Molecular epidemiology of Respiratory Syncytial Virus between 2010-2015, in Portugal

Guiomar, Raquel; Cristóvão, Paula; Conde, Patrícia; Pechirra, Pedro

http://hdl.handle.net/10400.18/3570

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Background: Respiratory syncytial virus is one of the major causes of respiratory infection and complications in younger children and elderly. This study has, for the first time, investigated the genetic diversity of RSV A and RSV B detected since 2010, in influenza like illness (ILI) cases reported in the scope of the Portuguese Influenza Surveillance Programme (NISP). Methods: During 2010-2015, nasopharyngeal swabs (NPS) sent to the National Influenza Reference Laboratory from sentinel and non-sentinel network were tested for RSV A and RSV B by real time multiplex RT-PCR. Nucleotide sequence of a fragment of the hypervariable C-terminal region of the G protein gene and the phylogenetic analysis was performed for an half of detected RSV. Results: Over the study period were detected 114 (5.2%) RSV in 2187 tested NPS. Of these 67 (59%) were from subtype A and 47 (41%) from subtype B. Circulation of RSV preceded or was coincident with the influenza epidemic period. RSV A was predominant in each winter with exception for 2014/2015 winter when RSV B was predominantly detected. Of the RSV positive samples, 58 (51%) were successfully sequenced and genetically characterized: 26 (45%) RSV A and 32 (55%) RSV B. RSV A clustered in two genotypes. A majority (n= 22; 85%) belonged to ON1 genotype and 4 (15%) viruses belonged to NA1 genotype. Only ON1 genotype was detected after 2012/2013 season. RSV B clustered in two genotypes: a majority (n=22; 67%) belonged to BA9 genotype and 11 (33%) clustered in BA10 genotype. BA9 genotype was detected over all the study period, although BA10 was only detected in 2012/2013, and 2014/2015 seasons. Conclusion: Our study highlights the importance of RSV in ILI cases, showing a seasonal circulation each winter season during influenza epidemic. RSV accounted for 5.2% of the cases reported in the scope of influenza surveillance, assuming a huge importance in young children and older ones. Molecular data for RSVA revealed co circulation of NA1 and ON1 till 2012, and after this period ON1 was exclusively detected suggesting a strain replacement by this antigenically advantageous genotype. Globally ON1 is also predominantly detected. For RSVB subtype was observed a co circulation of the BA9 and BA10 genotypes. BA derived genotypes, first identified in 1999 in Buenos Aires are predominant in many countries since then.