Molecular characterization of respiratory syncycial virus during 2015-2016 season in Portugal

Background: Respiratory syncytial virus (RSV) is one of the most frequent and important respiratory viral agent that causes respiratory infection complications in younger children and elderly. RSV has an autumn / winter seasonality. Genetic diversity in both of RSV A and B subtypes increased in last years with the spread of new genotypes. This study aims to describe the genetic variability of RSV during 2015/2016 season in Portugal and correlate the circulating genotypes with detected ones in previous seasons. Will also be evaluated the association between genotype, clinical diagnosis and age. Methods: During 2015/16 winter season, between November/2015 and February/2016, 45 RSV were genetically characterized. RSV positive respiratory samples were collected in two settings: children under 5 years old diagnosed by hospital laboratories from the Portuguese Laboratory Network for the Diagnosis of Influenza Infection, and all age Influenza-like illness (ILI) patients reported by primary care health services and diagnosed by the National Influenza Reference Laboratory. All samples were irreversibly anonymized. Demographic and clinical data were collected. RSV detection was performed by real-time PCR and other biomolecular methods. RSV genotype was assigned by the nucleotide sequence of the hypervariable C-terminal region of the G protein gene and the phylogenetic analysis was performed in MEGA 6.0. Results: From 45 RSV genetically characterized, 31 (69%) were reported by hospitals, patients age ranged from newborn to 4 years old. From these, 25 (81%; 25/31) patients were hospitalized, being the bronchiolitis the most frequent diagnosis. While 14 (31%) RSV cases came from primary care health services, patients age ranged from 3 to 83 and all had a clinical diagnosis of ILI. Were included patients from both genders in equal proportions. RSV A and B co-circulated during 2015/2016 season. Were genetically characterized 21 (47%) RSV A and 24 (53%) RSV B. 90% (19/21) of RSV A clustered in ON1 genotype, the others 2 clustered with NA1 genotype. All RSV B present a BA-like genotype, 70% (17/24) were similar to BA9 and 30% (7/24) clustered with BA10 genotype. Conclusions: During 2015/2016 season was observed a co-circulation of RSVA and RSVB. In present study ON1genotype was predominant in circulation among RSVA, this was also detected as the major RSVA genotype at the global level. Only two RSVA belonged to NA1 genotype. In Portugal, NA1 was in circulation during 2010-2012 period. Undetected since 2012, it seems to reappear during 2015/16 season. All RSVB characterized belonged to BA genotypes, the majority clustered within BA9 genotype. BA10 genotype was also identified in circulation at low frequency. BA9 and BA10 were being found in co-circulation since 2011/12. No association was found between age, clinical diagnosis and RSVA and B genotypes. RSV has an important impact in children in high-risk groups highlighting the need off a continuous RSV surveillance each winter.