今年，核心毒株变了

Core Viewpoint - The current flu season in China is experiencing a significant rise in activity, primarily driven by the H3N2 subtype, which accounts for over 95% of cases, while H1N1 and B-type influenza viruses are also present in smaller numbers [3][4]. Group 1: Flu Virus Dynamics - The main change in this flu season is the dominance of the H3N2 strain, which has replaced H1N1 as the primary circulating virus [4]. - The H3N2 strain has not seen large-scale outbreaks in the past two years, leading to a general lack of immunity in the population, thus increasing the risk of infection [4]. - Even though the H3N2 subtype name remains the same, the virus undergoes minor antigenic changes each season, making it a "familiar new enemy" for the immune system [4]. Group 2: Flu Season Statistics - In the 2025-2026 flu season (as of November 2025), H3N2 is the absolute dominant strain, while H1N1 was the main strain in the previous season, accounting for over 99% [5]. - The current flu activity is rapidly increasing, with many provinces reaching moderate to high levels of circulation, contrasting with the previous season, which was relatively stable with localized outbreaks [5]. - The high-risk population this season includes children aged 5-14, who are showing a significant increase in cases, whereas the previous season had a more evenly distributed age demographic [5]. Group 3: Antiviral Medications - Oseltamivir and baloxavir marboxil should not be used as long-term preventive medications; oseltamivir is effective only during the treatment period, and improper use may increase the risk of resistance [6][8]. - In special cases, such as households with individuals over 65 years old, oseltamivir may be considered for preventive use if someone in the household is infected [8]. - It is crucial to take antiviral medications within 48 hours of symptom onset to shorten the duration of illness and reduce the risk of severe outcomes [8]. Group 4: Vaccination Recommendations - The 2025 flu vaccine covers the H3N2 strain and has an efficacy rate of 60%-80%, significantly reducing the risk of severe illness even if infection occurs [10].