Event-Based Surveillance (EBS) tools monitor online news reports and other unofficial sources with the primary aim to provide timely information to users from health agencies on disease outbreaks occurring worldwide. In this presentation, Sarah Valentin presents the results of our recently pusblished paper which focuses on how outbreak-related information disseminates from a primary source to to a definitive aggregator, an EBS tool. She and her team analysed news items reporting avian influenza outbreaks in birds worldwide between July 2018 and June 2019 and detected by PADI-web and HealthMap. They used the sources cited in the news to trace the path of each outbreak. We built a directed network with nodes representing the sources (characterised by type, specialisation, and geographical focus) and edges representing the flow of information. They calculated the degree as a centrality measure to determine the importance of the nodes in information dissemination. They analysed the role of the sources in early detection (detection of an event before its official notification) to the World Organisation for Animal Health (WOAH) and late detection. A total of 23% and 43% of the avian influenza outbreaks detected by the PADI-web and HealthMap, respectively, were shared on time before their notification. For both tools, national and local veterinary authorities were the primary sources of early detection. The early detection component mainly relied on the dissemination of nationally acknowledged events by online news and press agencies, bypassing international reporting to the WAOH. WOAH was the major secondary source for late detection, occupying a central position between national authorities and disseminator sources, such as online news.