Epidemiological and genetic characteristics of respiratory syncytial virus infection in children from Hangzhou after the peak of COVID-19

Background: Respiratory syncytial virus (RSV) is one of the main pathogens that causes acute lower respiratory tract infection (ARTI) in infants. During the Coronavirus Disease 2019 (COVID-19) pandemic, although strict interventions have been implemented, RSV infection has not decreased. Objectives: To study the epidemiological and genetic characteristics of RSV circulating in Hangzhou after the peak of COVID-19. Methods: A total of 1225 nasopharyngeal swabs were collected from outpatients with ARTIs from July 2021 to January 2022 in The Children's Hospital, Zhejiang University School of Medicine. Results: A total of 267 (21.79%) of the 1225 samples were RSV positive. There was no gender bias. However, an obvious age preference for infection was observed, and children aged 3-6 years were more susceptible, which was very different from previous RSV pandemic seasons. Phylogenetic analysis of 115 sequenced RSV isolates showed that all the RSV-A viruses belong to the ON1 subtype, which could be clustered into three clusters. While all the RSV-B viruses belong to BA9. Further analysis of the mutations highlights the fixation of ten mutations, which should be given extra attention regarding their biological properties. Conclusion: The incidence of RSV infection in preschool children reported in this study is high. Phylogenetic analysis showed that the subtype A ON1 genotype was the dominant strain in Hangzhou from July 2021 to January 2022.

Automated summary

This study investigated the epidemiological and genetic characteristics of RSV circulating in Hangzhou after the peak of COVID-19. A total of 267 (21.79%) RSV-positive samples were identified out of 1225 collected nasopharyngeal swabs from outpatients with ARTIs. There was no gender bias, but a clear age preference for infection, with children aged 3-6 years being more susceptible. Phylogenetic analysis revealed that the dominant RSV strains belonged to the ON1 genotype for RSV-A and the BA9 genotype for RSV-B. Ten fixed mutations were also identified, highlighting their importance regarding biological properties.