As you will recall from the Module on Health Education, Advocacy and Community Mobilisation, health is defined as a complete state of physical, mental and social well-being and not the mere absence of disease. The term disease refers to a disturbance in the normal functioning of the body and is used interchangeably with ‘illness’. Diseases may be classified as communicable or non-communicable. Communicable diseases are caused by infectious agents that can be transmitted to other people from an infected person, animal or a source in the environment. Communicable diseases constitute the leading cause of health problems in Ethiopia.

Before we describe each communicable disease relevant to Ethiopia in detail in later study sessions, it is important that you first learn about the basic concepts underlying communicable diseases. Understanding these basic concepts will help you a lot, as they form the basis for this Module.

In this first study session, we introduce you to definitions of important terms used in communicable diseases, the types of infectious agents that cause these diseases, the main factors involved in their transmission, and the stages in their natural development. This will help you to understand how measures for the prevention and control of communicable diseases are put into place at several levels of the health system, including in homes and at your Health Post – which is the focus of Study Session 2.