The science and practice of protecting and improving the health of a community, as by preventative medicine, health education, control of communicable diseases, application of sanitary measures, and monitoring of environmental hazards. (The American Heritage Dictionary)
The most common and effective public health activities are in the area of primary prevention, which has two main components: health promotion and health protection.
Health promotion includes health education and the fostering of healthy living conditions and life styles. Outreach and activities are most commonly directed toward individuals, families, groups or entire communities. Activities include helping people identify needs, get useful information and resources, and take action to achieve change.
Health protection services and programs control and reduce the exposure of the population to environmental or personal hazards, conditions or factors that may cause health problems. Health protection includes immunizations, infectious disease surveillance and investigations, water purification, sewage treatment, inspection of multiple public use operations such as food service, campgrounds and manufactured home parks.