Diseases – Definitions, Types, Examples and Greatest Threats

A condition that blocks the customary function of the body is defined as a disease. There are three categories of diseases.

They are, intrinsic diseases, extrinsic diseases and unknown diseases.

Intrinsic diseases are those, which come from within one’s own body. Some examples of intrinsic diseases are diabetes mellitus (Type 1 and Type 2), hemophilia, goiter, pellagra, rickets, heart murmurs, lupus and rheumatoid arthritis. Intrinsic diseases are not contagious although some, like hemophilia can be inherited.

Extrinsic diseases are those caused by factors that exist outside one’s body. Examples of extrinsic diseases would be bacterial infections such as anthrax, cholera, pertussis, tuberculosis and urinary tract infections. They also include viral infections like, AIDS, dengue fever, hepatitis, influenza, mumps, smallpox and yellow fever. Additionally, there are fungal infections, which include blastomycosis, cryptococcosis and histoplasmosis. Oh yes, let us not forget parasitic infections ranging from cysticercosis to trypanosomiasis. Finally, there are the prion infectious diseases, only discovered in the 1960’s the scientific community is still struggling to understand the disease sufficiently to find a cure. Our knowledge at this point is quite basic. Prions are primarily composed of protein and propagate by folding abnormally, creating thereby, a structure able to convert normal protein into an abnormally structured form. Some chilling examples of these diseases include Alpers syndrome, Bovine spongiform encephalopathy (mad cow disease), and Kuru. All known prion diseases attack the central nervous system and/or brain. All are fatal.

The final category is unknown diseases. This one gets a little confusing. It isn’t necessarily that the disease is unknown, but rather that its cause is unknown. Prime examples of these are Alzheimer’s disease, chronic fatigue syndrome and fibromyalgia.

Although the vast majority of deaths globally are due to extrinsic diseases, that is only true in the developing world. In the developed world, 8 of the top 10 causes of death are intrinsic diseases. This is readily attributable to better nutrition, superior health care, better environmental conditions and longer life expectancy.

Perhaps most frightening are the prion extrinsic diseases. We have a poor understanding of how they are transmitted, how they propagate and more importantly how to cure them. They are robust! They are resistant to ultraviolet light and can be rendered harmless by only the most rigorous sterilization process. In many respects, they are the most insidious, attacking the nervous system and brain; death is slow and painful for the victim and the victim’s family.

As we discussed earlier, this disease was only discovered in the 1960’s, and not even named until 1982. Prion diseases aren’t getting a great deal of attention from the medical researchers, drug manufacturers or the government. Victims do not exist in great numbers.

My fear is, that like AIDS, a prion disease will rear its head in a surprise attack on an unprepared population. Like AIDS, the developing world will likely be the hardest hit. We must focus more attention on this new threat. We must learn from the mistakes of the AIDS outbreak. We must be prepared!



Source of Diseases – Definitions, Types, Examples and Greatest Threats by Winston P. McDonald – author of Diseases – Definitions, Types, Examples and Greatest Threats article

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