Abstract Respiratory syncytial virus (RSV) is a potent pathogen having global distribution. The main purpose of this study was to gain an insight into distribution pattern of the NA1 genotype of group A RSV across the globe together with its evolutionary dynamics. We focused on the second hypervariable region of the G protein gene and used the same for Phylogenetic, Bayesian and Network analyses. Eighteen percent of the samples collected from 500 symptomatic pediatric patients with acute respiratory tract infection (ARI) were found to be positive for RSV during 2011–15 from New Delhi, India. Of these, group B RSV was predominant and clustered into two different genotypes (BA and SAB4). Similarly, group A viruses clustered into two genotypes (NA1 and ON1). The data set from the group A viruses included 543 sequences from 23 different countries including 67 strains from India. The local evolutionary dynamics suggested consistent virus population of NA1 genotype in India during 2009 to 2014. The molecular clock analysis suggested that most recent common ancestor of group A and NA1 genotype have emerged in during the years 1953 and 2000, respectively. The global evolutionary rates of group A viruses and NA1 genotype were estimated to be 3.49 × 10−3 (95% HPD, 2.90–4.17 × 10−3) and 3.56 × 10−3 (95% HPD, 2.91 × 10−3–4.18 × 10−3) substitution/site/year, respectively. Analysis of the NA1 genotype of group A RSV reported during 11 years i.e. from 2004 to 2014 showed its dominance in 21 different countries across the globe reflecting its evolutionary dynamics. The Network analysis showed highly intricate but an inconsistent pattern of haplotypes of NA1 genotype circulating in the world. Present study seems to be first comprehensive attempt on global distribution and evolution of NA1 genotype augmenting the optimism towards the vaccine development. Highlights RSV was detected in 18.6% of the symptomatic patients <5 years of age from New Delhi, India. The tMRCA of RSV-A and NA1 genotype suggested that they emerged in years 1953 and 2000 respectively. Global evolutionary rates of RSV-A and NA1 were 3.49 × 10−3 and 3.56 × 10−3 respectively. BSP showed that the effective population size of the Indian NA1 genotype was constant from 2009 to 14. Network analysis showed highly tangled but an inconsistent pattern of haplotypes of NA1 genotype.
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