In 2023, the Republic of Korea’s Korea Disease Control and Prevention Agency (KDCA) enhanced its event-based surveillance practices by using the World Health Organization’s (WHO) Epidemic Intelligence from Open Sources (EIOS) to actively screen and share information about potential public health threats to the country. This report describes the preliminary assessment of the results of implementing these enhanced event-based surveillance activities from June to October 2023. During this period, 425 (0.4%) events were detected globally by the KDCA from 99 945 media articles, with the highest frequency reported in Asia (185, 43.5%) and North America (81, 19.1%). The most frequently reported diseases or conditions were dengue fever (111, 26.1%) and mpox (32, 7.5%). Eight events were detected early by the KDCA using EIOS before being officially listed on WHO’s Event Information Site (EIS) or in Disease Outbreak News (DON), with an average interval of 20 days (range: 5–41) between the detection date and posting on EIS or DON. Thus, EIOS is efficient in aiding early detection of potential public health threats at the national level. This finding highlights the importance of sustaining international cooperation and support to enhance surveillance capabilities in resource-limited settings and expanding the scope of EIOS, including by incorporating additional sources and sources in additional languages, reducing noise. However, as the current report is based on a descriptive analysis, in the future a systematic evaluation of event-based surveillance using EIOS to identify relevant attributes will need to be conducted.

Objectives: The prevalence of hepatitis B in the Republic of Korea has declined, yet the disease burden persists. After various changes in targets and methods, the national hepatitis B surveillance system now exclusively monitors acute cases. We aimed to assess the alignment of this system with its intended purpose and to recommend improvements supporting the national strategic plan for viral hepatitis management. Methods: This study assessed acute hepatitis B cases reported to the Korean Disease Control and Prevention Agency’s mandatory surveillance system over a 10-year period (2013–2022). It evaluated 5 factors from the Centers for Disease Control and Prevention’s Updated Guidelines for Evaluating Public Health Surveillance Systems: simplicity, positive predictive value, data quality, timeliness, and usefulness. Results: The nonspecific nature of acute hepatitis B symptoms, along with the complexityof diagnostic criteria, indicated a high potential for misreporting. The surveillance system demonstrated a high positive predictive value (94.4%), with data quality and timeliness also rated high. However, data following the onset of the coronavirus disease 2019 pandemicindicate the need for improvement. Moreover, given the relative importance of specificcharacteristics of chronic infectious diseases, only limited interventions are implementable through the current surveillance system. Conclusion The evaluation of the Republic of Korea’s acute hepatitis B surveillance system revealed high positive predictive value, data quality, and timeliness. However, improvements can be made in the misreporting of chronic cases and the system’s usefulness. More accuratereflection of the characteristics of acute hepatitis B cases is essential for better management ofviral hepatitis.