Current influenza situation in Taiwan — October 2025

Key points AH3N2 is now the dominant influenza strain; influenza activity and severe complications are increasing. Severe complications and mortality predominantly affect adults aged ≥50 years, particularly those ≥65 years. Most H1N1 and B/Victoria isolates remain antigenically matched to vaccine reference strains; AH3N2 shows lower concordance, potentially reducing vaccine effectiveness. Antiviral resistance remains uncommon but present (notably 7% oseltamivir resistance among AH1N1 isolates). Ongoing surveillance, vaccination, and early antiviral therapy in at-risk adults are strongly recommended. Epidemiologic overview Taiwan is experiencing a marked rise in influenza activity, with both the number and proportion of influenza-like illness (ILI) consultations increasing during September–October 2025. The proportion of emergency room visits attributed to ILI has surpassed the epidemic threshold, indicating an active epidemic phase. Laboratory surveillance confirms influenza A, particularly AH3N2, as the predominant circulating strain, overtaking AH1N1 and other respiratory viruses. Laboratory findings and virological surveillance During the 2024–2025 season, Taiwan reported 2,267 cases of influenza with severe complications, including 561...