Recently, there has been a noticeable increase in Influenza B cases, particularly among children and adolescents. After a decline since mid-November 2025, the number of suspected influenza cases per 1,000 outpatients rose to 40.9 in the second week of 2026, up from 36.4 the previous week. The surge is most prominent in the 7–18 age group, with a significant rise in the detection rate of Influenza B virus. In response, the Korea Disease Control and Prevention Agency (KDCA) is urging the public to adhere to preventive measures such as handwashing and mask-wearing, and recommends vaccination for those who have not yet received it.
According to KDCA’s sentinel surveillance, the proportion of suspected influenza cases was highest among children aged 7–12 (127.2 per 1,000), followed by 13–18 years (97.2), and 1–6 years (51.0). The detection rate of influenza virus in outpatient samples was 33.5% in week 2, with subtype rates of 15.9% for type A and 17.6% for type B. The current epidemic level remains much higher than the seasonal threshold of 9.1. The circulating Influenza B virus closely matches the WHO-recommended vaccine strain, indicating effective vaccine protection, and no antiviral resistance mutations have been detected.
KDCA Commissioner Seungkwan Lim stated, “Influenza B is spreading earlier than usual this year, raising concerns about a renewed surge.” He emphasized that even those previously infected with Influenza A can contract Influenza B, and urged high-risk groups—including seniors over 65, children, and pregnant women—to get vaccinated immediately. He also stressed the importance of hand hygiene, cough etiquette, mask-wearing, and proper ventilation, and called for prompt medical attention and rest for those with symptoms, as well as supportive policies in schools and workplaces.
The KDCA continues to monitor the influenza situation through a multi-layered surveillance system, with updates available on the FluON dashboard at the Infectious Disease Portal. Preventing further spread requires both vaccination and strict adherence to daily preventive practices. Special attention should be given to educating school-aged children and adolescents on these measures, and ensuring timely medical care for symptomatic individuals. The current trend highlights the need for heightened public awareness and proactive prevention efforts across society.
The current Influenza B trend underscores the importance of targeted health education in schools and homes, especially for children and adolescents. Combining vaccination with consistent preventive practices is crucial to preventing outbreaks, particularly among high-risk groups. The KDCA’s real-time surveillance and public dashboards enable early detection and response, supporting community-level containment. Establishing a culture where staying home when sick is normalized will further help curb the spread of respiratory infections.