Public health is the science and practice of preventing disease, prolonging life, and promoting physical and mental health, taking into account equitable distribution and efficient use of available resources (modified from Winslow 1920). Public health measures are primarily aimed at maintaining the health of the population and its subgroups. To achieve its goals, public health practice relies on scientific evidence. These include

• the incidence and distribution of disease, the causes of health and disease, and the effectiveness of different interventions to promote health and prevent disease
• Explanations for the socially determined inequality of health
• issues of equity of need and distribution
• the optimal design of a health care system, including issues of training, financing, and distribution of responsibilities
• the appropriate participation of patients and citizens.

The tasks outlined above give rise to a variety of issues in many areas. Public health combines knowledge from different disciplines and sub-disciplines. These include demography, epidemiology, health management, health economics, health education, health policy, health psychology, health sociology, health systems research, medicine, medical anthropology, nursing sciences, public health ethics, law, statistics, health services research and others.