Core Viewpoint - The influenza virus is expected to be the main pathogen for acute respiratory infectious diseases in China during the winter and spring seasons [1][2] Group 1: Current Situation - The overall flu activity level in China has significantly increased, with a higher prevalence in southern regions compared to northern regions [1] - Acute respiratory infectious diseases are on the rise, with influenza virus, rhinovirus, and respiratory syncytial virus identified as the main pathogens [1] Group 2: Public Health Recommendations - The winter and spring seasons are high-risk periods for acute respiratory infectious diseases, and the public is advised to maintain good hygiene practices such as wearing masks, frequent handwashing, and ensuring proper ventilation [1] - Vaccination is highlighted as the most effective and economical means of preventing infectious diseases, and individuals who have not yet received the flu vaccine are encouraged to do so promptly [2]

Core Points - The overall flu activity level in China is rising, with southern regions experiencing higher levels than northern regions [1] - The flu virus is expected to be the main pathogen for acute respiratory infectious diseases this winter and spring [1] - Multiple acute respiratory pathogens are also at risk of spreading alongside the flu [1] Summary by Category Flu Activity - The National Health Commission announced that the flu season has officially begun across the country, with a noticeable increase in flu activity [1] - The flu virus, rhinovirus, and respiratory syncytial virus are identified as the main pathogens for acute respiratory infections [1] Public Health Recommendations - The public is advised to maintain good hygiene practices, such as wearing masks, frequent handwashing, and ensuring proper ventilation [1] - Vaccination is emphasized as the most effective and economical means of preventing infectious diseases, with a recommendation for eligible individuals to get vaccinated against the flu as activity levels rise [1]

Core Viewpoint - The article emphasizes the importance of preventive measures against influenza as the season approaches, highlighting key strategies for individuals and families to maintain health during this period [1]. Group 1: Influenza Overview - Influenza is an acute respiratory infectious disease caused by the influenza virus, which is categorized into four types: A, B, C, and D. The predominant strains currently circulating in China are the H3N2 subtype of type A, along with the Victoria lineage of type B and the H1N1 subtype of type A [2]. Group 2: Transmission and Symptoms - The primary transmission sources of seasonal influenza are infected patients and asymptomatic carriers. The virus spreads mainly through respiratory droplets produced when an infected person talks, sneezes, or coughs. It can also be transmitted through direct or indirect contact with mucous membranes [3]. - Typical symptoms of influenza include fever, headache, muscle and joint pain, with body temperature reaching 39-40°C. Other symptoms may include sore throat, dry cough, nasal congestion, and fatigue [4]. Group 3: High-Risk Groups - Certain populations are at higher risk of developing severe influenza, including infants, pregnant women, the elderly, and individuals with chronic underlying conditions such as heart and lung diseases, diabetes, and immunosuppression [5]. Group 4: Prevention Strategies - A dual prevention strategy of "vaccination + hygiene habits" is recommended. Timely vaccination is the most effective means of preventing influenza, with September to October being the optimal time for vaccination. Good hygiene practices include regular handwashing, using tissues when coughing or sneezing, and maintaining a balanced diet to enhance immunity [6]. Group 5: Safe Environment Practices - To create a safe home and office environment, it is advised to ventilate regularly by opening windows 2-3 times a day for 20-30 minutes, disinfect frequently touched surfaces, and maintain cleanliness by timely disposal of garbage [7][8][9]. Group 6: Precautions for High-Risk Individuals - High-risk individuals should minimize visits to crowded and enclosed public spaces and are advised to wear masks in such environments. It is also recommended to wear masks when visiting hospitals or using public transportation [10]. Group 7: Response to Symptoms - Influenza is generally self-limiting, with healthy individuals recovering within 1 to 2 weeks. However, early medical consultation is advised for persistent high fever, difficulty breathing, or severe symptoms. Patients should rest at home and avoid close contact with others until symptoms subside [12][13].

Core Insights - The report recommends the composition of influenza virus vaccines for the Northern Hemisphere for the 2025-2026 season, based on the WHO's technical consultation meetings held in February and September each year [1][28] - The recommended vaccine components include strains similar to A/Victoria/4897/2022 (H1N1)pdm09, A/Croatia/10136RV/2023 (H3N2), and B/Austria/1359417/2021 (B/Victoria lineage) for trivalent vaccines [30][31] - The report highlights the ongoing global circulation of A(H1N1)pdm09 and A(H3N2) viruses, with specific genetic lineages identified, indicating the need for continuous monitoring and adaptation of vaccine formulations [25][26] Seasonal Influenza Activity - Influenza activity from September 2024 to January 2025 showed a decrease in overall activity compared to the previous season, with variations in dominant viruses across different regions [3][4] - In Africa, influenza activity peaked in December, primarily driven by A(H3N2) detections, while in Asia, A(H1N1)pdm09 was the dominant strain during the reporting period [3][6] - The Americas experienced increased influenza activity starting in November, with A(H1N1)pdm09 and A(H3N2) viruses circulating at similar levels [8] Virus Characteristics and Antigenic Properties - The A(H1N1)pdm09 virus has been identified in various regions, with genetic analysis revealing the presence of lineages 5a.2a and 5a.2a.1, which continue to diversify [14][25] - A(H3N2) viruses predominantly belong to the 2a.3a.1 lineage, with significant mutations observed, particularly in the J.2 subclade [18][26] - The report indicates that B/Victoria lineage viruses are the only circulating B viruses, with all identified strains belonging to the 3a.2 lineage [22][27] Recommendations for Vaccine Composition - For the 2025-2026 Northern Hemisphere season, the WHO recommends specific strains for both egg-based and cell culture-based vaccines, emphasizing the need to exclude B/Yamagata lineage components due to the absence of circulating strains [30][31] - The report underscores the importance of using updated vaccine strains to enhance effectiveness against circulating viruses, as evidenced by serological studies showing good recognition of recent strains by vaccine-induced antibodies [25][27]