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Predominance of influenza A(H3N2) viruses during the 2016/2017 season in Bulgaria.
J Med Microbiol. 2018 Feb; 67(2):228-239.JM

Abstract

PURPOSE

Influenza viruses are characterised by high variability, which makes them able to cause annual epidemics. The aim of this study is to determine the antigenic and genetic characteristics of influenza viruses circulating in Bulgaria during the 2016/2017 season.

METHODOLOGY

The detection and typing/subtyping of influenza viruses were performed using real time RT-PCR. Results of antigenic characterisation, phylogenetic and amino acid sequence analyses of representative influenza strains are presented herein.

RESULTS

The 2016/2017 season was characterised by an early start, an exclusive dominance of A(H3N2) viruses accounting for 93 % of total influenza virus detections, and a low circulation of A(H1N1)pdm09 (4.2 %) and type B (2.5 %) viruses. The analysed A(H3N2) viruses belonged to subclades 3C.2a (52 %) and 3C.2a1 (48 %); all studied A(H1N1)pdm09 and B/Victoria-lineage viruses belonged to subclades 6B.1 and 1A, respectively. The amino acid sequence analysis of 56 A(H3N2) isolates revealed the presence of substitutions in 18 positions in haemagglutinin (HA) as compared to the A/Hong Kong/4801/2014 vaccine virus, seven of which occurred in four antigenic sites, together with changes in 23 positions in neuraminidase (NA), and a number of substitutions in internal proteins PB2, PB1, PB1-F2, PA, NP and NS1. Despite the many amino acid substitutions, A(H3N2) viruses remained antigenically similar to the vaccine strain. Substitutions in HA and NA sequences of A(H1N1)pdm09 and B/Victoria-lineage strains were also identified, including in antigenic sites.

CONCLUSION

The results of this study confirm the genetic variability of circulating influenza viruses, particularly A(H3N2), and the need for continued antigenic and molecular surveillance.

Authors+Show Affiliations

National Reference Laboratory "Influenza and ARD", National Centre of Infectious and Parasitic Diseases, 44A Stoletov Blvd, 1233 Sofia, Bulgaria.National Reference Laboratory "Influenza and ARD", National Centre of Infectious and Parasitic Diseases, 44A Stoletov Blvd, 1233 Sofia, Bulgaria.National Reference Laboratory "Influenza and ARD", National Centre of Infectious and Parasitic Diseases, 44A Stoletov Blvd, 1233 Sofia, Bulgaria.Paediatric Clinic, University Hospital Alexandrovska, Medical University, 1"Sv. Georgi Sofiiski" Str., 1431 Sofia, Bulgaria.Paediatric Clinic, University Hospital Alexandrovska, Medical University, 1"Sv. Georgi Sofiiski" Str., 1431 Sofia, Bulgaria.National Reference Laboratory "Influenza and ARD", National Centre of Infectious and Parasitic Diseases, 44A Stoletov Blvd, 1233 Sofia, Bulgaria.National Reference Laboratory "Influenza and ARD", National Centre of Infectious and Parasitic Diseases, 44A Stoletov Blvd, 1233 Sofia, Bulgaria.Paediatric Clinic, University Hospital Alexandrovska, Medical University, 1"Sv. Georgi Sofiiski" Str., 1431 Sofia, Bulgaria.

Pub Type(s)

Journal Article

Language

eng

PubMed ID

29297852

Citation

Korsun, Neli, et al. "Predominance of Influenza A(H3N2) Viruses During the 2016/2017 Season in Bulgaria." Journal of Medical Microbiology, vol. 67, no. 2, 2018, pp. 228-239.
Korsun N, Angelova S, Trifonova I, et al. Predominance of influenza A(H3N2) viruses during the 2016/2017 season in Bulgaria. J Med Microbiol. 2018;67(2):228-239.
Korsun, N., Angelova, S., Trifonova, I., Tzotcheva, I., Mileva, S., Voleva, S., Georgieva, I., & Perenovska, P. (2018). Predominance of influenza A(H3N2) viruses during the 2016/2017 season in Bulgaria. Journal of Medical Microbiology, 67(2), 228-239. https://doi.org/10.1099/jmm.0.000668
Korsun N, et al. Predominance of Influenza A(H3N2) Viruses During the 2016/2017 Season in Bulgaria. J Med Microbiol. 2018;67(2):228-239. PubMed PMID: 29297852.
* Article titles in AMA citation format should be in sentence-case
TY - JOUR T1 - Predominance of influenza A(H3N2) viruses during the 2016/2017 season in Bulgaria. AU - Korsun,Neli, AU - Angelova,Svetla, AU - Trifonova,Ivelina, AU - Tzotcheva,Iren, AU - Mileva,Sirma, AU - Voleva,Silvia, AU - Georgieva,Irina, AU - Perenovska,Penka, Y1 - 2018/01/03/ PY - 2018/1/4/pubmed PY - 2018/2/7/medline PY - 2018/1/4/entrez KW - amino acid substitution KW - antigenic and genetic analysis KW - influenza virus SP - 228 EP - 239 JF - Journal of medical microbiology JO - J Med Microbiol VL - 67 IS - 2 N2 - PURPOSE: Influenza viruses are characterised by high variability, which makes them able to cause annual epidemics. The aim of this study is to determine the antigenic and genetic characteristics of influenza viruses circulating in Bulgaria during the 2016/2017 season. METHODOLOGY: The detection and typing/subtyping of influenza viruses were performed using real time RT-PCR. Results of antigenic characterisation, phylogenetic and amino acid sequence analyses of representative influenza strains are presented herein. RESULTS: The 2016/2017 season was characterised by an early start, an exclusive dominance of A(H3N2) viruses accounting for 93 % of total influenza virus detections, and a low circulation of A(H1N1)pdm09 (4.2 %) and type B (2.5 %) viruses. The analysed A(H3N2) viruses belonged to subclades 3C.2a (52 %) and 3C.2a1 (48 %); all studied A(H1N1)pdm09 and B/Victoria-lineage viruses belonged to subclades 6B.1 and 1A, respectively. The amino acid sequence analysis of 56 A(H3N2) isolates revealed the presence of substitutions in 18 positions in haemagglutinin (HA) as compared to the A/Hong Kong/4801/2014 vaccine virus, seven of which occurred in four antigenic sites, together with changes in 23 positions in neuraminidase (NA), and a number of substitutions in internal proteins PB2, PB1, PB1-F2, PA, NP and NS1. Despite the many amino acid substitutions, A(H3N2) viruses remained antigenically similar to the vaccine strain. Substitutions in HA and NA sequences of A(H1N1)pdm09 and B/Victoria-lineage strains were also identified, including in antigenic sites. CONCLUSION: The results of this study confirm the genetic variability of circulating influenza viruses, particularly A(H3N2), and the need for continued antigenic and molecular surveillance. SN - 1473-5644 UR - https://www.unboundmedicine.com/medline/citation/29297852/Predominance_of_influenza_A_H3N2__viruses_during_the_2016/2017_season_in_Bulgaria_ L2 - http://jmm.microbiologyresearch.org/pubmed/content/journal/jmm/10.1099/jmm.0.000668 DB - PRIME DP - Unbound Medicine ER -