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. 2024 Nov 20;14:28792. doi: 10.1038/s41598-024-80457-4

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© The Author(s) 2024

Open Access This article is licensed under a Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International License, which permits any non-commercial use, sharing, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons licence, and indicate if you modified the licensed material. You do not have permission under this licence to share adapted material derived from this article or parts of it. The images or other third party material in this article are included in the article’s Creative Commons licence, unless indicated otherwise in a credit line to the material. If material is not included in the article’s Creative Commons licence and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. To view a copy of this licence, visit http://creativecommons.org/licenses/by-nc-nd/4.0/.

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Fig. 2 — Phylogenetic analyses of HA and NA genes of H1N1 swine influenza virus. (A) Phylogenetic tree of H1N1 HA gene. (B) Phylogenetic tree of the H1N1 NA gene. With reference to previous studies, the strains were classified into four main categories: TR H1N2 (purple), 2009 H1N1 (deep green), CS H1N1 (orange) and EA H1N1 (deep red). Based on the year of isolation of the strains, the strains were classified into three main categories，using the highlight marker: before the introduction of commercial vaccines (green for 2012-2014 and blue for 2015-2017) and after the introduction of commercial vaccines (yellow after 2018). Strains used in animal testing are shown in red and in an expanded graph.