engleski

Rapid spread and evolution of human respiratory syncytial virus ON1 strains in Croatia, 2012-2014.

Human respiratory syncytial virus (HRSV) causes common respiratory tract infections in infants, young children and among the elderly. Variability among strains is responsible for repeated infections and yearly HRSV outbreaks, with major antigenic differences located in the G protein. The molecular epidemiology of HRSV is rather complex as numerous genotypes exist, new genotypes emerge and some previously circulating genotypes appear to become extinct. Rapid spread of a newly introduced ON1 genotype detected first in Canada in 2010, prompted us to investigate genetic variability of this genotype during the first two years (March, 2012 – March, 2014) of its detection in Croatia. Forty-seven samples belonging to this genotype were investigated, by sequencing second hypervariable domain (HVR2) of the G gene. These strains were more diverse at the amino acid level (76.4%), than at the nucleotide level (86.5%), although positive selection of mutations was shown for only one codon, for which high entropy value was calculated, suggesting that amino acid at this position is experiencing frequent substitutions. Even though these sequences spanned a relatively short period of time, four subclades within the ON1 genotype could already be distinguished from maximum clade credibility tree. Mean evolutionary rate was estimated 7.22 × 10−3 substitutions/site/year (95% HPD 5.07 × 10-3 – 1.33 × 10−2), which is similar to rate reported for BA genotype, a group B genotype. The reason for the epidemiological dominance of this genotype still remains to be elucidated. Therefore, these sequences provide data for further geographical and temporal comparative analyses of HRSV and of its evolutionary and epidemiological pathways.

human respiratory syncytial virus ; genetic variability ; molecular epidemiology ; phylogenetic analysis

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