Upsurge of human rhinovirus infection followed by a delayed seasonal respiratory syncytial virus infection in Thai children during the coronavirus pandemic

Epidemiology of respiratory infections during the different levels of non-pharmaceutical interventions

OBJECTIVE

This study aimed to describe epidemiological changes of common respiratory pathogens in children with acute respiratory infections (ARIs) during the different levels of non-pharmaceutical interventions(NPIs).

METHODS

In this retrospective study, we analyzed the prevalence of 12 respiratory pathogens from September 2021 through February 2024 in all inpatients with ARIs admitted to Children's Hospital of Soochow University(SCH). We compared the detection rates of these pathogens at different levels of public NPI measures.

RESULTS

In total, 27,851 respiratory samples were analyzed, including 15,231 boys and 12,620 girls. Under strict NPIs, inpatients with ARIs were more commonly boy and infants (p < 0.01). However, after the discontinuation of NPIs, they were more commonly children over 6 years of age (p < 0.01). Under the strict NPIs, the most detected respiratory pathogen was HRV(23.6%), followed by HRSV(16.0%), HMPV(10.8%) and HPIV(10.4%). But after the abolition strict NPIs, the most common respiratory pathogen was MP(35.9%), followed by HRV(19.7%), HRSV(17.5%) and HPIV (6.6%). Moreover, the number and detection rate of MP and ADV had significantly increased and remained at a high level (P<0.05). In addition, the number of HRSV detection increased and the epidemic season has changed(transitioning from winter to summer), and detection rate of multiple pathogens was more high after the abolition NPIs (P < 0.01).

CONCLUSIONS

Withdrawal of major measures, the disease burden of ARIs in children in Suzhou has sharply increased, mainly attributed to MP, and mixed infections were more common.

Epidemiology of Pediatric Viral Illnesses Before, During, and After the "Tripledemic" Viral Surge

OBJECTIVES

While children represented a small percentage of those hospitalized during the COVID-19 pandemic, there was a surge of pediatric viral-related admissions in the immediate postpandemic viral season. Our study compares the epidemiology and health care utilization of children with acute respiratory infections during the 2022-2023 season to prepandemic and subsequent postpandemic seasons to see if trends persisted.

METHODS

We examined administrative data for children who presented to 2 urban pediatric emergency departments (ED) during 3 periods: 2017-2020 (prepandemic), 2022-2023 (immediate postpandemic), and 2023-2024 (subsequent postpandemic). Outcomes included hospitalization rate for viral-related indications, stepdown/intensive care unit (ICU) admission, and use of advanced respiratory support. Multivariable regression controlled for demographics and specific viruses.

RESULTS

During the study period, there were 65,313 all-cause ED encounters. Compared with prepandemic seasons, viral-related admissions doubled in 2022-2023. In addition to an increase in ED visits, the odds of viral-related admission increased by 98% [adjusted odds ratio (aOR): 1.98; 99.8% CI: 1.75-2.24], odds of stepdown/ICU admission increased by 131% (aOR: 1.31; 99.8% CI: 1.67-3.21) and odds of advanced respiratory support increased by 70% (aOR: 1.70; 99.8% CI: 1.21-2.40). In 2023-2024, the stepdown/ICU admission rate remained the same compared with 2022-2023, and the odds of advanced respiratory support increased (aOR: 1.79, 99.8% CI: 1.22-2.63). Infection with respiratory syncytial virus increased adjusted odds of more advanced care.

CONCLUSIONS

Pediatric ED visits and hospitalization rate decreased in 2023-2024 compared with the postpandemic surge, but the admission rate remained high compared with prepandemic seasons, percent admitted to stepdown/ICU persisted, and the use of advanced respiratory support continued to increase.

Changes in Respiratory Viruses' Activity in Children During the COVID-19 Pandemic: A Systematic Review

Background/Objectives: The impact of the coronavirus disease 2019 (COVID-19) pandemic on health was significant worldwide. The measures adopted to limit the spread of the virus had an indirect effect on the epidemiology of other infectious diseases with similar mechanisms of inter-human transmission. The present literature review analyzed the scenario of pediatric acute respiratory infections in the post-lockdown period compared to the pre-pandemic and lockdown periods. The different patterns of viruses' outbreaks were evaluated according to the type of local COVID-19 restrictive measures and to the type of pathogen. Methods: Relevant scientific literature published between March 2020 and November 2024 was identified by means of electronic keyword searches in the PubMed, Scopus, and Cochrane Library databases. Results: Worldwide implementation of non-pharmacological public health interventions aimed at limiting the COVID-19 pandemic resulted in a measurable effect on the circulation of other common respiratory viruses, significantly affecting their usual seasonality. Most viruses significantly reduced their activity during the lockdown period but returned to or exceeded historical levels after discontinuation of preventive non-pharmacological measures. For many respiratory viruses, particularly respiratory syncytial virus, an off-season increase was reported. Conclusions: The non-pharmacological interventions, which effectively helped limit the COVID-19 pandemic, resulted in relevant epidemiologic changes in most common respiratory viruses. Given the different seasonality and clinical severity observed for some pathogens after lockdown, possible future off-season or more severe epidemics should be expected.

Prevalence and Genetic Diversity of Respiratory Syncytial Virus Reinfections in Young Thai Children, 2016-2023

Although a vaccine for respiratory syncytial virus (RSV) is now available for pregnant women and the elderly, RSV remains a significant cause of respiratory illness in children globally. Reinfections by the same or different RSV subgroups in children residing in the tropics are currently under-studied. Therefore, we examined the patterns of RSV infection and reinfection in Thai children aged ≤ 5 years with respiratory symptoms from 2016 to 2023. Screening of 7710 pediatric respiratory specimens identified 1245 RSV-positive samples (16.1%), mostly from the rainy months (July-November). Interestingly, 74 children experienced two infections, and 6 had three infections. Reinfection by different RSV subgroups occurred in 30 children: 21 were initially infected with RSV-B and later with RSV-A, while 9 had the reverse pattern. Reinfections only by either RSV-A or RSV-B were observed in 22 and 2 children, respectively, with one child infected with RSV-A three times. All RSV-A reinfections belonged to the ON1 genotype, while RSV-B reinfections were BA9. Notably, reinfections across different seasons were observed within homologous pairs. These findings suggest a transitory immunity to natural RSV infection and provide the knowledge that may help optimize pediatric vaccination schedule. Ongoing epidemiological data on RSV are essential in monitoring genotype circulation and vaccine effectiveness.

[Impact of the pandemic on various infectious diseases with different epidemiological patterns of seasonality, transmission and age]

OBJECTIVE

The COVID-19 pandemic has had a strong impact on other infectious diseases. The aim of this paper was to analyze the epidemiological changes that occurred during the pandemic in eight infectious diseases with different epidemiological patterns: influenza, respiratory syncytial virus, rotavirus, pneumococcus, Campylobacter, non-typhoid Salmonella, gonorrhea and herpes zoster.

METHODS

From the Microbiological Surveillance Network, the time series of cases was traced from January 2017 to March 2023. Three periods were distinguished: reference, pandemic and beginning of the post-pandemic. The distribution by age and sex in these periods was analyzed. Incidence rates and rate ratios (RR) were calculated. These RRs and their 95% confidence intervals were estimated overall and by year of age in children under five years of age.

RESULTS

Statistically significant differences were found in the impact that the pandemic had on each of these diseases. Some, after a period of epidemic silence, have revealed an intense post-pandemic rebound. The post-pandemic global RT increased for influenza (2.4), RSV (1.9) and gonorrhea (3.1); rotavirus recovered its pre-pandemic level (1.07); and pneumococcus (0.84), Campylobacter (0.83) and Salmonella (0.60) decreased. In children under 5 years of age, the patterns were specific and heterogeneous for each disease.

CONCLUSIONS

The impact of the pandemic is very different in these diseases. Pediatric and respiratory-transmitted seasonal viral infections are the ones that are most affected, but with different patterns of recovery to normality. Gastrointestinal bacterial infections suffer fewer variations, except for rotavirus. Gonorrhea do not interrupt its increasing trend seen in the pre-pandemic. Shingles show a slight post-pandemic increase. Several diseases with different epidemiological patterns have been studied for a sufficient period to observe how the acute phase of the pandemic emerges.

Incidence of Respiratory Syncytial Virus-Associated Lower Respiratory Tract Illness in Infants in Low- and Middle-Income Regions During the Coronavirus Disease 2019 Pandemic

Background

Incidence data of respiratory syncytial virus-associated lower respiratory tract illness (RSV-LRTI) are sparse in low- and middle-income countries (LMICs). We estimated RSV-LRTI incidence rates (IRs) in infants in LMICs using World Health Organization case definitions.

Methods

This prospective cohort study, conducted in 10 LMICs from May 2019 to October 2021 (largely overlapping with the coronavirus disease 2019 [COVID-19] pandemic), followed infants born to women with low-risk pregnancies for 1 year from birth using active and passive surveillance to detect potential LRTIs, and quantitative reverse-transcription polymerase chain reaction on nasal swabs to detect RSV.

Results

Among 2094 infants, 32 (1.5%) experienced an RSV-LRTI (8 during their first 6 months of life, 24 thereafter). Seventeen (0.8%) infants had severe RSV-LRTI and 168 (8.0%) had all-cause LRTI. IRs (95% confidence intervals [CIs]) of first RSV-LRTI episode were 1.0 (.3-2.3), 0.8 (.3-1.5), and 1.6 (1.1-2.2) per 100 person-years for infants aged 0-2, 0-5, and 0-11 months, respectively. IRs (95% CIs) of the first all-cause LRTI episode were 10.7 (8.1-14.0), 11.7 (9.6-14.0), and 8.7 (7.5-10.2) per 100 person-years, respectively. IRs varied by country (RSV-LRTI: 0.0-8.3, all-cause LRTI: 0.0-49.6 per 100 person-years for 0- to 11-month-olds).

Conclusions

RSV-LRTI IRs in infants in this study were relatively low, likely due to reduced viral circulation caused by COVID-19-related nonpharmaceutical interventions.

Clinical Trials Registration

NCT03614676.

Epidemiology and clinical characteristics of severe acute respiratory infections among hospitalized children under 5 years of age in a tertiary care center in Bangkok, Thailand, 2019-2020

BACKGROUND

Acute respiratory infections (ARIs) are common in children and can range in severity from mild self-limiting illnesses to more severe conditions such as pneumonia and respiratory failure. Data on the epidemiology of viral and bacterial pathogens causing ARIs in children are scarce in this region. This study aimed to investigate the epidemiology and clinical manifestations of pathogens in children aged ≤5 years presenting with severe acute respiratory infection (SARI) in Bangkok, Thailand. The impact of rapid multiplex PCR-based testing on clinical management is also explored.

METHODS

This cross-sectional study enrolled consecutive children aged ≤5 years presenting with SARI at a tertiary care centre in Bangkok, Thailand, between 2019 and 2020. Nasopharyngeal swabs were collected once at admission, and viral and bacterial pathogens were tested using the QIAstat-Dx respiratory panel.

RESULTS

A total of 169 children were enrolled in this study. At least one pathogenic virus was detected in 91.7 % of participants. Based on the final diagnoses made upon discharge, 30.2 % had upper respiratory tract infection, whereas 66.3 % had lower respiratory tract infection. Pneumonia was the most common diagnosis (59.2 %). The most common pathogen identified was rhino/enterovirus (45.2 %), followed by respiratory syncytial virus (31.6 %) and parainfluenza virus (14.2 %). Co-infection was found in 15.4 % and was not associated with increased disease severity.

CONCLUSIONS

This study provides additional insights into the pathogen profiles, clinical diagnosis, and co-infection combinations of ARIs in hospitalized children. This information is useful for diagnosis and treatment of ARIs, as well as implementation of appropriate infection control measures and guidance for future vaccine policy development.

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.

The impact of coronavirus disease 2019 pandemic on bronchiolitis (lower respiratory tract infection) due to respiratory syncytial virus: A systematic review and meta-analysis

The coronavirus disease 2019 (COVID-19) pandemic has changed the epidemiology of respiratory syncytial virus (RSV) infection which accounts for most bronchiolitis and viral pneumonias in infants. This systematic review and meta-analysis aimed to quantitatively assess the effect of the COVID-19 pandemic on RSV-associated bronchiolitis among hospitalized infants. The study protocol was registered in the PROSPERO database (CRD42022314000) and was designed based on Preferred Reporting Items for Systematic Reviews and Meta-analyses guidelines updated in May 2020. The meta-analysis component was modified appropriately to synthesize the pooled proportion of infants having RSV-associated bronchiolitis before the COVID-19 pandemic in 2019 and during the pandemic with 95% confidence interval (CI). We identified and screened 189 articles and systematically reviewed 50 full texts. Eight qualified studies from Europe and China, including 109,186 symptomatic cases of bronchiolitis before the pandemic in 2019 and 61,982 cases in 2020-2021 were pooled by random-effects meta-analysis. The quantitative analysis included laboratory-confirmed RSV infection in 7691 infants with bronchiolitis reported before the pandemic in 2019. Meanwhile, during the pandemic, 4964 bronchiolitis cases were associated with RSV infection. The pooled proportion of RSV-associated bronchiolitis cases before the pandemic in 2019 was 16.74% (95% CI 11.73, 22.43%, 95% prediction interval 0.032, 34.16). The pooled proportion of confirmed RSV cases during the pandemic in 2020/2021 was 19.20% (95% CI 12.01, 27.59%, 95% prediction interval 0.046, 42.35). There was an increase in RSV activity after the relaxation of stringent public health measures during the COVID-19 pandemic.

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.

Machine learning forecasting for COVID-19 pandemic-associated effects on paediatric respiratory infections

OBJECTIVE

The COVID-19 pandemic and subsequent government restrictions have had a major impact on healthcare services and disease transmission, particularly those associated with acute respiratory infection. This study examined non-identifiable routine electronic patient record data from a specialist children's hospital in England, UK, examining the effect of pandemic mitigation measures on seasonal respiratory infection rates compared with forecasts based on open-source, transferable machine learning models.

METHODS

We performed a retrospective longitudinal study of respiratory disorder diagnoses between January 2010 and February 2022. All diagnoses were extracted from routine healthcare activity data and diagnosis rates were calculated for several diagnosis groups. To study changes in diagnoses, seasonal forecast models were fit to prerestriction period data and extrapolated.

RESULTS

Based on 144 704 diagnoses from 31 002 patients, all but two diagnosis groups saw a marked reduction in diagnosis rates during restrictions. We observed 91%, 89%, 72% and 63% reductions in peak diagnoses of 'respiratory syncytial virus', 'influenza', 'acute nasopharyngitis' and 'acute bronchiolitis', respectively. The machine learning predictive model calculated that total diagnoses were reduced by up to 73% (z-score: -26) versus expected during restrictions and increased by up to 27% (z-score: 8) postrestrictions.

CONCLUSIONS

We demonstrate the association between COVID-19 related restrictions and significant reductions in paediatric seasonal respiratory infections. Moreover, while many infection rates have returned to expected levels postrestrictions, others remain supressed or followed atypical winter trends. This study further demonstrates the applicability and efficacy of routine electronic record data and cross-domain time-series forecasting to model, monitor, analyse and address clinically important issues.

SARS-CoV-2 in children and their accompanying caregivers: Implications for testing strategies in resource limited hospitals

Background

Identification of SARS-CoV-2 infected individuals is imperative to prevent hospital transmission, but symptom-based screening may fail to identify asymptomatic/mildly symptomatic infectious children and their caregivers.

Methods

A COVID-19 period prevalence study was conducted between 13 and 26 August 2020 at Tygerberg Hospital, testing all children and their accompanying asymptomatic caregivers after initial symptom screening. One nasopharyngeal swab was submitted for SARS-CoV-2 using real-time reverse-transcription polymerase chain reaction (rRT-PCR). An additional Respiratory Viral 16-multiplex rRT-PCR test was simultaneously done in children presenting with symptoms compatible with possible SARS-CoV-2 infection.

Results

SARS-Co-V 2 RT-PCR tests from 196 children and 116 caregivers were included in the analysis. The SARS-CoV-2 period prevalence in children was 5.6% (11/196) versus 15.5% (18/116) in asymptomatic caregivers (p<0.01). Presenting symptoms did not correlate with SARS-CoV-2 test positivity; children without typical symptoms of SARS-CoV-2 were more likely to be positive than those with typical symptoms (10.2% [10/99] vs 1% [1/97]; p<0.01). Children with typical symptoms (97/196; 49.5%) mainly presented with acute respiratory (68/97; 70.1%), fever (17/97; 17.5%), or gastro-intestinal complaints (12/97; 12.4%); Human Rhinovirus (23/81; 28.4%) and Respiratory Syncytial Virus (18/81; 22.2%) were frequently identified in this group. Children-caregiver pairs' SARS-CoV-2 tests were discordant in 83.3%; 15/18 infected caregivers' children tested negative. Symptom-based COVID-19 screening alone would have missed 90% of the positive children and 100% of asymptomatic but positive caregivers.

Conclusion

Given the poor correlation between SARS-CoV-2 symptoms and RT-PCR test positivity, universal testing of children and their accompanying caregivers should be considered for emergency and inpatient paediatric admissions during high COVID-19 community transmission periods. Universal PPE and optimising ventilation is likely the most effective way to control transmission of respiratory viral infections, including SARS-CoV-2, where universal testing is not feasible. In these settings, repeated point prevalence studies may be useful to inform local testing and cohorting strategies.

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.

Understanding the Potential Drivers for Respiratory Syncytial Virus Rebound During the Coronavirus Disease 2019 Pandemic

Nonpharmaceutical interventions (NPIs) were widely introduced to combat the coronavirus disease 2019 (COVID-19) pandemic. These interventions also likely led to substantially reduced activity of respiratory syncytial virus (RSV). From late 2020, some countries observed out-of-season RSV epidemics. Here, we analyzed the role of NPIs, population mobility, climate, and severe acute respiratory syndrome coronavirus 2 circulation in RSV rebound through a time-to-event analysis across 18 countries. Full (re)opening of schools was associated with an increased risk for RSV rebound (hazard ratio [HR], 23.29 [95% confidence interval {CI}, 1.09-495.84]); every 5°C increase in temperature was associated with a decreased risk (HR, 0.63 [95% CI, .40-.99]). There was an increasing trend in the risk for RSV rebound over time, highlighting the role of increased population susceptibility. No other factors were found to be statistically significant. Further analysis suggests that increasing population susceptibility and full (re)opening of schools could both override the countereffect of high temperatures, which explains the out-of-season RSV epidemics during the COVID-19 pandemic.

Viral infections in hospitalized children in Germany during the COVID-19 pandemic: Association with non-pharmaceutical interventions

BACKGROUND

Non-pharmaceutical interventions (NPI) during the COVID-19 pandemic aimed at prevention of SARS-CoV-2 transmission also influenced transmission of viruses other than SARS-CoV-2. The aim of this study was to describe and compare the burden of common viral respiratory and gastrointestinal infections in children admitted to Berlin University Children's Hospital (BCH) before and during the COVID-19 pandemic at different levels of public NPI measures.

METHODS

In this retrospective study, we analyzed the frequency of detection of common human respiratory and gastrointestinal viruses from January 2016 through January 2022 in all patients admitted to BCH. We compared virus detection before and during the COVID-19 pandemic at different levels of public NPI measures.

RESULTS

The frequency of detection of seasonal enveloped and non-enveloped viruses [Boca-, Corona-, Influenza-, Metapneumo-, Parainfluenza-, Rota-, and Respiratory Syncytial Viruses (RSV)] was diminished during the COVID-19 pandemic, whereas detection rates of non-seasonal viruses (Rhino-/Entero-, and Adenoviruses) were stable during the pandemic. After withdrawal of major NPI measures, we observed an out of season surge of the detection rates of Boca-, Corona-, Parainfluenzaviruses, and RSV. In contrast, no increased detection frequency was observed for Influenza-, Metapneumo-, and Rotaviruses as of January 2022.

CONCLUSION

Corona-, Boca-, Parainfluenzaviruses, and RSV returned as frequently detected pathogens after withdrawal of major NPI measures. The out of season rise might be attributed to an "immune-debt" due to missing contact to viral antigens resulting in waning of population immunity during the COVID-19 pandemic.

Delayed respiratory syncytial virus outbreak in 2020 in Taiwan was correlated with two novel RSV-A genotype ON1 variants

Background

Human respiratory syncytial virus (RSV) is a leading pathogen of acute respiratory tract disease among infants and young children. Compared with previous seasons, RSV outbreaks in Taiwan during the 2020–2021 season were delayed because of COVID‐19 mitigation measures. We conducted this study to determine the association of viral factors with clinical characteristics of preschool children with RSV infection.

Methods

We performed a molecular epidemiology analysis of RSV among inpatient preschool children in Taiwan. In 80 nasopharyngeal samples positive for RSV, we sequenced and analyzed viral genotypes according to patient data. Patients' clinical data were obtained from medical files, and their clinical profiles were compared with those of RSV cases recorded during the 2014–2017 seasons.

Results

Phylogenetic analysis revealed that among the RSV‐positive samples, all RSV strains identified during the 2020–2021 season belonged to the ON1 genotype. Most of the Taiwan ON1 strains were categorized into two well‐supported clusters with distinct G protein amino acid substitution patterns that had never been demonstrated previously. Furthermore, the proportion of cases among children aged >24 months increased (P < 0.001). Compared with patients infected during the 2014–2017 seasons, patients infected during the 2020–2021 season were hospitalized for shorter days from hospital admission to dereference (P = 0.004) and had a greater need for oxygen supplements (P = 0.021) and systemic steroid therapy (P = 0.026).

Conclusion

The delayed 2020–2021 RSV outbreak in Taiwan was caused by two novel RSV ON1.1 variants. How the change in RSV epidemiology affects future RSV outbreaks warrants exploration.