Genetic diversity and epidemiological features of respiratory syncytial virus, Beijing, 2015-2019: A multicenter and all-age groups study.

Objective: To investigate the genetic variability and the epidemiological features of respiratory syncytial virus (RSV) in Beijing during five consecutive seasons from 2015 to 2019.

Methods: We collected 36,927 samples (ages ranged from 1 day to 101 years old) from cases with acute respiratory tract infections (ARTI) using the Respiratory Pathogens Surveillance System (RPSS) in Beijing, 2015-2019. G gene sequencing and phylogenetic analysis were performed to identify RSV genotypes, clusters, and amino acid (aa) changes.

Results: In total, 764 (2.1%, 764/36927) cases were RSV positive, 52.1% cases were children under 5 years old, and 25.8% were elderly ≥ 60 years old. We obtained 369 sequences of the G gene. ON1 and BA9 were the dominant genotypes in Beijing. Sub-lineage 4 of ON1, which contains four aa substitutions (T113I, N178G, H258Q, and H266L), emerged in 2017 and became the predominant variant in 2018-2019. Sub-lineage 4 of BA9, which contains two aa changes (A131T, T137I), emerged in 2017 and became the predominant variant in 2019. We also observed 10 rarely reported nucleotide deletions in the 3' end of the G gene from five sequences of the ON1 genotype.

Conclusion: With the exception of children < 5 years old, RSV infection mainly occurred in the elderly ≥ 60 years old. Newly emerged sub-lineages have replaced existing sub-lineage over time and become predominant in Beijing. Continued surveillance of the genetic diversity of RSV is necessary.