Circulation pattern and genetic variation of human respiratory syncytial virus in China during 2008-2021.

To better understand the circulation pattern and genetic characterization of human respiratory syncytial virus (HRSV) in China during 2008-2021, a total of 3967 HVR2 sequences were obtained from 20 provinces in China for phylogenetic analysis and sequence variation analysis. The results showed that the HRSV subtype presented the prevalence pattern of "ABBAABAABAAABB." Further genotyping identified seven genotypes for HRSVA and nine genotypes for HRSVB. Multiple genotypes of HRSV were cocirculating during 2008-2015, while ON1 and BA9 became the only predominant genotypes for HRSVA and HRSVB, respectively, since 2015. A genotype switch from NA1 to ON1 for HRSVA occurred in approximately 2014, while genotype BA9 of HRSVB had been the predominant genotype for at least 14 years. ON1 strains could be divided into four lineages with no temporal or geographical distribution tendency. In contrast, BA9 strains could be divided into three lineages with noticeable temporal clustering. Sequence variation analysis showed that two ON1 sequences in 2017 had 10 nucleotide deletion and compensatory extension at the C-terminal; 15 BA9 sequences during 2019-2021 had novel insertions between K225 and E226, along with 6 identical amino acid variant sites. This study further enriched the genetic data of HRSV circulating in China and provided an important basis for the development of HRSV vaccines and drugs as well as the formulation of prevention and control strategies.