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We report the molecular investigations of a large influenza A(H3N2) outbreak, in a season characterised by sharp increase in influenza admissions since December 2016. Analysis of haemagglutinin (HA) sequences demonstrated co-circulation of multiple clades (3C.3a, 3C.2a and 3C.2a1). Most variants fell into a novel subclade (proposed as 3C.2a2); they possessed four unique amino acid substitutions in the HA protein and loss of a potential glycosylation site. These changes potentially modify the H3N2 strain antigenicity.


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  1. European Centre for Disease Prevention and Control (ECDC). Risk assessment of seasonal influenza, EU/EEA, 2016-2017 – Update, 25 January 2017. Stockholm: ECDC; 2017.
  2. European Centre for Disease Prevention and Control (ECDC). Influenza virus characterisation, summary Europe, September 2016. Stockholm: ECDC; 2016.
  3. National Institute for Health and Welfare. Finland. Influenssa leviää nyt – rokotuksen ehtii ottaa vielä. Helsinki: THL; 2017. Finnish. [Accessed 3 Feb 2017]. Available from: https://www.thl.fi/en/web/infektiotaudit/-/influenssa-leviaa-nyt-rokotuksen-ehtii-ottaa-viela
  4. Säsongsstatistik för influensa 2016/2017. Stockholm: Stockholm Smittskydd; 2017 [Accessed 3 Feb 2017]. Swedish. Available from: http://www.vardgivarguiden.se/globalassets/behandlingsstod/smittskydd/statistik/influensa/influensasasongen-2016-2017.pdf
  5. Watson SJ, Welkers MR, Depledge DP, Coulter E, Breuer JM, de Jong MD, et al. Viral population analysis and minority-variant detection using short read next-generation sequencing. Philos Trans R Soc Lond B Biol Sci. 2013;368(1614):20120205.  https://doi.org/10.1098/rstb.2012.0205  PMID: 23382427 
  6. Hunt M, Gall A, Ong SH, Brener J, Ferns B, Goulder P, et al. IVA: accurate de novo assembly of RNA virus genomes. Bioinformatics. 2015;31(14):2374-6.  https://doi.org/10.1093/bioinformatics/btv120  PMID: 25725497 
  7. Tamura K, Stecher G, Peterson D, Filipski A, Kumar S. MEGA6: Molecular Evolutionary Genetics Analysis version 6.0. Mol Biol Evol. 2013;30(12):2725-9.  https://doi.org/10.1093/molbev/mst197  PMID: 24132122 
  8. European Centre for Disease Prevention and Control (ECDC). Influenza virus characterisation, summary Europe, May2015. Stockholm: ECDC; 2015. Available from: http://ecdc.europa.eu/en/publications/Publications/influenza-virus-characterisation-april-2015.pdf
  9. Wiley DC, Wilson IA, Skehel JJ. Structural identification of the antibody-binding sites of Hong Kong influenza haemagglutinin and their involvement in antigenic variation. Nature. 1981;289(5796):373-8.  https://doi.org/10.1038/289373a0  PMID: 6162101 
  10. Koel BF, Burke DF, Bestebroer TM, van der Vliet S, Zondag GC, Vervaet G, et al. Substitutions near the receptor binding site determine major antigenic change during influenza virus evolution. Science. 2013;342(6161):976-9.  https://doi.org/10.1126/science.1244730  PMID: 24264991 
  11. Yang H, Carney PJ, Chang JC, Guo Z, Villanueva JM, Stevens J. Structure and receptor binding preferences of recombinant human A(H3N2) virus hemagglutinins. Virology. 2015;477:18-31.  https://doi.org/10.1016/j.virol.2014.12.024  PMID: 25617824 
  12. Wilson IA, Cox NJ. Structural basis of immune recognition of influenza virus hemagglutinin. Annu Rev Immunol. 1990;8(1):737-71.  https://doi.org/10.1146/annurev.iy.08.040190.003513  PMID: 2188678 
  13. Kobayashi Y, Suzuki Y. Evidence for N-glycan shielding of antigenic sites during evolution of human influenza A virus hemagglutinin. J Virol. 2012;86(7):3446-51.  https://doi.org/10.1128/JVI.06147-11  PMID: 22258255 
  14. Stucker KM, Schobel SA, Olsen RJ, Hodges HL, Lin X, Halpin RA, et al. Haemagglutinin mutations and glycosylation changes shaped the 2012/13 influenza A(H3N2) epidemic, Houston, Texas. Euro Surveill. 2015;20(18):21122.  https://doi.org/10.2807/1560-7917.ES2015.20.18.21122  PMID: 25990233 

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