RESUMO
Lower respiratory tract infections caused by the human respiratory syncytial virus (HRSV) represent an immense burden of the disease, especially in young children. This study aimed to investigate the evolutionary history of HRSV strains isolated in the Children's Clinical University Hospital (Riga, Latvia) over three consecutive HRSV seasons. Of 207 samples from children hospitalized with lower respiratory tract infections, 88 (42.5%) tested positive for HRSV by RT-PCR. The seasonal activity started and peaked later than the average for the Northern hemisphere. Patients with HRSV lower respiratory tract infection were significantly younger than patients not infected with HRSV. HRSV-A viruses predominated for two consecutive seasons and were followed by an HRSV-B dominant season. Phylogenetic analysis based on glycoprotein G gene partial sequences revealed that viruses of both groups belonged to the worldwide dominant genotypes NA1 (HRSV-A) and BA-IV (HRSV-B). High diversity of this gene was driven only partially by selection pressure, as only two positively selected sites were identified in each group. Two of the HRSV-A isolates in this study contained a 72-nt duplication in the C-terminal end of the G gene (genotype ON1) that was first described in Canada in the 2010-2011 season. Initial spatial and temporal dynamics of this novel genotype were reconstructed by discrete phylogeographic analysis. Fifteen years after acquiring comparable 60-nt duplication in the G gene, genotype BA lineages have replaced all other HRSV-B strains. However, the population size of genotype ON1 plateaued soon and even decreased slightly before the beginning of the 2012-2013 season.
Assuntos
Infecções por Vírus Respiratório Sincicial/epidemiologia , Infecções por Vírus Respiratório Sincicial/virologia , Vírus Sincicial Respiratório Humano/classificação , Vírus Sincicial Respiratório Humano/genética , Fatores Etários , Pré-Escolar , Análise por Conglomerados , Feminino , Variação Genética , Genótipo , Humanos , Lactente , Letônia/epidemiologia , Masculino , Epidemiologia Molecular , Dados de Sequência Molecular , Filogeografia , RNA Viral/genética , Vírus Sincicial Respiratório Humano/isolamento & purificação , Reação em Cadeia da Polimerase Via Transcriptase Reversa , Estações do Ano , Análise de Sequência de DNA , Homologia de SequênciaRESUMO
For the first time, we studied molecular epidemiology of respiratory syncytial virus in hospitalized children in Latvia. During the study period, ten unique group A and three group B strains were identified and assigned to a single genotype within each group-GA2 for group A and BA-IV for group B.