Public health has been defined as "the science and art of preventing disease, prolonging life and promoting human health through organized efforts and informed choices of society, organizations, public and private, communities and individuals". The concept of health takes into account physical, psychological and social well-being. As such, according to the World Health Organization, it is not merely the absence of disease or infirmity.
Public health is an interdisciplinary field. For example, epidemiology, biostatistics and health services are all relevant. Other important subfields include environmental health, community health, behavioral health, health economics, public policy, mental health, occupational safety, gender issues in health, and sexual and reproductive health.