Overview
- WHO officials and national reports say the H3N2 subvariant known as subclade K is now predominant in parts of the U.K., Canada and Japan, and it has been detected in the United States.
- Preliminary analyses from the U.K. suggest vaccines reduce hospitalizations substantially, with about 70–75% protection in children and roughly 30–40% in adults.
- U.S. surveillance has blind spots after a prolonged government shutdown and CDC staffing cuts, leaving the precise share of subclade K in circulation uncertain.
- Local indicators point to acceleration in some regions, with Houston Methodist reporting weekly flu cases roughly doubling since mid‑October while national activity remains low but rising and skewed toward H3N2.
- Flu vaccination is lagging year over year by about 2 million pharmacy doses, raising concerns about hospital capacity in a season already complicated by H3N2 dominance and other outbreaks.