‘Superflu’ H3N2 K-Strain: Symptoms, Vaccine Protection and How the New Flu Variant Is Hitting Hospitals This Winter
Published: 9 December 2025 A heavily mutated flu strain — A/H3N2 subclade K, often dubbed the “K-strain” or “superflu” — is now dominating the 2025–26 flu season and driving record levels of illness in parts of the UK and beyond. On Tuesday, new analysis showed