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Abstract

In Australia and New Zealand, late outbreaks of an A(H3N2) variant virus termed subclade K extended the 2025 influenza season. Subclade K viruses were genetically and antigenically distinct from the 2025 vaccine A(H3N2) strain A/Croatia/10136RV/2023 (H3N2)-like virus and previously circulating subclade J viruses. Subclade K viruses have since been detected in over 34 countries and appear to have spread globally, except in South America. It is thus likely that they will further expand during the northern hemisphere winter 2025/26 season.

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A corrected article has been published for this content:
Erratum for Euro Surveill. 2025;30(49)
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/content/10.2807/1560-7917.ES.2025.30.49.2500894
2025-12-11
2026-01-16
/content/10.2807/1560-7917.ES.2025.30.49.2500894
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References

  1. Liang Y, Sun Z, Hua W, Li D, Han L, Liu J, et al. Spatiotemporal effects of meteorological conditions on global influenza peaks. Environ Res. 2023;231(Pt 2):116171.  https://doi.org/10.1016/j.envres.2023.116171  PMID: 37230217 
  2. Han AX, de Jong SPJ, Russell CA. Co-evolution of immunity and seasonal influenza viruses. Nat Rev Microbiol. 2023;21(12):805-17.  https://doi.org/10.1038/s41579-023-00945-8  PMID: 37532870 
  3. Kakoullis L, Steffen R, Osterhaus A, Goeijenbier M, Rao SR, Koiso S, et al. Influenza: seasonality and travel-related considerations. J Travel Med. 2023;30(5):taad10202.  https://doi.org/10.1093/jtm/taad102  PMID: 37535890 
  4. National Notifiable Disease Surveillance System (NNDSS). Canberra: NNDSS. [Accessed 21 Nov 2025]. Available from: https://nindss.health.gov.au/pbi-dashboard/
  5. New Zealand Institute for Public Health and Forensic Science (PHF Science). Laboratory-based virology weekly report - 2025 Week 45. Porirua: PHF Science; 13 Nov 2025. [Accessed 21 Nov 2025]. Available from: https://www.phfscience.nz/digital-library/laboratory-based-virology-weekly-report-2025-week-45/
  6. Australian Respiratory Surveillance Reports. [Accessed 21 Nov 2025]. Available from: https://www.health.gov.au/resources/collections/arsr?language=en
  7. WHO FluNet. Virus detections by subtype reported to FluNet. Geneva: World Health Organization. [Accessed 21 Nov 2025]. Available from: https://worldhealthorg.shinyapps.io/flunetchart/
  8. Nextstrain. Real-time tracking of influenza A/H3N2 evolution. [Accessed 21 Nov 2025]. Available from: https://nextstrain.org/seasonal-flu/h3n2/ha/2y
  9. Nextclade. [Accessed 21 Nov 2025]. Nextstrain. Available from: https://clades.nextstrain.org/
  10. GISAID EpiFlu. [Accessed 21 Nov 2025]. Available from: https://gisaid.org/
  11. Patterson Ross Z, Komadina N, Deng YM, Spirason N, Kelly HA, Sullivan SG, et al. Inter-Seasonal Influenza is Characterized by Extended Virus Transmission and Persistence. PLoS Pathog. 2015;11(6):e1004991.  https://doi.org/10.1371/journal.ppat.1004991  PMID: 26107631 
  12. World Health Organization (WHO). Addendum to the recommended composition of influenza virus vaccines for use in the 2019-2020 northern hemisphere influenza season. Geneva: WHO; 21 Mar 2019. [Accessed 21 Nov 2025]. Available from: https://cdn.who.int/media/docs/default-source/influenza/who-influenza-recommendations/vcm-northern-hemisphere-recommendation-2019-2020/201902-recommendation-addendum.pdf?sfvrsn = cb164a4b_13
  13. World Health Organization. Addendum to the recommended composition of influenza virus vaccines for use in the 2003–2004 influenza season. Wkly Epidemiol Rec. 2003;78(11):77. PMID: 12674025 
  14. Centers for Disease Control and Prevention (CDC). Treating Flu with Antiviral Drugs. Atlanta: CDC. 20 Nov 2025. [Accessed 21 Nov 2025]. Available from: https://www.cdc.gov/flu/treatment/antiviral-drugs.html
  15. Kirsebom FC, Thompson C, Talts T, Kele B, Whitaker HJ, Andrews N, et al. Early influenza virus characterisation and vaccine effectiveness in England in autumn 2025, a period dominated by influenza A(H3N2) subclade K. Euro Surveill. 2025;30(46):2500854. PMID: 41267661 
Extended influenza seasons in Australia and New Zealand in 2025 due to the emergence of influenza A(H3N2) subclade K viruses
<p class="citation"> <span>Citation style for this article:</span> <span class="meta-value authors"> <a href="/search?value1=Clyde+Dapat&option1=author&noRedirect=true" class="nonDisambigAuthorLink">Dapat Clyde</a>, <a href="/search?value1=Heidi+Peck&option1=author&noRedirect=true" class="nonDisambigAuthorLink">Peck Heidi</a>, <a href="/search?value1=Lauren+Jelley&option1=author&noRedirect=true" class="nonDisambigAuthorLink">Jelley Lauren</a>, <a href="/search?value1=Tanya+Diefenbach-Elstob&option1=author&noRedirect=true" class="nonDisambigAuthorLink">Diefenbach-Elstob Tanya</a>, <a href="/search?value1=Tegan+Slater&option1=author&noRedirect=true" class="nonDisambigAuthorLink">Slater Tegan</a>, <a href="/search?value1=Saira+Hussain&option1=author&noRedirect=true" class="nonDisambigAuthorLink">Hussain Saira</a>, <a href="/search?value1=Phillip+Britton&option1=author&noRedirect=true" class="nonDisambigAuthorLink">Britton Phillip</a>, <a href="/search?value1=Allen+C.+Cheng&option1=author&noRedirect=true" class="nonDisambigAuthorLink">Cheng Allen C.</a>, <a href="/search?value1=Tim+Wood&option1=author&noRedirect=true" class="nonDisambigAuthorLink">Wood Tim</a>, <a href="/search?value1=Annaleise+Howard-Jones&option1=author&noRedirect=true" class="nonDisambigAuthorLink">Howard-Jones Annaleise</a>, <a href="/search?value1=Yi+Mo+Deng&option1=author&noRedirect=true" class="nonDisambigAuthorLink">Deng Yi Mo</a>, <a href="/search?value1=Jessica+E.+Miller&option1=author&noRedirect=true" class="nonDisambigAuthorLink">Miller Jessica E.</a>, <a href="/search?value1=Q.+Sue+Huang&option1=author&noRedirect=true" class="nonDisambigAuthorLink">Huang Q. Sue</a>, <a href="/search?value1=Ian+G.+Barr&option1=author&noRedirect=true" class="nonDisambigAuthorLink">Barr Ian G.</a></span>. Extended influenza seasons in Australia and New Zealand in 2025 due to the emergence of influenza A(H3N2) subclade K viruses. <a href="/content/ecdc">Euro Surveill.</a> 2025;30(49):pii=2500894. <a href="https://doi.org/10.2807/1560-7917.ES.2025.30.49.2500894" title="doi link" target="_blank">https://doi.org/10.2807/1560-7917.ES.2025.30.49.2500894</a> <span class="ES_Article_citation"> <span class="generated">Received</span>: 28 Nov 2025;&nbsp;&nbsp; <span class="generated">Accepted</span>: 10 Dec 2025 </span> </p>
/content/10.2807/1560-7917.ES.2025.30.49.2500894
/content/10.2807/1560-7917.ES.2025.30.49.2500894
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