Persistence and continuous evolution of the human respiratory syncytial virus in northern Taiwan for two decades.

The study aimed to characterize the molecular epidemiology, phylogenetic relationship, and population dynamics of the G protein gene in clinical respiratory syncytial virus (RSV) strains isolated from northern Taiwan. We analyzed a total of 160 and 116 G protein gene sequences of RSV-A and RSV-B representative strains, respectively, from 804 clinical viral stocks collected between July 2000 and June 2016. Population dynamic patterns of the RSV G protein gene were analyzed using Bayesian inference through the Markov chain Monte Carlo framework. A phylogenetic analysis revealed that RSV-A from Taiwan could be categorized into GA2, GA5, and GA7 lineages. GA2 of RSV-A could be further divided into NA1, NA2, NA4, and ON1 clades. These RSV-A lineages has been replaced over time, whereas RSV-B strains from Taiwan continually evolved from a single lineage with significant time-dependent waves. Four putative positive selection sites were observed in both RSV-A and RSV-B. The Bayesian skyline plot revealed that the local population dynamics of RSV were associated with lineage displacement events. Both circulating subtypes and population dynamics represented a unique local pattern. Our results affirm the necessity of continuing molecular surveillance of RSV to attain a more comprehensive understanding of epidemics.