Prevalence and genetic characterisation of respiratory syncytial viruses circulating in Bulgaria during the 2014/15 and 2015/16 winter seasons

Abstract

The respiratory syncytial virus (RSV) is a leading cause of acute respiratory illnesses (ARI) in infants and young children. The objectives of this study were to investigate the RSV circulation among children aged <5 years in Bulgaria, to identify the RSV-A and RSV-B genotypes and to perform an amino acid sequence analysis of second hypervariable region (HVR2) of the G gene. During the 2014/15 and 2015/16 winter seasons, nasopharyngeal specimens of 610 children aged <5 years with ARI were tested using Real Time RT-PCR for influenza viruses, RSV, metapneumovirus, parainfluenza viruses, rhinoviruses and adenoviruses. Viral respiratory pathogens were detected in 429 (70%) out of 610 patients examined and RSV was the most frequently identified virus (26%) followed by influenza A(H1N1)pdm09 virus (14%) (p < .05). RSV was the most prevalent pathogen in patients with bronchiolitis (48%) and pneumonia (38%). In the 2014/15 season, RSV-A dominated slightly (53%), while in the next season RSV-B viruses prevailed more strongly (66%). The phylogenetic analysis based on the G gene indicated that all 21 studied RSV-A strains belonged to the ON1 genotype; the vast majority (96%) of the RSV-B strains were classified into BA9 genotype and only one - into BA10 genotype. All Bulgarian RSV-A and RSV-B sequences contained a 72-nt and a 60-nt duplication in the HVR2, respectively. The study showed the leading role of this pathogen as a causative agent of serious respiratory illnesses in early childhood, year-on-year fluctuations in RSV incidence, a shift from RSV-A to RSV-B subgroup dominance and relatively low genetic divergence in the circulating strains.

Epidemiology and genetic variability of respiratory syncytial virus in Portugal, 2014–2018

“…Nonetheless, a true comparison of RSV prevalence in different geographic areas is difficult to perform taking into account the differences in the study design and, even in our study, prevalence was wide-ranging according to the season. Bronchiolitis and pneumonia were significantly associated with RSV-positive cases among children aged < 5 years, which was consistent with previous studies that found RSV as a major cause of acute LRTI in this age group [12,[38][39][40][41].…”

“…The alignment of the predicted amino acid sequences of strains from BA9, NA1 and ON1 genotypes confirmed the relatively high genetic variability associated with the HVR2. Strains from both of subtypes showed common changes, conserved N-glycosilation sites and subtitutions leading to loss or gain of these sites that had been previously reported [11,40,41,45,46,49,50,[54][55][56][57][58][59]. Within RSV-A strains, the number of substitutions among ON1 strains was higher compared with its NA1 counterparts.…”

“…RSV-A subtype was the most prevalent in the 2015/ 16 season, whereas RSV-B subtype dominated in the next two consecutive seasons (2016/17 and 2017/2018). Periodic shifts (1-3 years) in RSV subtype have been reported all over the world [40]. RSV-A subtype was significantly higher in children younger than 5 years and especially those aged below 6 months, which may be concerning since RSV-A infection has been associated with more severe bronchiolitis and higher disease severity scores [43,44].…”

Systematic Review of the Respiratory Syncytial Virus (RSV) Prevalence, Genotype Distribution, and Seasonality in Children from the Middle East and North Africa (MENA) Region

“…Neutralizing antibodies are secreted against both proteins [ 40 ]. However, based on the genetic variability of the G protein, the RSV A is subdivided into 15 strains (GA1–7, SAA1, NA1–4 CB-A, and ON1–2) [ 41 ], while the RSV B group is subdivided into 24 strains (SAB1–4, BA1–12, GB1–4, GB5/CB1, CBB, and URU1–2) [ 42 , 43 ]. Thus, the infectivity, immunological resistance, and viral genetic drift (spontaneous mutation) may be important in the patterns of seasonal circulation and genetic evolution of RSV genotypes [ 44 ].…”

Dominance of the ON1 Genotype of RSV-A and BA9 Genotype of RSV-B in Respiratory Cases from Jeddah, Saudi Arabia

“…Based on genetic variations in G protein, HRSV is divided into two groups: group A which is categorized into 14 genotypes (GA1 to GA7, SAA1, CB-A, NA1 to NA4 and ON1) and group B which is subdivided into a further 27 genotypes (BA1 to BA12, BA-C, SAB1 to SAB4, GB1 to GB4, URU1 to URU2, CB-B, CB-1, BA-CCB and BA-CCA) [2,4]. The subtype ON1 of RSV-A was first identified in Canada in December of 2010 and was reported to contain a unique duplication of 72 nucleotides in the second hypervariable region of the G gene [5] and it may be spreading rapidly and replacing the NA1 subtype in many countries such as Saudi Arabia, South Korea, Italy, Germany, Bulgaria, Croatia and China [6][7][8][9][10][11][12][13]. A similar duplication was reported in the variable region around 60 nucleotide of the G protein of the BA subtype of RSV-B in 1999 in Argentina [14].…”