ABSTRACT
Background: Mitigation measures implemented during the coronavirus disease 2019 (COVID-19) pandemic remarkably reduced the incidence of infectious diseases among children. However, a re-emergence of respiratory syncytial virus (RSV) infection was observed in 2021 in Japan. We compared the clinical characteristics of hospitalized patients with RSV infection before and during COVID-19. Methods: We retrospectively enrolled children aged <6 years who were hospitalized with RSV infection in 18 hospitals and compared their clinical characteristics before (January 2019 to April 2020, 1675 patients) and during COVID-19 (September 2020 to December 2021, 1297 patients). Results: The mean age of patients with RSV infection was significantly higher during COVID-19 than before (17.4 vs 13.7â months, P < .001). Compared with before COVID-19, a 2.6-fold increase in RSV cases in the 2-5 years age group was observed from sentinel surveillance during COVID-19, whereas a 1.2-fold increase was noted in the same age group among hospitalized patients. On average for all patients, consolidation shadows obtained on radiography were less frequently observed (26.1 vs 29.6%, P = .04), and reduced respiratory assistance (42.2% vs 48.7%, P < .001) and hospitalization stay (5.7 vs 6.0 days, P < .001) was required in patients with RSV infection during COVID-19. Conclusions: Coronavirus disease 2019 and social activity restriction caused epidemiological changes in pediatric RSV infections, and a majority of patients with RSV infection aged ≥2 years did not develop severe symptoms requiring hospitalization. The RSV symptoms during the COVID-19 outbreak were equivalent to or milder than in the previous seasons.
ABSTRACT
BACKGROUND: Respiratory syncytial virus (RSV) is the most common cause of bronchiolitis, and in temperate climates, late fall and winter epidemics of bronchiolitis are usually linked to RSV. In recent years in Japan, the RSV infection epidemic has occurred earlier, even during the hot season. This study aimed to evaluate the seasonal variation of RSV-associated hospitalizations over the past decade and the relationship between season and disease severity. METHODS: This was a retrospective single-center study. Hospitalized children were studied between 2011 and 2019. RSV was detected using rapid antigen detection tests. Clinical information was obtained from medical records, and patients were classified by 4 seasons of admission and analyzed for changes over time. RESULTS: Among 3750 children, 945 (25.2%) were RSV-positive. The seasonal proportion of hospitalized children who are RSV-positive showed a peak shift towards summer, with a turning point in 2016. Comparing 2011-2012 and 2018-2019, incidence increased from 6.8% to 46.3% during summer, whereas during fall decreased from 50.0% to 20.7% and decreased from 28.4% to 20.7% during winter ( P < 0.05). A similar trend was observed in the number of children requiring oxygenation in the earlier period; however, after the transition, there was no significant difference between seasons. CONCLUSIONS: Our findings showed that the RSV epidemic shifted to peak during summer until 2016. There was an association between seasonality and severity, such that many younger children were hospitalized during the autumn and winter and required more oxygen; however, after 2016, this difference was no longer observed.
