Expansion of influenza A(H1N1)pdm09 NA:S247N viruses with reduced susceptibility to oseltamivir, Catalonia, Spain, and in Europe, July to October 2025.
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 (IC50 between 0.82 and 1.63 nM, compared to median IC50 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.
Authors
Saubi Saubi, Andrés Andrés, Prats-Méndez Prats-Méndez, González-Sánchez González-Sánchez, Davtyan Davtyan, Vásquez-Mercado Vásquez-Mercado, Rando Rando, Nadal Nadal, Esperalba Esperalba, Arnedo Arnedo, Vicente Vicente, Balada Balada, Mendioroz Mendioroz, Martín Martín, García-Camuñas García-Camuñas, Vaz Vaz, Najarro Najarro, Bernalte Bernalte, Larrosa Larrosa, Antón Antón,
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