Public health is the science and art of preventing illness and disease and promoting evidence-based health practices with the goal of improving the quality of life. It is concerned with threats to health 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. The dimensions of health can encompass a state of complete physical, mental and social well-being and not merely the absence of disease or infirmity, as defined by the United Nations World Health Organization (WHO). Public health incorporates the interdisciplinary approaches of epidemiology, biostatistics and a vast array of health services. A host of specialists including educators, journalists, researchers, administrators, environmentalists, demographers, social workers, laboratory scientists and more, work to protect the health of the public. Public health professionals serve local, national and international communities in settings such as environmental health, community health, behavioral health, health economics, public policy, insurance and occupational health. Public health is a very rewarding field offering great personal fulfillment in serving others.