In Study Session 40 we considered what public health surveillance means and the activities it involves. In this study session, we will consider the Integrated Disease Surveillance and Response (IDSR) system. IDSR involves carrying out disease surveillance activities using an integrated approach. An integrated approach means that data on all important diseases will be collected, analysed, interpreted and reported in the same way, by the same people who normally submit routine report forms on health-related data. In this study session, we will also consider the case definitions of priority diseases in Ethiopia, and how priority diseases are reported. Proper understanding of IDSR, the case definitions and reporting methods will enable you to identify, register, analyse and report priority diseases quickly and accurately to the proper authorities. These activities are essential in order to ensure that priority diseases in your community can be prevented and controlled.