Disease/mortality
The great majority of deaths, especially of children and older adults, are caused by some type of disease. In the developing countries of Africa and Asia, infectious and parasitic diseases (including certain respiratory diseases) account for about half of all deaths, the majority occurring among infants and young children. By contrast, this group of diseases account for only one tenth of all deaths in the industrialized countries. Instead, 50 per cent of deaths in these countries are from circulatory diseases and 19 per cent from cancer. All developing countries list diarrhea as one of the most serious problems affecting the health of their children and one of the main reasons for contact with the health system. Dehydration from diarrhea can now be treated quite adequately with low-cost oral rehydration therapy, yet some 4 million children still die from it each year. Six major preventable diseases of childhood— diphtheria, pertussis (whooping cough), neonatal tetanus, poliomyelitis, measles, and tuberculosis— together kill some 4 million children each year and cause disability in 4 million more. These diseases have been selected as targets for immunization in most countries, but some still have not allocated the relatively modest resources needed to provide this protection.
Malaria and tuberculosis remain major public health problems, with improvement in some countries offset by deterioration in others. Malaria is an important cause of child mortality, especially in tropical Africa. Efforts to control the disease have been hampered by the emergence of mosquitoes that are resistant to the more readily available insecticides and of forms of the malaria parasite that are resistant to drugs.
Many infectious and parasitic diseases can be overcome by improvements in environmental and living conditions and other preventive action. In India, where 45 per cent of the national health budget is used for the control of malaria by conventional methods, health officials have taken further steps in some communities by enlisting villagers to carry out new, environmentally safer ways to control malaria-bearing mosquitoes.
Communicable and parasitic diseases have been greatly reduced in the developed countries by improvements in sanitary conditions, nutrition and health services, allowing large decreases in premature deaths and relative growth of the older age groups. This larger aging population, together with the changes in lifestyle in industrialized societies, has contributed to the growing incidence of circulatory system diseases, which are also a cause for concern in developing countries. Diseases of the circulatory system are also estimated to account for 20 per cent of total invalidity in the developed countries. These diseases and cancer are difficult and costly to treat. More emphasis is being placed on prevention through modification of individual behaviour. Cigarette smoking, through its relationship to heart disease, lung cancer and chronic respiratory disease, is considered the most important preventable contributor to mortality in developed countries. The rapidly increasing number of older citizens in all countries will pressure health systems to provide a broader variety of care in hospitals, chronic care facilities, communities and homes, with the goal of enabling the elderly to stay healthy and remain at home or nearby.
Viral and bacterial epidemics are still a threat, especially in view of inadequate surveillance and preventive measures and ecological factors, such as the spread of certain parasites through irrigation water and the rapid international transmission of various diseases, such as avian influenza by airplane passengers. For the present and foreseeable future the AIDS virus is a serious threat, especially in some of the poorer developing countries, as discussed below. Acquired resistance and natural insensitivity of micro- organisms, insects, rodents, and other carriers of disease to available drugs and pesticides have slowed progress in disease reduction and increased the cost of control. Biotechnology is being used to develop a new generation of vaccines and will no doubt be used to develop drugs that target specific organs and cells, reducing unwanted side- effects.
Severe problems associated with cerebral disease or injury affect no less than 2 per cent of most populations, and neurotic and psychosomatic disorders and alcohol- and drug-related problems affect 3 to 7 per cent. More effective methods of prevention and treatment to deal with alcohol and drug abuse may, however, depend as much on the resolution of economic, social and political problems as on progress in medical technology. Severe mental disorders are also increasing with the aging of the population in most industrialized countries, and psycho- geriatric problems are claiming a significant share of resources for health care. World- wide, an estimated 340 to 480 million people are disabled as a consequence of physical, mental or sensory impairment. To the extent that some of these problems may be genetic in origin, advances in genetic research may provide ways to prevent or cure them.