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Produces Disease: Such modified agents may be of three general kinds: (1) a living agent whose pathogenicity has been reduced or attenuated so that it no longer produces disease; (2) a killed preparation of the unaltered agent; and (3) a preparation of a product of the infectious agent. Similarly, in the broader, accepted sense, the term "vaccination" denotes the prophylactic in¬oculation of such materials in order to produce an effective active immunity to the corresponding disease.
Thus, this kind of heart disease has been practically eradicated, al¬though rare cases are still encountered in elderly people. Other endocrine disorders affecting the heart are very rare.
Congenital Heart Disease. With the increasing control of rheumatic heart disease it is probable that congenital cardiovascular disease will soon outstrip it in incidence, and with the increasing control of high blood pressure, congenital heart disease will take second place. An interesting statistical fact is that in the 1920's, T. Duckett Jones and Paul Dudley White found that con¬genital heart disease made up only 1.5% of all of 3,000 patients with Signs or symptoms of heart disease.See Also Brains Of Disease:When it was shown that the brains of diseased animals contained the virus, the way was opened for prevention of the disease. In 1885, Louis Pas¬teur successfully treated a peasant boy, severely bitten by a rabid dog, with a series of injections of a preparation of the virus. In the early 1900's characteristic changes in the nerve cells of in¬fected human beings and animals (Negri bodies, after Adelchi Negri) were first described. This discovery permitted rapid diagnosis of the disease.
Since coronary heart disease has become a leading cause of death in young and middle-aged men in the United States and since there is no really effective cure for it, either surgical or medical, it is essential that the causes of the disease be appraised so that preventive measures can be devised. Studies show that several factors are involved in coronary heart disease, with no single cause being entirely responsible, but the degree of responsibility of each of the many causes is not known.
On The Other Hand See Individ¬ual Disease:IHEUMATISM, roo'ma-tiz'm, a general : for pain in the musculoskeletal system or for abnormal condition of internal or musculo-tal origin that causes such pain. While the term is still in wide popular use, medically it has fallen into relative disuse, gradually being re¬placed by more specific nomenclature for individ¬ual diseases. It is now reserved primarily for that closely related complex of affections that includes rheumatic fever, rheumatic heart disease, and rheu¬matoid arthritis (called Still's disease when it oc¬curs in juveniles).
Finally, one might ask, why is this mutation not eliminated by natural selection? In Africa, where the disease is common, the mutation has been preserved, most likely because individ¬uals with sickle-cell trait, that is, having only one copy of the mutant gene, have an increased resistance to malaria. We still do not know exactly why. Inasmuch as malaria is very prevalent in those districts where the sickle-cell mutant is commonly found, it appears that the mutant offers a selective advantage to those bearing it. |
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