Infections Caused by HRSV A ON1 Are Predominant among Hospitalized Infants with Bronchiolitis in São Paulo City

Human respiratory syncytial virus is the main cause of respiratory infections in infants. Several HRSV genotypes have been described. Goals. To describe the main genotypes that caused infections in São Paulo (2013–2015) and to analyze their clinical/epidemiological features. Methods. 94 infants (0–6 months) with bronchiolitis were studied. Clinical/epidemiological information was collected; a search for 16 viruses in nasopharyngeal secretion (PCR-real-time and conventional, sequencing, and phylogenetic analyses) was performed. Results. The mean age was 2.4 m; 48% were male. The mean length of hospital stay was 4.4 d (14% in the Intensive Care Unit). The positive rate of respiratory virus was 98.9%; 73 cases (77.6%) were HRSV (76,7% HRSVA). HRSVA formed three clusters: ON1 (n = 34), NA1 (n = 1), and NA2 (n = 4). All HRSVB were found to cluster in the BA genotype (BA9-n = 10; BA10-n = 3). Clinical analyses showed no significant differences between the genotype AON1 and other genotypes. Conclusion. This study showed a high rate of HRSV detection in bronchiolitis. HRSVA ON1, which has recently been described in other countries and has not been identified in previous studies in the southeast region of Brazil, was predominant. The clinical characteristics of the infants that were infected with AON1 were similar to infants with infections by other genotypes.