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Abstract

Between July and October 2025, among the total 117 influenza A(H1N1)pdm09 strains characterised in Catalonia, 20% to 100% per week were carrying the NA:S247N substitution. The mutation, conferring reduced susceptibility to oseltamivir, was phenotypically confirmed (IC between 0.82 and 1.63 nM, compared to median IC of 0.3 nM for susceptible strains). An increased proportion of S247N variants was also observed in sequence data (10,944 sequences) from other parts of Spain and five of 35 submitting countries across Europe.

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/content/10.2807/1560-7917.ES.2025.30.48.2500873
2025-12-04
2026-01-14
/content/10.2807/1560-7917.ES.2025.30.48.2500873
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Expansion of influenza A(H1N1)pdm09 NA:S247N viruses with reduced susceptibility to oseltamivir, Catalonia, Spain, and in Europe, July to October 2025
<p class="citation"> <span>Citation style for this article:</span> <span class="meta-value authors"> <a href="/search?value1=Narc%C3%ADs+Saubi&option1=author&noRedirect=true" class="nonDisambigAuthorLink">Saubi Narcís</a>, <a href="/search?value1=Cristina+Andr%C3%A9s&option1=author&noRedirect=true" class="nonDisambigAuthorLink">Andrés Cristina</a>, <a href="/search?value1=Ignasi+Prats-M%C3%A9ndez&option1=author&noRedirect=true" class="nonDisambigAuthorLink">Prats-Méndez Ignasi</a>, <a href="/search?value1=Alejandra+Gonz%C3%A1lez-S%C3%A1nchez&option1=author&noRedirect=true" class="nonDisambigAuthorLink">González-Sánchez Alejandra</a>, <a href="/search?value1=Alysa+Davtyan&option1=author&noRedirect=true" class="nonDisambigAuthorLink">Davtyan Alysa</a>, <a href="/search?value1=Rodrigo+V%C3%A1squez-Mercado&option1=author&noRedirect=true" class="nonDisambigAuthorLink">Vásquez-Mercado Rodrigo</a>, <a href="/search?value1=Ariadna+Rando&option1=author&noRedirect=true" class="nonDisambigAuthorLink">Rando Ariadna</a>, <a href="/search?value1=Patricia+Nadal&option1=author&noRedirect=true" class="nonDisambigAuthorLink">Nadal Patricia</a>, <a href="/search?value1=Juliana+Esperalba&option1=author&noRedirect=true" class="nonDisambigAuthorLink">Esperalba Juliana</a>, <a href="/search?value1=Maria+Arnedo&option1=author&noRedirect=true" class="nonDisambigAuthorLink">Arnedo Maria</a>, <a href="/search?value1=Marina+Vicente&option1=author&noRedirect=true" class="nonDisambigAuthorLink">Vicente Marina</a>, <a href="/search?value1=Eva+Balada&option1=author&noRedirect=true" class="nonDisambigAuthorLink">Balada Eva</a>, <a href="/search?value1=Jacobo+Mendioroz&option1=author&noRedirect=true" class="nonDisambigAuthorLink">Mendioroz Jacobo</a>, <a href="/search?value1=Mar%C3%ADa+Carmen+Mart%C3%ADn&option1=author&noRedirect=true" class="nonDisambigAuthorLink">Martín María Carmen</a>, <a href="/search?value1=Karen+Garc%C3%ADa-Camu%C3%B1as&option1=author&noRedirect=true" class="nonDisambigAuthorLink">García-Camuñas Karen</a>, <a href="/search?value1=Raquel+Vaz&option1=author&noRedirect=true" class="nonDisambigAuthorLink">Vaz Raquel</a>, <a href="/search?value1=Adri%C3%A0+Najarro&option1=author&noRedirect=true" class="nonDisambigAuthorLink">Najarro Adrià</a>, <a href="/search?value1=Susana+Bernalte&option1=author&noRedirect=true" class="nonDisambigAuthorLink">Bernalte Susana</a>, <a href="/search?value1=Nieves+Larrosa&option1=author&noRedirect=true" class="nonDisambigAuthorLink">Larrosa Nieves</a>, <a href="/search?value1=Andr%C3%A9s+Ant%C3%B3n&option1=author&noRedirect=true" class="nonDisambigAuthorLink">Antón Andrés</a>, <a href="/search?value1=on+behalf+of+the+SIVIC+Infectious+diseases+sentinel+network&option1=author&noRedirect=true" class="nonDisambigAuthorLink">on behalf of the SIVIC Infectious diseases sentinel network</a></span>. Expansion of influenza A(H1N1)pdm09 NA:S247N viruses with reduced susceptibility to oseltamivir, Catalonia, Spain, and in Europe, July to October 2025. <a href="/content/ecdc">Euro Surveill.</a> 2025;30(48):pii=2500873. <a href="https://doi.org/10.2807/1560-7917.ES.2025.30.48.2500873" title="doi link" target="_blank">https://doi.org/10.2807/1560-7917.ES.2025.30.48.2500873</a> <span class="ES_Article_citation"> <span class="generated">Received</span>: 19 Nov 2025;&nbsp;&nbsp; <span class="generated">Accepted</span>: 04 Dec 2025 </span> </p>
/content/10.2807/1560-7917.ES.2025.30.48.2500873
/content/10.2807/1560-7917.ES.2025.30.48.2500873
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