Public health is "the science and art of preventing disease, prolonging life and promoting health through the organized efforts and updated choices of society, organizations, communities and individuals." It is concerned with intimidation to the overall health of a community based on population health analysis. The population in question can be as small as a handful of people or as large as all the inhabitants of several continents. Public health has many sub-fields, but is naturally divided into the categories of epidemiology, biostatistics and health services. Environmental, social and behavioral healths, and occupational health, are also important fields in public health.

The hub of public health involvement is to prevent rather than treat a disease through surveillance of cases and the encouragement of healthy behaviors. In addition to these activities, in many cases treating a bug can be vital to preventing it in others, such as during an outbreak of an infectious disease. Vaccination programs and distribution of condoms are examples of public health measures.