquisition of immunity. As a result, HMPV occurred during non-epidemic seasons, influencing the age distribution of its occurrences.

Pediatric RSV-Associated Hospitalizations Before and During the COVID-19 Pandemic

Importance

Respiratory syncytial virus (RSV) is a leading cause of pediatric hospitalizations.

Objective

To describe the epidemiology and burden of RSV-associated hospitalizations among children and adolescents in Canadian tertiary pediatric hospitals from 2017 to 2022, including changes during the COVID-19 pandemic.

Design, Setting, and Participants

This cross-sectional study was conducted during 5 RSV seasons (2017-2018 to 2021-2022) at 13 pediatric tertiary care centers from the Canadian Immunization Monitoring Program Active (IMPACT) program. Hospitalized children and adolescents aged 0 to 16 years with laboratory-confirmed RSV infection were included.

Main Outcomes and Measures

The proportion of all-cause admissions associated with RSV and counts and proportions of RSV hospitalizations with intensive care unit (ICU) admission, prolonged stay (≥7 days), and in-hospital mortality were calculated overall and by season, age group, and region. Seasonality was described using epidemic curves. RSV hospitalizations for 2021-2022 were compared with those in the prepandemic period of 2017-2018 through 2019-2020. Bonferroni corrections were applied to P values to adjust for multiple statistical comparisons.

Results

Among 11 014 RSV-associated hospitalizations in children and adolescents (6035 hospitalizations among male patients [54.8%]; 5488 hospitalizations among patients aged <6 months [49.8%]), 2594 hospitalizations (23.6%) had admission to the ICU, of which 1576 hospitalizations (60.8%) were among children aged less than 6 months. The median (IQR) hospital stay was 4 (2-6) days. The mean (SD) number of RSV-associated hospitalizations during prepandemic seasons was 2522 (88.8) hospitalizations. There were 58 hospitalizations reported in 2020-2021, followed by 3170 hospitalizations in 2021-2022. The proportion of all-cause hospitalizations associated with RSV increased from a mean of 3.2% (95% CI, 3.1%-3.3%) before the pandemic to 4.5% (95% CI, 4.3%-4.6%) in 2021-2022 (difference, 1.3 percentage points; 95% CI, 1.1-1.5 percentage points; corrected P < .001). A significant increase in RSV-associated hospitalizations was found in 2021-2022 for 3 provinces (difference range, 2.5 percentage points; 95% CI, 1.4-3.6 percentage points for Quebec to 2.9 percentage points; 95% CI, 1.4-3.5 percentage points for Alberta; all corrected P < .001). Age, sex, ICU admission, prolonged length of stay, and case fatality rate did not change in 2021-2022 compared with the prepandemic period. Interregional differences in RSV seasonality were accentuated in 2021-2022, with peaks for 1 province in October, 4 provinces in December, and 3 provinces in April, or May.

Conclusions and Relevance

This study found that the burden of RSV-associated hospitalizations in Canadian pediatric hospitals was substantial, particularly among infants aged less than 6 months, and RSV hospitalizations increased in 2021-2022 compared with the prepandemic period, while severity of illness remained similar. These findings suggest that RSV preventive strategies for infants aged less than 6 months would be associated with decreased RSV disease burden in children.

Respiratory Syncytial Virus Infections in Polish Pediatric Patients from an Expert Perspective

Respiratory syncytial virus (RSV) is the most common pathogen causing respiratory tract infections in infants, affecting over 90% of children within the first two years of life. It may cause lower respiratory tract infections, which constitute a significant healthcare burden both in the primary and secondary care settings. Meanwhile, the data regarding RSV disease in Poland is scarce, and published data significantly differs from the numbers reported for other countries with longstanding surveillance and reporting systems. A literature review and an expert panel were conducted to (1) understand the healthcare burden of RSV infections in Poland; (2) collect data on infection seasonality, patient pathway, and management patterns; and (3) evaluate RSV infection surveillance in Poland. According to the literature, RSV is the major agent responsible for non-influenza respiratory diseases in Poland. The reported rates of hospitalization for RSV infections are 267.5/100,000 for children under 5 years of age and 1132.1/100,000 for those under 1 year of age. Comparisons with data from other countries suggest that these values may be underestimated, possibly due to insufficient access to microbiological testing and a low awareness of RSV. Infections occur mainly between December and April, however, this pattern has changed following the implementation of preventive measures for coronavirus disease 2019 in the past few years. According to available reports, bronchodilators, antibiotics, corticosteroids, and X-ray imaging have been frequently used. The surveillance system in Poland has limitations, but these may be overcome due to recent changes in healthcare law as well as the availability and reimbursement of diagnostic tests.

Nonlinear and Multidelayed Effects of Meteorological Drivers on Human Respiratory Syncytial Virus Infection in Japan

In this study, we aimed to characterize the nonlinear and multidelayed effects of multiple meteorological drivers on human respiratory syncytial virus (HRSV) infection epidemics in Japan. The prefecture-specific weekly time-series of the number of newly confirmed HRSV infection cases and multiple meteorological variables were collected for 47 Japanese prefectures from 1 January 2014 to 31 December 2019. We combined standard time-series generalized linear models with distributed lag nonlinear models to determine the exposure-lag-response association between the incidence relative risks (IRRs) of HRSV infection and its meteorological drivers. Pooling the 2-week cumulative estimates showed that overall high ambient temperatures (22.7 °C at the 75th percentile compared to 16.3 °C) and high relative humidity (76.4% at the 75th percentile compared to 70.4%) were associated with higher HRSV infection incidence (IRR for ambient temperature 1.068, 95% confidence interval [CI], 1.056-1.079; IRR for relative humidity 1.045, 95% CI, 1.032-1.059). Precipitation revealed a positive association trend, and for wind speed, clear evidence of a negative association was found. Our findings provide a basic picture of the seasonality of HRSV transmission and its nonlinear association with multiple meteorological drivers in the pre-HRSV-vaccination and pre-coronavirus disease 2019 (COVID-19) era in Japan.

Epidemiological Changes in Respiratory Viral Infections in Children: The Influence of the COVID-19 Pandemic

BACKGROUND

Viruses are the major cause of acute respiratory infections in children, causing important morbimortality. Before the COVID-19 pandemic, in temperate regions, respiratory viruses displayed a typical seasonality in transmission. A disruption in this pattern was observed in several countries during the pandemic, with low prevalence during the typical season, and an interseasonal rise. We evaluated the effects of the COVID-19 pandemic in the epidemiology of non-COVID viral respiratory infections in children, in a tertiary care hospital in Portugal.

METHODS

Between March 2020 and August 2022, nasopharyngeal samples from children with respiratory symptoms in the Emergency Department (ED) and the Pediatric Ward were tested for RSV, influenza and other respiratory viruses, by real-time reverse transcriptase PCR (RT-PCR).

RESULTS

A seasonal variation was observed from 2018 to 2020, with prevalence increasing in winter (mainly RSV and influenza). In the winter of 2020/21, when measures to mitigate SARS-CoV-2 transmission were stricter, there was a disruption of the seasonal pattern, with unusually low numbers. In the summer of 2021, when measures were being relaxed, there was an atypical rise. In June 2021, RSV was first detected and peaked in October. Influenza (Influenza A H3) was detected for the first time in February 2022, peaking in March/April.

CONCLUSIONS

These findings show a disruption of the seasonality of viral respiratory infections in children during the pandemic, with a virtual elimination during the months of usually higher prevalence, and a subsequent out-of-season increase, coinciding with variations in the measures implemented to control the SARS-CoV-2 transmission, and confirming their efficacy.

Molecular Diversity of Human Respiratory Syncytial Virus before and during the COVID-19 Pandemic in Two Neighboring Japanese Cities

Human respiratory syncytial viruses (HRSVs) are divided into subgroups A and B, which are further divided based on the nucleotide sequence of the second hypervariable region (HVR) of the attachment glycoprotein (G) gene. Understanding the molecular diversity of HRSV before and during the coronavirus disease 2019 (COVID-19) pandemic can provide insights into the effects of the pandemic on HRSV dissemination and guide vaccine development. Here, we analyzed HRSVs isolated in Fukushima Prefecture from September 2017 to December 2021. Specimens from pediatric patients were collected at two medical institutions in neighboring cities. A phylogenetic tree based on the second HVR nucleotide sequences was constructed using the Bayesian Markov chain Monte Carlo method. HRSV-A (ON1 genotype) and HRSV-B (BA9 genotype) were detected in 183 and 108 specimens, respectively. There were differences in the number of HRSV strains within clusters prevalent at the same time between the two hospitals. The genetic characteristics of HRSVs in 2021 after the COVID-19 outbreak were similar to those in 2019. HRSVs within a cluster may circulate within a region for several years, causing an epidemic cycle. Our findings add to the existing knowledge of the molecular epidemiology of HRSV in Japan. IMPORTANCE Understanding the molecular diversity of human respiratory syncytial viruses during pandemics caused by different viruses can provide insights that can guide public health decisions and vaccine development.

Temporal Shift of the Respiratory Syncytial Virus Epidemic Peak for the Years 2020-2023 in Marseille, Southern France

Respiratory syncytial virus is among the most common causes of respiratory infections. Typically, this viral infection has a seasonality during the cold months but with the SARS-CoV-2 pandemic this has been considerably modified. Here, we studied the epidemiology of this virus in university hospitals of Marseille, South of France, over the period 2020 to 2023. We tested in our laboratory from July 2020 to October 2021 16,516 nasopharyngeal swabs from 16,468 patients for RSV infection using different qPCR assays. We then analyzed data from previous and subsequent winters (from 2018 to 2023) and previous summers (from 2015 to 2021). A total of 676 patients were RSV-positive; their mean age was 3 years and 91 were under 5 years of age. We observed a delay of 4 months of the RSV epidemic's onset compared to other years with an epidemic that peaked in March 2021. We had significantly more RSV-positive cases during summer 2021 compared to previous summers, whereas the incidence of RSV infections was not significantly higher during winter 2022 versus previous winters. Moreover, 494 patients were diagnosed as RSV-positive in the emergency unit and 181 were subsequently hospitalized, and 34 patients were diagnosed RSV-positive while already in the intensive care unit. Over all the study periods, 38 patients diagnosed as RSV-positive died, the majority of whom (23/28) were over 65 years of age. These data show an atypical evolution of the incidence of RSV infections in our city and is another example of the unpredictability of infectious disease epidemiology.

Impact of the COVID-19 pandemic on the prevalence of influenza A and respiratory syncytial viruses elucidated by wastewater-based epidemiology

Since the COVID-19 pandemic, a decrease in the prevalence of Influenza A virus (IAV) and respiratory syncytial virus (RSV) has been suggested by clinical surveillance. However, there may be potential biases in obtaining an accurate overview of infectious diseases in a community. To elucidate the impact of the COVID-19 on the prevalence of IAV and RSV, we quantified IAV and RSV RNA in wastewater collected from three wastewater treatment plants (WWTPs) in Sapporo, Japan, between October 2018 and January 2023, using highly sensitive EPISENS™ method. From October 2018 to April 2020, the IAV M gene concentrations were positively correlated with the confirmed cases in the corresponding area (Spearman's r = 0.61). Subtype-specific HA genes of IAV were also detected, and their concentrations showed trends that were consistent with clinically reported cases. RSV A and B serotypes were also detected in wastewater, and their concentrations were positively correlated with the confirmed clinical cases (Spearman's r = 0.36-0.52). The detection ratios of IAV and RSV in wastewater decreased from 66.7 % (22/33) and 42.4 % (14/33) to 4.56 % (12/263) and 32.7 % (86/263), respectively in the city after the COVID-19 prevalence. The present study demonstrates the potential usefulness of wastewater-based epidemiology combined with the preservation of wastewater (wastewater banking) as a tool for better management of respiratory viral diseases.

Changing patterns of infectious diseases in children during the COVID-19 pandemic

Each infectious disease has had its own epidemic pattern and seasonality for decades. However, public health mitigation measures during the coronavirus disease 2019 (COVID-19) pandemic have resulted in changing epidemic patterns of infectious diseases. Stringent measures resulted in low incidences of various infectious diseases during the outbreak of COVID-19, including influenza, respiratory syncytial virus, pneumococcus, enterovirus, and parainfluenza. Owing to the prevalence of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infections and subsequent immunity development, decreasing virulence of SARS-CoV-2, and worldwide immunization against SARS-CoV-2 in children beyond 6 months of age, mitigation measures are lifted country by country. Consequently, the immunity debt to infectious respiratory viruses other than SARS-CoV-2 contributed to the "off-season," "see-saw," and "upsurge" patterns of various infectious diseases in children. Moreover, apart from the persistence of SARS-CoV-2, the coexistence of other circulating viruses or bacterial outbreaks may lead to twindemics or tripledemics during the following years. Therefore, it is necessary to maintain hand hygiene and immunization policies against various pathogens to alleviate the ongoing impact of infectious diseases on children.

Understanding the age spectrum of respiratory syncytial virus associated hospitalisation and mortality burden based on statistical modelling methods: a systematic analysis

BACKGROUND

Statistical modelling studies based on excess morbidity and mortality are important for understanding RSV disease burden for age groups that are less frequently tested for RSV. We aimed to understand the full age spectrum of RSV morbidity and mortality burden based on statistical modelling studies, as well as the value of modelling studies in RSV disease burden estimation.

METHODS

The databases Medline, Embase and Global Health were searched to identify studies published between January 1, 1995, and December 31, 2021, reporting RSV-associated excess hospitalisation or mortality rates of any case definitions using a modelling approach. All reported rates were summarised using median, IQR (Interquartile range) and range by age group, outcome and country income group; where applicable, a random-effects meta-analysis was conducted to combine the reported rates. We further estimated the proportion of RSV hospitalisations that could be captured in clinical databases.

RESULTS

A total of 32 studies were included, with 26 studies from high-income countries. RSV-associated hospitalisation and mortality rates both showed a U-shape age pattern. Lowest and highest RSV acute respiratory infection (ARI) hospitalisation rates were found in 5-17 years (median: 1.6/100,000 population, IQR: 1.3-18.5) and < 1 year (2235.7/100,000 population, 1779.1-3552.5), respectively. Lowest and highest RSV mortality rates were found in 18-49 years (0.1/100,000 population, 0.06-0.2) and ≥ 75 years (80.0/100,000 population, 70.0-90.0) for high-income countries, respectively, and in 18-49 years (0.3/100,000 population, 0.1-2.4) and < 1 year (143.4/100,000 population, 143.4-143.4) for upper-middle income countries. More than 70% of RSV hospitalisations in children < 5 years could be captured in clinical databases whereas less than 10% of RSV hospitalisations could be captured in adults, especially for adults ≥ 50 years. Using pneumonia and influenza (P&I) mortality could potentially capture half of all RSV mortality in older adults but only 10-30% of RSV mortality in children.

CONCLUSIONS

Our study provides insights into the age spectrum of RSV hospitalisation and mortality. RSV disease burden using laboratory records alone could be substantially severely underreported for age groups ≥ 5 years. Our findings confirm infants and older adults should be prioritised for RSV immunisation programmes.

TRIAL REGISTRATION

PROSPERO CRD42020173430.

Resurgence of influenza and respiratory syncytial virus in Egypt following two years of decline during the COVID-19 pandemic: outpatient clinic survey of infants and children, October 2022

INTRODUCTION

Two years after unprecedented low rates of circulation of most common respiratory viruses (SARS-CoV-2), the Egyptian ARI surveillance system detected an increase in acute respiratory infections (ARIs) with a reduced circulation of the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), especially among school children. A national survey was conducted to estimate the burden and identify the viral causes of ARIs among children < 16 years of age.

METHODS

A one-day survey was carried out in 98 governmental outpatient clinics distributed all over Egypt 26 governorates. The four largest referral hospitals in each governorate where most influenza-like illness (ILI) patients seek care were selected. Using the WHO case definition, the first five patients < 16 years of age with ILI symptoms visiting the selected outpatient clinics on the survey day were enrolled. Basic demographic and clinical data of patients were collected using a linelist. Patients were swabbed and tested for SARS-CoV-2, influenza, and Respiratory Syncytial virus (RSV) by RT-PCR at the Central Laboratory in Cairo.

RESULTS

Overall, 530 patients enrolled, their mean age was 5.8 ± 4.2, 57.1% were males, and 70.2% reside in rural or semi-rural areas. Of all patients, 134 (25.3%) had influenza, 111 (20.9%) RSV, and 14 (2.8%) coinfections. Influenza-positive children were older compared to RSV, (7.2 ± 4.1, 4.3 ± 4.1, p < 0.001), with more than half of them (53.0%) being school students. Dyspnea was reported in RSV more than in influenza (62.2% vs. 49.3%, p < 0.05). Among RSV patients, children < 2 years had a higher rate of dyspnea than others (86.7% vs. 53.1%, < 0.001).

CONCLUSIONS

A resurgence of influenza and RSV was detected in Egypt in the 2022-2023 winter season. Influenza caused a higher rate of infection than RSV, while RSV caused more severe symptoms than influenza. Monitoring a broader range of respiratory pathogens is recommended to estimate the ARI burden and risky groups for severe disease in Egypt.

Respiratory syncytial virus infection in the modern era

PURPOSE OF REVIEW

Respiratory syncytial virus (RSV) continues to be a major cause of severe lower respiratory tract infection in infants, young children, and older adults. In this review, changes in the epidemiology of RSV during the coronavirus disease 2019 (COVID-19) pandemic are highlighted together with the role which increased molecular surveillance efforts will have in future in assessing the efficacy of vaccines and therapeutics.

RECENT FINDINGS

The introduction of nonpharmaceutical intervention (NPIs) strategies during the COVID-19 pandemic between 2020 and 2022 resulted in worldwide disruption to the epidemiology of RSV infections, especially with respect to the timing and peak case rate of annual epidemics. Increased use of whole genome sequencing along with efforts to better standardize the nomenclature of RSV strains and discrimination of RSV genotypes will support increased monitoring of relevant antigenic sites in the viral glycoproteins. Several RSV vaccine candidates based on subunit, viral vectors, nucleic acid, or live attenuated virus strategies have shown efficacy in Phase 2 or 3 clinical trials with vaccines using RSVpreF protein currently the closest to approval and use in high-risk populations. Finally, the recent approval and future use of the extended half-life human monoclonal antibody Nirsevimab will also help to alleviate the morbidity and mortality burden caused by annual epidemics of RSV infections.

SUMMARY

The ongoing expansion and wider coordination of RSV molecular surveillance efforts via whole genome sequencing will be crucial for future monitoring of the efficacy of a new generation of vaccines and therapeutics.

Epidemiological characteristics of seasonal influenza under implementation of zero-COVID-19 strategy in China

OBJECTIVE

Respiratory viral diseases have posed a persistent threat to public health due to their high transmissibility. Influenza virus and SARS-Cov-2 are both respiratory viruses that have caused global pandemics. A zero-COVID-19 strategy is a public health policy imposed to stop community transmission of COVID-19 as soon as it is detected. In this study, we aim to examine the epidemiological characteristics of seasonal influenza in the past five years before and after the emergence of COVID-19 in China and observe the possible impact of the strategy on influenza.

METHODS

Data from two data sources were retrospectively analyzed. A comparison on influenza incidence rate between Hubei and Zhejiang provinces was conducted based on data from the Chinese Center for Disease Control and Prevention (CDC). Then a descriptive and comparative analysis on seasonal influenza based on data from Zhongnan Hospital of Wuhan University and Hangzhou Ninth People`s Hospital before and after the outbreak of SARS-CoV-2 was conducted.

RESULTS

From 2010-2017, both provinces experienced relatively low influenza activity until the 1st week of 2018, when they reached peak incidence rates of 78.16/100000PY, 34.05/100000PY respectively. Since then, influenza showed an obvious seasonality in Hubei and Zhejiang until the onset of COVID-19. During 2020 and 2021, there was a dramatic decline in influenza activity compared to 2018 and 2019. However, influenza activity seemed to rebound at the beginning of 2022 and surged in summer, with positive rates of 20.52% and 31.53% in Zhongnan Hospital of Wuhan University and Hangzhou Ninth People`s Hospital respectively as of the time writing this article.

CONCLUSIONS

Our results reinforce the hypothesis that zero-COVID-19 strategy may impact the epidemiological pattern of influenza. Under the complex pandemic situation, implementation of NPIs could be a beneficial strategy containing not only COVID-19 but also influenza.

Bronchiolitis before and after the SARS-CoV-2 pandemic: Twelve years of experience in a Spanish paediatric hospital

INTRODUCTION

Acute bronchiolitis is the main cause of hospitalization in children under 2 years of age, with a regular seasonality, mostly due to the respiratory syncytial virus.

OBJECTIVES

To describe the epidemiology of bronchiolitis hospitalizations in our center in the last 12 years, and analyze the changes in clinical characteristics, microbiology, and adverse outcomes during the SARS-CoV-2 pandemic.

METHODS

Observational study including patients admitted for bronchiolitis between April 2010 and December 2021 in a Spanish tertiary paediatric hospital. Relevant demographic, clinical, microbiological, and adverse outcome variables were collected in an anonymized database. The pandemic period (April 2020 to December 2021) was compared to 2010-2015 seasons using appropriate statistical tests.

RESULTS

There were 2138 bronchiolitis admissions, with a mean of 195.6 per year between 2010 and 2019 and a 2-4-month peak between November and March. In the expected season of 2020, there was a 94.4% reduction of bronchiolitis hospitalizations, with only 11 cases admitted in the first year of the pandemic. Bronchiolitis cases increased from the summer of 2021 during a 6-month long peak, reaching a total of 171 cases. Length of stay was significantly shorter during the pandemic, but no differences were found in clinical and microbiological characteristics or other adverse outcomes.

CONCLUSIONS

The SARS-CoV-2 pandemic has modified the seasonality of bronchiolitis hospitalizations, with a dramatic decrease in cases during the expected season of 2020-2021, and an extemporaneous summer-autumn peak in 2021 with longer duration but similar patient characteristics and risk factors.

Hospital admissions and need for mechanical ventilation in children with respiratory syncytial virus before and during the COVID-19 pandemic: a Danish nationwide cohort study

BACKGROUND

The incidence of respiratory syncytial virus (RSV) increased in several countries after the relaxation of COVID-19 restrictions. We aimed to investigate the age-related risk of RSV-associated hospital admissions and need for mechanical ventilation during the RSV resurgence in summer and autumn 2021 compared with the four RSV seasons preceding the COVID-19 pandemic. We also aimed to describe the clinical complications necessitating mechanical ventilation.

METHODS

This population-based cohort study included patients aged 0-17 years admitted to hospital with RSV in Denmark during the RSV resurgence in summer and autumn 2021, and the four pre-COVID-19 RSV seasons (2016-17, 2017-18, 2018-19, and 2019-20). We retrieved data on RSV-associated hospital admissions from the Danish National Patient Registry and demographic and clinical details of children who received mechanical ventilation through prospective real-time data collection in 2021-22 and retrospective data collection for the 2016-17 to 2019-20 RSV seasons from all eight paediatric and neonatal intensive care units in Denmark. Risk factors for severe RSV disease were as defined as age younger than 3 months or severe comorbidities. We calculated the risk of RSV-associated hospital admissions per 100 000 population in each RSV season from week 21 to week 20 of the following year. We also calculated the risk rate of receiving mechanical ventilation per 100 000 population and 1000 RSV-associated hospital admissions during each RSV season from week 21 to week 20 of the following year. We calculated risk ratios (RRs) for hospital admission and mechanical ventilation by dividing the risk rate of hospital admission and mechanical ventilation in 2021-22 by annual mean risk rates in the four pre-COVID-19 RSV epidemics (2016-17 to 2019-20). We compared RRs using Fisher's exact test. We compared complications leading to intubation between children with and without risk factors for severe RSV disease. The study is registered at ClinicalTrials.gov, NCT05186597.

FINDINGS

Among 310 423 Danish children aged younger than 5 years, the mean number of RSV-associated hospital admissions increased from 1477 (SD 226) in the 2016-17 to 2019-20 RSV seasons to 3000 in the 2021-22 RSV season (RR 2·0 [95% CI 1·9-2·1]). 54 children with RSV received mechanical ventilation in 2021-22 compared with 15-28 annually in the 2016-17 to 2019-20 RSV seasons (2·3 [1·6-3·3]). The highest increase in hospital admissions and need for mechanical ventilation occurred among children aged 24-59 months (4·1 [3·6-4·7] for hospital admission; 4·6 [1·7-12·6] for mechanical ventilation). Among children admitted to hospital, the risk of mechanical ventilation was similar in 2021-22 and the four pre-COVID-19 seasons (risk rate 14·3 per 1000 RSV-associated hospital admissions [95% CI 10·4-19·3] vs 12·9 [10·1-16·1]; RR 1·1 [95% CI 0·8-1·6]). Across all RSV seasons studied, among children younger than 3 months or those with severe comorbidities, respiratory failure due to bronchiolitis led to mechanical ventilation in 69 (79%) of 87 children. Of 46 children with no risk factors for severe RSV, 40 (87%) received mechanical ventilation due to additional complications, including neurological (n=16; 35%), cardiac (n=1; 2%), and pulmonary complications (n=23; 50%; eg, wheeze responsive to bronchodilator therapy, severe bacterial co-infections, and pneumothorax).

INTERPRETATION

In Denmark, RSV disease did not seem to be more severe for the individual child during the RSV resurgence in 2021 following relaxation of COVID-19 restrictions. However, hospital admissions were higher among older children, possibly due to a postponed first RSV infection or no recent reinfection. Older children without risk factors for severe RSV disease had atypical complications that led to intubation. If new RSV-preventive interventions for healthy infants delay first RSV infection, a higher number of older children might be admitted to hospital due to atypical clinical phenotypes, rather than classical bronchiolitis.

FUNDING

National Ministry of Higher Education and Science and the Innovation Fund Denmark.

The effects of the COVID-19 pandemic on community respiratory virus activity

The emergence of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) caused substantial global morbidity and deaths, leading governments to turn to non-pharmaceutical interventions to slow down the spread of infection and lessen the burden on health care systems. These policies have evolved over the course of the COVID-19 pandemic, including after the availability of COVID-19 vaccines, with regional and country-level differences in their ongoing use. The COVID-19 pandemic has been associated with changes in respiratory virus infections worldwide, which have differed between virus types. Reductions in respiratory virus infections, including by influenza virus and respiratory syncytial virus, were most notable at the onset of the COVID-19 pandemic and continued in varying degrees through subsequent waves of SARS-CoV-2 infections. The decreases in community infection burden have resulted in reduced hospitalizations and deaths associated with non-SARS-CoV-2 respiratory infections. Respiratory virus evolution relies on the maintaining of a diverse genetic pool, but evidence of genetic bottlenecking brought on by case reduction during the COVID-19 pandemic has resulted in reduced genetic diversity of some respiratory viruses, including influenza virus. By describing the differences in these changes between viral species across different geographies over the course of the COVID-19 pandemic, we may better understand the complex factors involved in community co-circulation of respiratory viruses.

Application of a forecasting model to mitigate the consequences of unexpected RSV surge: Experience from the post-COVID-19 2021/22 winter season in a major metropolitan centre, Lyon, France

Background

The emergence of COVID-19 triggered the massive implementation of non-pharmaceutical interventions (NPI) which impacted the circulation of respiratory syncytial virus (RSV) during the 2020/2021 season.

Methods

A time-series susceptible-infected-recovered (TSIR) model was used early September 2021 to forecast the implications of this disruption on the future 2021/2022 RSV epidemic in Lyon urban population.

Results

When compared to observed hospital-confirmed cases, the model successfully captured the early start, peak timing, and end of the 2021/2022 RSV epidemic. These simulations, added to other streams of surveillance data, shared and discussed among the local field experts were of great value to mitigate the consequences of this atypical RSV outbreak on our hospital paediatric department.

Conclusions

TSIR model, fitted to local hospital data covering large urban areas, can produce plausible post-COVID-19 RSV simulations. Collaborations between modellers and hospital management (who are both model users and data providers) should be encouraged in order to validate the use of dynamical models to timely allocate hospital resources to the future RSV epidemics.

Temporal dynamics of RSV shedding and genetic diversity in adults during the COVID-19 pandemic in a French hospital, early 2021

Human respiratory syncytial virus (RSV) is responsible of lower respiratory tract infections which may be severe in infants, elderly and immunocompromised adults. Europe and North-American countries have observed a massive reduction of RSV incidence during the 2020-2021 winter season. Using a systematic RSV detection coupled to SARS-CoV-2 for all adult patients admitted at the Foch hospital (Suresnes, France) between January and March 2021 (n = 11,324), only eight RSV infections in patients with prolonged RNA shedding were diagnosed. RSV whole-genome sequencing revealed that six and two patients were infected by RSV groups A and B, respectively. RSV carriage lasted from 7 to at least 30 days disregarding of RSV lineage. The most prolonged RSV shedding was observed in an asymptomatic patient. We detected novel patient-specific non-synonymous mutations in the G glycoprotein gene, including a double identical mutation in the repeated region for one patient. No additional mutation occurred in the RSV genome over the course of infection in the four patients tested for. In conclusion, our results suggest that the temporal shift in the RSV epidemic is not likely to be explained by the emergence of a high frequency, unreported variant. Moreover, prolonged RSV carriages in asymptomatic patients could play a role in virus spread.

Epidemiological characteristics of respiratory viruses in hospitalized children during the COVID-19 pandemic in southwestern China

Background

Multinational studies have reported that the implementation of nonpharmaceutical interventions (NPIs) to control severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) transmission coincided with the decline of other respiratory viruses, such as influenza viruses and respiratory syncytial virus.

Objective

To investigate the prevalence of common respiratory viruses during the coronavirus disease 2019 (COVID-19) pandemic.

Methods

Respiratory specimens of children with lower respiratory tract infections (LRTIs) hospitalized at the Children's Hospital of Chongqing Medical University from January 1, 2018 to December 31, 2021 were collected. Seven common pathogens, including respiratory syncytial virus (RSV), adenovirus (ADV), influenza virus A and B (Flu A, Flu B), and parainfluenza virus types 1-3 (PIV1-3), were detected by a multiplex direct immunofluorescence assay (DFA). Demographic data and laboratory test results were analyzed.

Results

1) A total of 31,113 children with LRTIs were enrolled, including 8141 in 2018, 8681 in 2019, 6252 in 2020, and 8059 in 2021.The overall detection rates decreased in 2020 and 2021 (P < 0.001). The detection rates of RSV, ADV, Flu A, PIV-1, and PIV-3 decreased when NPIs were active from February to August 2020, with Flu A decreasing most predominantly, from 2.7% to 0.3% (P < 0.05). The detection rates of RSV and PIV-1 resurged and even surpassed the historical level of 2018-2019, while Flu A continued decreasing when NPIs were lifted (P < 0.05). 2) Seasonal patterns of Flu A completely disappeared in 2020 and 2021. The Flu B epidemic was observed until October 2021 after a long period of low detection in 2020. RSV decreased sharply after January 2020 and stayed in a nearly dormant state during the next seven months. Nevertheless, the detection rates of RSV were abnormally higher than 10% in the summer of 2021. PIV-3 decreased significantly after the COVID-19 pandemic; however, it atypically surged from August to November 2020.

Conclusion

The NPIs implemented during the COVID-19 pandemic affected the prevalence and seasonal patterns of certain viruses such as RSV, PIV-3, and influenza viruses. We recommend continuous surveillance of the epidemiological and evolutionary dynamics of multiple respiratory pathogens, especially when NPIs are no longer necessary.

Preventing Respiratory Syncytial Virus in Children in France: A Narrative Review of the Importance of a Reinforced Partnership Between Parents, Healthcare Professionals, and Public Health Authorities

The highly contagious respiratory syncytial virus (RSV) is responsible for up to approximately 50,000 hospitalisations during each RSV season in children aged under 5 years in France, with the burden greatest in infants younger than 1 year who were born at term. There is a need for a strategy to universally protect young children from RSV infection, and thereby reduce the pressure that RSV places every year on RSV-infected children, their parents, and French healthcare systems. Potential strategies currently undergoing clinical investigation include passive immunisation via maternal vaccination or administration of long-acting monoclonal antibodies at or soon after birth, followed by vaccination later in infancy or childhood. An ongoing partnership and collaboration between parents, public health authorities, and frontline primary healthcare will need to be reinforced once these new RSV prevention strategies are available, to facilitate their use and ensure that all children receive adequate protection from the start of their first RSV season.

A delayed resurgence of respiratory syncytial virus (RSV) during the COVID-19 pandemic: An unpredictable outbreak in a small proportion of children in the Southwest of Iran, April 2022

The global outbreak of coronavirus disease 2019 (COVID-19), an emerging disease caused by severe acute respiratory syndrome virus-2 (SARS-CoV-2), and strict restrictions implemented to control the infection have impacted the circulation and transmission of common seasonal viruses worldwide and subsequently the rate of hospitalizations in children at young ages. Respiratory syncytial virus (RSV) surprisingly disappeared in 2020-2021 in many countries due to lockdown and precautions were taken because of the COVID-19 pandemic. Herein, we showed a notable change in the rate of hospitalization and reported an unpredictable outbreak of RSV in a small proportion of children admitted to a children's hospital in Dezful (a city in Southwest Iran) in the early spring of 2022. We performed a descriptive study of hospitalized young children (aged ≤ 5 years) with acute respiratory infections. Together with clinical information, 30 nasopharyngeal swabs were prospectively collected and 3 important respiratory viruses (RSV, influenza viruses, and SARS-CoV-2) were tested through the real-time polymerase chain reaction (real-time PCR) method. The age distribution of 30 hospital-admitted children was 1 month to 5 years old and males were the most included subjects 18/30 (60%) in this study. Although the viral genome of SARS-CoV-2 and influenza viruses was not detected, the presence of RSV was confirmed in 16/30 (53.33%) patients. Results showed that the majority of RSV-infected cases were males 10/16 (62.5%), within 12 months of life, and had changes in parameters of the complete blood count. Almost all patients with RSV infection had a cough as the most common clinical manifestation and had no history of past medical conditions as a risk factor. The presented study is the first investigation that documented an outbreak of RSV infection in young children reported since the onset of the COVID-19 outbreak in Iran. Our cases highlight the potential threats of important but neglected pathogens during the ongoing pandemic as described here for RSV, which would be challenging by easing the preimposed restrictions.

Respiratory Syncytial Virus Pediatric Hospitalization in the COVID-19 Era

Respiratory syncytial virus (RSV) globally affects the population, mainly young children, potentially causing hospitalization. During the COVID-19 pandemic, non-pharmacological measures interfered with the circulation of most respiratory viruses. Then, with the discontinuation of restrictive measures, a new scenario appeared. With this scoping review, we want to globally explore whether the RSV paediatric hospitalization rate was influenced by COVID-19. This scoping review was performed according to PRISMA guidelines on PubMed using the Mesh terms "Respiratory Syncytial Viruses"[Mesh] AND "COVID-19"[Mesh] OR "SARS-CoV-2"[Mesh]. Among them, we identified studies pertaining to children and adolescents up to 18 years old hospitalized for RSV, including 18 records in the revision. With the onset of the COVID-19 pandemic, a drastic reduction in RSV hospitalization among the pediatric population in 2020-2021 season has been observed in the Northern and Southern hemispheres. After the relaxing of restrictive measures, unexpected outbreaks happened, leading to increased hospitalization and occupation of pediatric intensive care units.

The Scope of Respiratory Syncytial Virus Infection in a Tertiary Hospital in the Eastern Province of Saudi Arabia and the Change in Seasonal Pattern during and after the COVID-19 Pandemic

Background and Objectives: Respiratory syncytial virus (RSV) is a major cause of morbidity and hospital admission due to respiratory tract infection among infants and young children. The current study aims to describe the prevalence and the seasonal pattern of RSV during the previous seven years. Materials and Methods: Clinical data and RSV antigen and PCR test results were collected from patients’ medical records at King Fahd Hospital of the University in the Eastern Province of Saudi Arabia between January 2015 and February 2022. Results: The overall percentage of RSV detection was 26.3% (336/1279) among the tested individuals. RSV infection was more common among children below five years and elderly above 60 years of age. Two-thirds of the cases required hospitalization. The average hospital stay due to RSV infection was 6.5 days (range 0−56 days). The rate of hospitalization was higher among infants and younger children and decreased with age (p-value < 0.001). RSV infection was more prevalent between August and February and decreased appreciably between March and July. The peak level of infection was during December and January. No RSV infections were reported during the COVID-19 pandemic and the following winter. The cases increased again in August 2021, with an unusual out-of-season peak. Conclusions: RSV infection is one of the important causes of morbidity and hospitalization among infants and young children in Saudi Arabia. The seasonal pattern of infection has changed after the COVID-19 pandemic, and the physicians should be aware that infection may happen currently at different times throughout the year.

Determinants of RSV epidemiology following suppression through pandemic contact restrictions

INTRODUCTION

COVID-19 related non-pharmaceutical interventions (NPIs) led to a suppression of RSV circulation in winter 2020/21 in the UK and an off-season resurgence in Summer 2021. We explore how the parameters of RSV epidemiology shape the size and dynamics of post-suppression resurgence and what we can learn about them from the resurgence patterns observed so far.

METHODS

We developed an age-structured dynamic transmission model of RSV and sampled the parameters governing RSV seasonality, infection susceptibility and post-infection immunity, retaining simulations fitting the UK's pre-pandemic epidemiology by a set of global criteria consistent with likelihood calculations. From Spring 2020 to Summer 2021 we assumed a reduced contact frequency, returning to pre-pandemic levels from Spring 2021. We simulated transmission forwards until 2023 and evaluated the impact of the sampled parameters on the projected trajectories of RSV hospitalisations and compared these to the observed resurgence.

RESULTS

Simulations replicated an out-of-season resurgence of RSV in 2021. If unmitigated, paediatric RSV hospitalisation incidence in the 2021/22 season was projected to increase by 30-60% compared to pre-pandemic levels. The increase was larger if infection risk was primarily determined by immunity acquired from previous exposure rather than age-dependent factors, exceeding 90 % and 130 % in 1-2 and 2-5 year old children, respectively. Analysing the simulations replicating the observed early outbreak in 2021 in addition to pre-pandemic RSV data, we found they were characterised by weaker seasonal forcing, stronger age-dependence of infection susceptibility and higher baseline transmissibility.

CONCLUSION

COVID-19 mitigation measures in the UK stopped RSV circulation in the 2020/21 season and generated immunity debt leading to an early off-season RSV epidemic in 2021. A stronger dependence of infection susceptibility on immunity from previous exposure increases the size of the resurgent season. The early onset of the RSV resurgence in 2021, its marginally increased size relative to previous seasons and its decline by January 2022 suggest a stronger dependence of infection susceptibility on age-related factors, as well as a weaker effect of seasonality and a higher baseline transmissibility. The pattern of resurgence has been complicated by contact levels still not back to pre-pandemic levels. Further fitting of RSV resurgence in multiple countries incorporating data on contact patterns will be needed to further narrow down these parameters and to better predict the pathogen's future trajectory, planning for a potential expansion of new immunisation products against RSV in the coming years.

Interactions Between Severe Acute Respiratory Syndrome Coronavirus 2 Replication and Major Respiratory Viruses in Human Nasal Epithelium

The emergence of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), along with extensive nonpharmacological interventions, have profoundly altered the epidemiology of major respiratory viruses. Some studies have described virus-virus interactions, particularly manifested by viral interference mechanisms at different scales. However, our knowledge of the interactions between SARS-CoV-2 and other respiratory viruses remains incomplete. Here, we studied the interactions between SARS-CoV-2 and several respiratory viruses (influenza, respiratory syncytial virus, human metapneumovirus, and human rhinovirus) in a reconstituted human epithelial airway model, exploring different scenarios affecting the sequence and timing of coinfections. We show that the virus type and sequence of infections are key factors in virus-virus interactions, the primary infection having a determinant role in the immune response to the secondary infection.

Prevalence of SARS-CoV-2 positivity in infants with bronchiolitis: a multicentre international study

BACKGROUND

Bronchiolitis is the leading acute respiratory tract infection in infants during the winter season. Since the beginning of the SARS-CoV-2 pandemic, a reduction in the number of bronchiolitis diagnoses has been registered.

OBJECTIVE

The present study aimed to describe the incidence and clinical features of bronchiolitis during the 2020-2021 winter season in a large cohort of children in Europe and Israel, and to clarify the role of SARS-CoV-2.

SETTING, PATIENTS, INTERVENTIONS

We conducted a multicentre observational cross-sectional study in 23 paediatric emergency departments in Europe and Israel. Clinical and demographic data about all the cases of infants diagnosed with bronchiolitis from 1 October 2020 to 30 April 2021 were collected. For each enrolled patient, diagnostic tests, treatments and outcomes were reported.

MAIN OUTCOME MEASURES

The main outcome was the prevalence of SARS-CoV-2-positive bronchiolitis.

RESULTS

Three hundred and fourteen infants received a diagnosis of bronchiolitis during the study period. Among 535 infants who tested positive for SARS-CoV-2, 16 (3%) had bronchiolitis. Median age, male sex predominance, weight, history of prematurity and presence of comorbidities did not differ between the SARS-CoV-2-positive and SARS-CoV-2-negative groups. Rhinovirus was the most common involved pathogen, while respiratory syncytial virus (RSV) was detected in one case. SARS-CoV-2 bronchiolitis had a mild clinical course, with one patient receiving oxygen supplementation and none requiring paediatric or neonatal intensive care unit admission.

CONCLUSIONS

During the SARS-CoV-2 pandemic, a marked decrease in the number of bronchiolitis diagnoses and the disappearance of the RSV winter epidemic were observed. SARS-CoV-2-related bronchiolitis was rare and mostly displayed a mild clinical course.

Evaluation of Four Fully Integrated Molecular Assays for the Detection of Respiratory Viruses during the Co-Circulation of SARS-CoV-2, Influenza and RSV

Background: The clinical presentation of viral respiratory infections is unspecific. We assessed the performances of two new RT-PCR, the Idylla™ SARS-CoV-2 and the Idylla™ SARS-CoV2/Flu/RSV, and two isothermal amplification assays, the ID NOW COVID and the ID NOW influenza A & B 2. Methods: The study was conducted in two parts: (i) the Idylla™ assays were assessed using a collection of nasopharyngeal swabs which were positive for various respiratory viruses. (ii) The performances of the four assays were assessed prospectively: all of the symptomatic patients admitted to the emergency department from 10 to 21 December were enrolled. Results: (i) All of the SARS-CoV-2 false negatives with the Idylla™ assays had a Ct value greater than 30 with the reference RT-PCR. No cross-reactivity was identified. (ii) Overall, 218 patients were enrolled. The respective prevalences of SARS-CoV-2, influenza A, and RSV were 19.8%, 4.8%, and 3.2%. All of the assays were 100% specific. The sensitivity of SARS-CoV-2 detection was 97.7%, 82.5%, and 86.3% for the Idylla™ SARS-CoV2, the Idylla™ SARS-CoV2/Flu/RSV, and the ID NOW COVID-19, respectively. For influenza A, it was 90.0% for the Idylla™ SARS-CoV2/Flu/RSV and 80.0% for the ID NOW Influenza. Discussion. All of the assays are suitable for testing patients with respiratory symptoms. False negatives should be considered, and the test should be repeated regarding the context.

SOCIAL LISTENING AND GOOGLE TRENDS AS TOOLS FOR ESTIMATING PUBLIC AWARENESS OF RESPIRATORY SYNCYTIAL VIRUS

Respiratory Syncytial Virus (RSV) imposes a large disease burden on a global level. Public awareness of RSV is important to support preventive interventions. In this study, Google Trends and a social listening tool, Brand24, were compared for measuring changes in public awareness levels of RSV. Google Trends is recommended for future research, as it is more sensitive, cost-free and open access.

Increased risk of severe COVID-19 in hospitalized patients with SARS-CoV-2 Alpha variant infection: a multicentre matched cohort study

BACKGROUND

The impact of the variant of concern (VOC) Alpha on the severity of COVID-19 has been debated. We report our analysis in France.

METHODS

We conducted an exposed/unexposed cohort study with retrospective data collection, comparing patients infected by VOC Alpha to contemporaneous patients infected by historical lineages. Participants were matched on age (± 2.5 years), sex and region of hospitalization. The primary endpoint was the proportion of hospitalized participants with severe COVID-19, defined as a WHO-scale > 5 or by the need of a non-rebreather mask, occurring up to day 29 after admission. We used a logistic regression model stratified on each matched pair and accounting for factors known to be associated with the severity of the disease.

RESULTS

We included 650 pairs of patients hospitalized between Jan 1, 2021, and Feb 28, 2021, in 47 hospitals. Median age was 70 years and 61.3% of participants were male. The proportion of participants with comorbidities was high in both groups (85.0% vs 90%, p = 0.004). Infection by VOC Alpha was associated with a higher odds of severe COVID-19 (41.7% vs 38.5%-aOR = 1.33 95% CI [1.03-1.72]).

CONCLUSION

Infection by the VOC Alpha was associated with a higher odds of severe COVID-19.

Off-season RSV epidemics in Australia after easing of COVID-19 restrictions

Human respiratory syncytial virus (RSV) is an important cause of acute respiratory infection with the most severe disease in the young and elderly. Non-pharmaceutical interventions and travel restrictions for controlling COVID-19 have impacted the circulation of most respiratory viruses including RSV globally, particularly in Australia, where during 2020 the normal winter epidemics were notably absent. However, in late 2020, unprecedented widespread RSV outbreaks occurred, beginning in spring, and extending into summer across two widely separated regions of the Australian continent, New South Wales (NSW) and Australian Capital Territory (ACT) in the east, and Western Australia. Through genomic sequencing we reveal a major reduction in RSV genetic diversity following COVID-19 emergence with two genetically distinct RSV-A clades circulating cryptically, likely localised for several months prior to an epidemic surge in cases upon relaxation of COVID-19 control measures. The NSW/ACT clade subsequently spread to the neighbouring state of Victoria and to cause extensive outbreaks and hospitalisations in early 2021. These findings highlight the need for continued surveillance and sequencing of RSV and other respiratory viruses during and after the COVID-19 pandemic, as mitigation measures may disrupt seasonal patterns, causing larger or more severe outbreaks.

Non-pharmaceutical interventions for COVID-19 also reduced incidence of respiratory pathogens such as respiratory syncytial virus (RSV). Here, the authors report the resurgence of RSV in Australia following lifting of some of the restrictions and describe reduction in genetic diversity in circulating clades.

Circulating Trends of Influenza and Other Seasonal Respiratory Viruses among the US Department of Defense Personnel in the United States: Impact of the COVID-19 Pandemic

The objective of this study was to evaluate the impact of the COVID-19 pandemic on the circulation of influenza and other seasonal respiratory viruses in the United States. All data were obtained from the US Department of Defense Global Respiratory Pathogen Surveillance Program over five consecutive respiratory seasons from 2016-2017 through to 2020-2021. A total of 62,476 specimens were tested for seasonal respiratory viruses. The circulating patterns of seasonal respiratory viruses have been greatly altered during the pandemic. The 2019-2020 influenza season terminated earlier compared to the pre-pandemic seasons, and the 2020-2021 influenza season did not occur. Moreover, weekly test positivity rates dramatically decreased for most of the seasonal respiratory viruses from the start of the pandemic through spring 2021. After the easing of non-pharmaceutical interventions (NPIs), circulations of seasonal coronavirus, parainfluenza, and respiratory syncytial virus have returned since spring 2021. High rhinovirus/enterovirus activity was evident throughout the 2020-2021 respiratory season. The findings suggest a strong association between the remarkably changed activity of seasonal respiratory viruses and the implementation of NPIs during the COVID-19 pandemic. The NPIs may serve as an effective public health tool to reduce transmissions of seasonal respiratory viruses.

Identifying the Target Population for Primary Respiratory Syncytial Virus Two-Step Prevention in Infants: Normative Outcome of Hospitalisation Assessment for Newborns (NOHAN)

Background: Respiratory syncytial virus (RSV) is the leading cause of acute respiratory infection- related hospitalisations in infants (RSVh). Most of these infants are younger than 6 months old with no known risk factors. An efficient RSVh prevention program should address both mothers and infants, relying on Non-Pharmaceutical (NPI) and Pharmaceutical Interventions (PI). This study aimed at identifying the target population for these two interventions. Methods: Laboratory-confirmed RSV-infected infants hospitalised during the first 6 months of life were enrolled from the Hospices Civils de Lyon birth cohort (2014 to 2018). Clinical variables related to pregnancy and birth (sex, month of birth, birth weight, gestational age, parity) were used for descriptive epidemiology, multivariate logistic regression, and predictive score development. Results: Overall, 616 cases of RSVh in 45,648 infants were identified. Being born before the epidemic season, prematurity, and multiparity were independent predictors of RSVh. Infants born in January or June to August with prematurity and multiparity, and those born in September or December with only one other risk factor (prematurity or multiparity) were identified as moderate-risk, identifying the mothers as candidates for a first-level NPI prevention program. Infants born in September or December with prematurity and multiparity, and those born in October or November were identified as high-risk, identifying the mothers and infants as candidates for a second-level (NPI and PI) intervention. Conclusions: It is possible to determine predictors of RSVh at birth, allowing early enrollment of the target population in a two-level RSV prevention intervention.

Seasonality of respiratory syncytial virus and its association with meteorological factors in 13 European countries, week 40 2010 to week 39 2019

Background

Respiratory syncytial virus (RSV) is the predominant cause of clinical pneumonia among infants and young children, often peaking during the winter months in temperate regions.

Aim

To describe RSV seasonality in 13 European countries and examine its association with meteorological factors.

Methods

We included weekly RSV seasonality data from 13 European countries between week 40 2010 and week 39 2019. Using local weighted regression method, we modelled weekly RSV activity with meteorological factors using data from the 2010/11 to the 2017/18 season. We predicted the weekly RSV activity of the 2018/19 season across 41 European countries and validated our prediction using empirical data.

Results

All countries had annual wintertime RSV seasons with a longitudinal gradient in RSV onset (Pearson’s correlation coefficient, r = 0.71, 95% CI: 0.60 to 0.80). The RSV season started 3.8 weeks later (95% CI: −0.5 to 8.0) in countries in the eastern vs western parts of Europe, and the duration ranged from 8–18 weeks across seasons and countries. Lower temperature and higher relative humidity were associated with higher RSV activity, with a 14-day lag time. Through external validation, the prediction error in RSV season onset was −2.4 ± 3.2 weeks. Similar longitudinal gradients in RSV onset were predicted by our model for the 2018/19 season (r = 0.45, 95% CI: 0.16 to 0.66).

Conclusion

Meteorological factors, such as temperature and relative humidity, could be used for early warning of RSV season onset. Our findings may inform healthcare services planning and optimisation of RSV immunisation strategies in Europe.