As winter approaches, health officials in the U.S. and around the world are raising alarms about what could be a challenging 2025-2026 flu season. A mix of evolving virus strains, low vaccination uptake, and early signs of rising flu activity have created what many experts describe as a "perfect storm."A key concern this season is a newly observed variant of influenza A (H3N2), referred to as subclade K, which has sparked warnings from physicians and public-health researchers.