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.