Nikhil Prasad Fact checked by:Thailand Medical News Team Jan 06, 2026 1 day, 12 hours, 15 minutes ago
Medical News: Spain experienced an intense early flu wave this winter, driven by the new mutated H3N2 subclade K strain, which pushed healthcare systems to the brink with record-high cases in December 2025. The epidemic as yet to peak and a drop in positivity rates could due the long holidays over the New Year with many facilities closed. Hospitals and healthcare professionals are however overwhelmed.
Hospitals across Spain are overwhelmed due to the new mutated H3N2 K Clade Flu strain that is wreaking havoc across the country.
This
Medical News report examines the latest data from the Instituto de Salud Carlos III (ISCIII)'s SiVIRA surveillance system for week 52/2025 (December 22–28, 2025). It shows a decline in flu activity during the Christmas week, likely influenced by reduced consultations and holiday behaviors. Primary care flu positivity dropped to 41.7% from 48.2% the previous week, while estimated flu incidence fell to 239.2 cases per 100,000 inhabitants from 403.9.
The Dominant Strain: H3N2 Subclade K
The A(H3N2) subclade K remains the dominant variant, accounting for 96% of characterized H3N2 viruses (represented by A/Norway/8765/2025-like strains).
This highly transmissible subclade fueled the early surge across Europe and Spain, starting the epidemic weeks ahead of schedule.
Virological surveillance from ISCIII confirms sustained predominance of subclade K, with minor co-circulation of other clades. The strain evades prior immunity. The wave's intensity stemmed from high case volumes affecting the elderly and children.
By week 52, overall acute respiratory infection rates declined slightly to 573.6 per 100,000 inhabitants.
Impact on Hospitals and Healthcare
Hospital pressure eased slightly in late December, with severe acute respiratory infection (IRAG) rates stable at 22.9 per 100,000. Flu-related hospitalizations held steady at around 9.9 per 100,000, while hospital positivity for influenza reached 43.2%.
The earlier peak in weeks 49–51 strained emergency services in regions like Madrid, Catalonia, and Andalucía. Reduced primary care visits during holidays contributed to the observed drop in reported cases. Severity indicators, including pneumonia (19.9%), ICU admissions (4.2%), and mortality (4.6%) since the season start, remained consistent without escalation.
Recommendations and Outlook
Health authorities continue recommending vaccination for high-risk groups, as claims that the current vaccines offer protection against subclade K despite an antigenic drift.
Hygiene measures, mask use in crowded settings, and avoiding contact when symptomatic are key to preventing rebounds. ISCIII surveillance is monitoring for any post-holiday resurgence.
References:
manal_SiVIRA_202552.html">https://docsivira.isciii.es/Informe_semanal_SiVIRA_202552.html
https://cne.isciii.es/en/servicios/enfermedades-transmisibles/enfermedades-a-z/gripe-covid-19-y-otros-virus-respiratorios
For the latest on the flu surge in many geolocations across the world, keep on logging to Thailand
Medical News.
Read Also:
https://www.thailandmedical.news/articles/influenza-or-flu
Share
Tweet
Share
