All of the body’s organs and systems have specific functions to perform; illness basically results from the failure of any of them to function normally. Illnesses may be acute, producing severe short-lived symptoms, as in influenza; chronic, with symptoms that are prolonged, as in arthritis; or recurrent, as in malaria or various allergies. Good health is ensured not only by avoiding disease, but also by preventing illness through general health tare, hygiene, or such specific methods as vaccination, and by strengthening the body’s natural defenses through diet, exercise, and avoidance of stress.
Causes of illness
Illness usually results from a combination of factors, such as the coincidence of an infection and low natural resistance. This is not always the case, however for example, hereditary and congenital disorders originate before birth.
Congenital disorders affect the developing embryo and may be caused by chromosomal abnormalities or cellular damage. The best known examples include cleft palate and Down syndrome. Embryonic development may be seriously affected by diseases such as rubella. If contracted by the mother in the early stages of pregnancy, rubella can cause abnormalities in the child’s heart, eyes, and ears. Defects of the brain and spinal cord have been linked to vitamin deficiencies. Certain drugs taken by the mother during pregnancy may also result in congenital disorders. Because of this, a pregnant woman should not take any drugs without medical supervision.
After birth, a person’s health is influenced by various external factors. Good health depends, to a great extent, on adequate nutrition and maintenance. Vitamins and minerals are essential for the proper working of the body and their lack may give rise to various deficiency disorders. For example, insufficient iron, needed to make hemoglobin, may result in anemia. And lack of vitamin D is the cause of rickets, a bone disorder uncommon in industrialized nations but only too common in underdeveloped countries.
The best-known causes of illness are living organisms, which range from microscopic viruses and bacteria to larger parasites such as tapeworms. Viruses attack the cell structure of the body. The HIV virus, which causes AIDS, infects certain white blood cells and severely damages the body’s immune system. Other viral diseases include influenza, mumps, poliomyelitis, rabies, and herpes. Bacteria cause disease by producing poisons (toxins), or enzymes, which harm living cells. Bacterial infections include pneumonia, tetanus, and pertussis (whooping cough). Other pathogenic organisms that affect the body include various protozoa, such as amebas, which cause a form of dysentery, and fungi, which cause disorders such as athlete’s foot.
Normal body tissue has the ability to repair itself, but with aging, this mechanism becomes less efficient and may gradually give way to degenerative disorders. Arteriosclerosis, or hardening of the arteries, is one of the most significant of these. Causing reduced blood flow, it can lead to vascular thrombosis (clot in a blood vessel) and coronary heart disease.
Tumors and cancers stand in their own category and are the result of abnormal cellular growth. Many tumors are benign they develop slowly and do not spread but, if located in delicate areas, such as the brain or spinal column, may cause damage by pressing against sensitive tissues. Cancers, in contrast, are malignant tumors caused by cell mutation resulting in abnormal cell growth. They can spread rapidly and cause death by destroying healthy tissue.
As little as 100 years ago, four out of ten babies failed to reach adulthood. Today, life expectancy in the Western world is approximately 80 years. There are many reasons for this dramatic improvement, among them rising living standards in housing, nutrition, working environment, and sanitation, which have removed many of the conditions in which disease once thrived. Medical advances also have played a large part. Some of the most significant contributions to present-day health include a greater understanding of the causes of illness, the use of preventive measures such as vaccination programs, major advances in surgery, and the development of antibiotics and other drugs. As a result of these advances, infectious diseases, such as smallpox and poliomyelitis, have been eradicated in many parts of the world, and a person’s chance of a long and healthy life is better than ever before.
Health and society
Illness may not just be a question of the failure of one of the body systems. Often it is also
closely tied to climatic, social, and environmental factors. Although many infectious diseases have been eradicated in the Western world, most are still common in the Third World, that is, in developing countries, where malnutrition and poverty combine to perpetuate high levels of infant mortality and low life expectancy.
Ironically, the material benefits of improved social living in the Western world have themselves created new health problems. As traditional killers have disappeared, new ones have taken their place. Heart disease and cancers, once little known, are now common and account for a large proportion of all deaths.
Today it is known that such diseases of affluence are directly related to diet, sedentary occupations, smoking, and the stresses of twentieth-century living. Medical cures for these illnesses remain elusive, but some of them can be prevented, and current medical views emphasize the importance of healthy diet and regular exercise, and the dangers of stress, smoking, and alcohol. Good health may, ultimately, depend as much on changes in the way we live as on current or future developments in medical science.