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H3N2 Dominates Seasonal Flu in China and Russia as Officials Urge Vaccination

Officials characterize the season as typical, stressing protection from the 2025–2026 flu vaccines.

Overview

  • China CDC data show A(H3N2) in 87.1% of recorded flu outbreaks since spring, with activity peaking in late November before easing by mid‑December as the subtype’s share rose above 80%.
  • Russian health officials report the circulating H3N2 matches last year’s strain, with routine seasonal levels, mostly mild to moderate illness, and hospitalizations below 2%.
  • Hong Kong’s summer surge transitioned into a winter season, but health leaders say overall risk is in line with prior years and the city remains safe for travel.
  • Health authorities discourage the term “Hong Kong flu,” noting H3N2 is a long‑standing seasonal virus undergoing antigenic drift; the 2025–2026 vaccines include H3N2 and target the widely detected subclade K.
  • Experts call for continued surveillance, with some noting a theoretical pandemic risk from H3N2 or avian H5N1, even as current data show no unusual severity and high vaccine alignment with circulating strains.