The European Centre for Disease Prevention and Control (ECDC) has played a pivotal role in the EU's approach to infectious diseases, but its journey toward empowerment has been anything but straightforward. Historically limited by member states' reluctance to relinquish control over public health, the ECDC's mandate was confined to detecting and assessing communicable diseases, with no authority to offer advice on how to manage these risks. This paradox-assessing threats without the power to guide responses-has been a defining feature of the Centre's existence. However, during the Covid-19 pandemic, the ECDC's mandate was expanded, formally ending this contradiction and allowing the agency to take a more active role in public health decision-making. The Paradox of Communicable Diseases Governance in the EU traces the evolving role of the ECDC, highlighting its empowerment despite a restrictive legal framework. Drawing on over two decades of history of the Centre, the book shows how the ECDC navigated the complex landscape of communicable diseases governance. The book offers valuable insights into the dynamics of European health governance, demonstrating how reputation is key in the development of the most limited agencies. It examines the paradox of the ECDC's mandate-assessing health risks without the power to recommend actions-and how, over time, institutional entrepreneurs used the Centre's reputation as a useful resource to redefine its role. Deruelle offers a fresh perspective on the role of bureaucratic reputation in empowering European agencies, showing how, even with limited authority, institutions can shape policy and practice.