Medicine, the practice concerned with the maintenance of health and the prevention, alleviation, or cure of disease.
The World Health Organization at its 1978 international conference held in the Soviet Union produced the Alma-Ata Health Declaration, which was designed to serve governments as a basis for planning health care that would reach people at all levels of society. The declaration reaffirmed that.
health, which is a state of complete physical, mental and social well-being, and not merely the absence of disease or infirmity, is a fundamental human right and that the attainment of the highest possible level of health is a most important world-wide social goal whose realization requires the action of many other social and economic sectors in addition to the health sector.

Organization Of Health Services
It is generally the goal of most countries to have their health services organized in such a way to ensure that individuals, families, and communities obtain the maximum benefit from current knowledge and technology available for the promotion, maintenance, and restoration of health. In order to play their part in this process, governments and other agencies are faced with numerous tasks, including the following: (1) They must obtain as much information as is possible on the size, extent, and urgency of their needs; without accurate information, planning can be misdirected. (2) These needs must then be revised against the resources likely to be available in terms of money, manpower, and materials; developing countries may well require external aid to supplement their own resources. (3) Based on their assessments, countries then need to determine realistic objectives and draw up plans. (4) Finally, a process of evaluation needs to be built into the program; the lack of reliable information and accurate assessment can lead to confusion, waste, and inefficiency.

Health services of any nature reflect a number of interrelated characteristics, among which the most obvious, but not necessarily the most important from a national point of view, is the curative function; that is to say, caring for those already ill. Others include special services that deal with particular groups (such as children or pregnant women) and with specific needs such as nutrition or immunization; preventive services, the protection of the health both of individuals and of communities; health education; and, as mentioned above, the collection and analysis of information.

Levels of health care
In the curative domain there are various forms of medical practice. They may be thought of generally as forming a pyramidal structure, with three tiers representing increasing degrees of specialization and technical sophistication but catering to diminishing numbers of patients as they are filtered out of the system at a lower level. Only those patients who require special attention either for diagnosis or treatment should reach the second (advisory) or third (specialized treatment) tiers where the cost per item of service becomes increasingly higher. The first level represents primary health care, or first contact care, at which patients have their initial contact with the health-care system.

Primary health care is an integral part of a country’s health maintenance system, of which it forms the largest and most important part. As described in the declaration of Alma-Ata, primary health care should be “based on practical, scientifically sound and socially acceptable methods and technology made universally accessible to individuals and families in the community through their full participation and at a cost that the community and country can afford to maintain at every stage of their development.” Primary health care in the developed countries is usually the province of a medically qualified physician; in the developing countries first contact care is often provided by nonmedically qualified personnel.

The vast majority of patients can be fully dealt with at the primary level. Those who cannot are referred to the second tier (secondary health care, or the referral services) for the opinion of a consultant with specialized knowledge or for X-ray examinations and special tests. Secondary health care often requires the technology offered by a local or regional hospital. Increasingly, however, the radiological and laboratory services provided by hospitals are available directly to the family doctor, thus improving his service to patients and increasing its range. The third tier of health care, employing specialist services, is offered by institutions such as teaching hospitals and units devoted to the care of particular groups—women, children, patients with mental disorders, and so on. The dramatic differences in the cost of treatment at the various levels is a matter of particular importance in developing countries, where the cost of treatment for patients at the primary health-care level is usually only a small fraction of that at the third level; medical costs at any level in such countries, however, are usually borne by the government.

In the developing countries
The developing countries differ from one another culturally, socially, and economically, but what they have in common is a low average income per person, with large percentages of their populations living at or below the poverty level. Although most have a small elite class, living mainly in the cities, the largest part of their populations live in rural areas. Urban regions in developing and some developed countries in the mid- and late 20th century developed pockets of slums, which were growing because of an influx of rural peoples and immigrants. Slums persisted into the 21st century, though newer, cheaper construction techniques greatly facilitatedaffordable housing, alleviating some housing problems in densely populated places such as New York City and cities in India. Nonetheless, many urban areas are simply overcrowded, which is problematic for maintaining public health. For lack of even the simplest measures, vast numbers of urban and rural poor die each year of preventable and curable diseases, often associated with poor hygiene and sanitation, impure water supplies, infant mortality in Africa was about eight times greater than in Europe. The extension of primary health-care services is therefore a high priority in the developing countries.

The developing countries themselves, lacking the proper resources, have often been unable to generate or implement the plans necessary to provide required services at the village or urban poor level. It has, however, become clear that the system of health care that is appropriate for one country is often unsuitable for another. Research has established that effective health care is related to the special circumstances of the individual country, its people, culture, ideology, and economic and natural resources.
The rising costs of providing health care have influenced a trend, especially among the developing nations, to promote services that employ less highly trained primary health-care personnel who can be distributed more widely in order to reach the largest possible proportion of the community. The principal medical problems to be dealt with in the developing world include undernutrition, infection, gastrointestinal disorders, and respiratory complaints, which themselves may be the result of poverty, ignorance, and poor hygiene. For the most part, these are easy to identify and to treat. Furthermore, preventive measures are usually simple and cheap. Neither treatment nor prevention requires extensive professional training: in most cases they can be dealt with adequately by the “primary health worker,” a term that includes all nonprofessional health personnel.

In the developed countries
Those concerned with providing health care in the developed countries face a different set of problems. The diseases so prevalent in the Third World have, for the most part, been eliminated or are readily treatable. Many of the adverse environmental conditions and public health hazards have been conquered. Social services of varying degrees of adequacy have been provided. Public funds can be called upon to support the cost of medical care, and there are a variety of private insurance plans available to the consumer. Nevertheless, the funds that a government can devote to health care are limited and the cost of modern medicine continues to increase, thus putting adequate medical services beyond the reach of many. Adding to the expense of modern medical practices is the increasing demand for greater funding of health education and preventive measures specifically directed toward the poor.