Text B Different Types of Disease

One of the greatest scientific advances in the history of mankind was the demonstration in the 19^th century by Pasteur, Koch, and others that germs, or microbes, cause disease. However, the germ theory no longer suffices to explain the principal deadly diseases that afflict the civilized world – heart disease, cancer, stroke, premature birth. We know that the causes of disease are multiple. We must giveconsideration to the host of the disease, the agent of the disease, and the environment of both.
The agents of disease may be deprivations (like lack of vitamins) or stresses that upset the normal balance and function of the body, as well as invading germs or poisons. Indeed, in the cycle of disease, all these factors are likely to be present.
There are innumerable classifications of disease. A very simple one is the following:
1. Germ diseases, about 80 in number, amounting to the uncontrolled invasion of the body by a disease-producing germ. These are all communicable diseases, transferred directly or indirectlyfrom one host or victim to another. Indirectly is important; some of them, like malaria, are transmitted from man to man by insects. Contagious, or catching diseases are those transmitted by direct contact with the sick person or some immediate discharge from him; tuberculosis and syphilis, for example, are contagious.
2. Degenerative diseases, in which some part of the body wears out, fails to function, or functions improperly. In cancer, for example, the mechanisms regulating cell growth no longer function properly. Cardiovascularenal diseases represent deterioration, with failure of function, of the heart, blood vessels, and kidneys. In diabetes, the pancreas fails to work properly.
3. Psychosomatic diseases, in which the effect of the mind and the emotions on bodily function is a critical and controlling factor in the onset or perpetuation of the disease. Mental illness is the chief entry in this category; but it also includes such conditions as peptic ulcer, hysterical paralysis, and colitis.
Control of disease is effected by removing the agents of disease from the environment (for example, mosquito control), by treating patients who have the disease (for example, contact tracing and treatment of individuals spreading venereal disease), by acquiring specific artificial immunity to a disease (for example, vaccination against smallpox or paralytic polio), and by building up general resistance to disease processes though good food, adequate rest and exercise, and tranquility of spirit.

Diseases can be classified in a number of ways, depending on the information needed by the doctor or scientist. One way to classify diseases is by the population groups they affect or the way they spread. This is called epidemiology, and it is a very important science. Public health officials use epidemiology to study and manage society’s response to disease.

An epidemiologist looks for several types of information about a disease. For example, he may ask if certain diseases appear mostly among children. If so, he may then recommend large-scale immunization programs, such as those used for the measles-mumps-rubella vaccine.

Epidemiologists also look for associations between certain habits and diseases, such as the connection between smoking and lung disease. Epidemiologists also try to predict how likely it is that one or more diseases will occur in an area where the population is affected by a common circumstance, such as untreated drinking water. These predictions are based on mathematical formulas that determine the chance, or probability, of an outcome given particular circumstances.

It should be no surprise that epidemiologists are also concerned with epidemic diseases—that is, diseases that strike many persons or entire populations within a relatively short period. History has seen many devastating epidemics, from the bubonic plague in Europe during the Middle Ages, to the influenza pandemic (global epidemic) of 1918–19, to the AIDS crisis currently gripping much of the world. When a disease stubbornly remains in the same region year after year, it is called an endemic disease. Yellow fever, for instance, is endemic to tropical South America and Africa, prompting many countries to require travelers to and from those regions to present proof of inoculation against the disease.

Diseases are generally defined as either acute or chronic. An acute disease has a quick onset; most run a relatively short course, during which symptoms may be mild or severe. The common cold is a relatively mild acute disease of fairly short duration. SARS, or severe acute respiratory syndrome, also has a quick onset; but unlike a cold, SARS can rapidly become very serious, even fatal. A chronic disease has a slow onset and a long duration that can last for years. Rheumatoid arthritis is an example of a chronic ailment with a very long course. Some diseases, such as bronchitis, have both acute and chronic forms.

Frequently, diseases are classified according to the organ or organ system that has been affected. There are diseases of the respiratory system (pneumonia), cardiovascular system (coronary artery disease), nervous system (multiple sclerosis), and endocrine system (diabetes mellitus), among many others.

Diseases and their associated signs and symptoms are further distinguished by the extent of their spread in the body. A local, or localized, ailment or symptom is confined to a particular site or single organ system, whereas a systemic disease affects the entire body. This is an important factor in treatment. For example, an infected cut may be treated with a topical antibiotic cream if the infection is limited to the site of the injury. If the infection invades deeper tissues and spreads to the bloodstream, the infectious organism can be carried to every organ in the body. To treat this, doctors must prescribe a systemic drug; this is usually an oral or injectable medication that can enter the bloodstream and fight the infection at all affected sites. Not all systemic diseases are infectious, however. Cancer and diabetes mellitus are two examples of noninfectious systemic diseases.

Notes:

premature firth преждевременные роды deterioration ухудшение; повреждение; износ perpetuation of the disease хроническое течение болезни affliction болезнь, недуг mumps паротит эпидемический, свинка rubella краснуха to grip держать в страхе stubbornly упрямо; упорно endemic disease эндемическое заболевание scurvy цинга