public health, field of medicine and hygiene dealing with the prevention of disease and the promotion of health by government agencies. In the United States, public health authorities are engaged in many activities, including inspection of persons and goods entering the country to determine that they are free of contagious disease. They are empowered to isolate persons with certain diseases and to quarantine such individuals, if necessary, for the public good. Public health officials are responsible for supervising the purity of the water, milk, and food supply as well as the persons who handle these items and the public eating places that dispense them. They are responsible for the good health of animals that supply food and for the extermination of wildlife, rodents, and insects that contribute to disease. Public health authorities are also concerned with the pollution levels in air and water, and must assure the safety of water used for drinking, for swimming, and as a source of sea food. In addition, they collect vital statistics on death rates, birth rates, communicable and chronic diseases, and other indicators of the state of public health.

The duties of carrying out the many services required to keep the population healthy and to prevent serious outbreaks of disease are divided among local, state, and federal government agencies. They provide health officers and nurses for the schools and visiting nurses for the home. They oversee the water supply, the disposal of sewage, the production and distribution of milk, and the proper handling of food in restaurants. Public health agencies impose standards of public health on local communities when needed; they give financial and technical assistance to local communities in time of crisis, such as that caused by epidemics, hurricanes, and floods.

The principal federal health agency in the U.S. today is the Public Health Services division of the Department of Health and Human Services. It consists of five agencies including the National Institutes of Health, its research arm, which conducts extensive research into neurology, blindness, AIDS, immunology, and heart disease. The Centers for Disease Control and Prevention, another agency under the Public Health Service, maintains statistical data on all diseases; it was instrumental in showing the relationship between tampons and toxic shock syndrome, as well as pinpointing the source of Legionnaire's disease to a new water-borne organism. The Food and Drug Administration is the arm charged with assuring the effectiveness and purity of food, drugs, and cosmetics. The Alcohol, Drug Abuse and Mental Health Administration was established by Congress more recently to address substance abuse and mental health problems. To carry out all these activities the public health services employ large numbers of physicians, dentists, veterinarians, laboratory technicians, nurses, sanitary engineers, health educators, psychologists, and social workers (see also Surgeon General, United States).

Because of the frequent and rapid transportation of people and disease vectors by air there has been a growing need for the monitoring of public health on a global level. This is done by the UN's World Health Organization.

Science and art of preventing disease, prolonging life, and promoting health through organized community efforts. These include sanitation, control of contagious infections, hygiene education, early diagnosis and preventive treatment, and adequate living standards. It requires understanding not only of epidemiology, nutrition, and antiseptic practices but also of social science. Historical public health measures included quarantine of leprosy victims in the Middle Ages and efforts to improve sanitation following the 14th-century plague epidemics. Population increases in Europe brought with them increased awareness of infant deaths and a proliferation of hospitals. Britain's Public Health Act of 1848 established a special public health ministry. In the U.S., public health is studied and coordinated on a national level by the Centers for Disease Control and Prevention; internationally, the World Health Organization plays an equivalent role.

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