THEORIES FOR POSSIBLE PREVENTION OF DISEASES: VIRAL

Viruses are tiny particles that invade the body and cause diseases ranging from the common cold to hepatitis (inflammation of the liver) and AIDS. Depending on the type they can enter the body easily (in the air in the case of influenza) or only with difficulty (in body fluids such as blood and semen in the case of AIDS). Viruses themselves vary in shape and size and in the ease with which they can be isolated and seen.

There are many disease processes of which we are unsure as to the cause, and many scientists feel that these conditions may be caused by viruses that have yet to be isolated; for example, some doctors believe that rheumatoid arthritis and multiple sclerosis are such conditions. The story with MS is very interesting. It is much more common in temperate climates and in certain countries, e.g. UK, Eire and New Zealand. There is also an unequal distribution within a country, the disease being concentrated in the more remote country areas. It was then noted that these were the most heavily used areas for sheep rearing and that there is a disease of sheep called scrapie that has some of the features of multiple sclerosis. Scrapie is known to be caused by a virus. However, despite much hunting, no virus has been found in MS.

Viruses can produce new disease symptoms many years after the original infectious disease. For example, the measles virus can get into the nervous tissue, where it lies dormant; many years later, though, it can cause a disease called sclerosing panencephalitis, a low-grade inflammation of the brain. This delayed effect is due to what is called a slow virus.

It is also known that viruses can cause dementia. An extremely rare condition called Jakob Creutzfeldt disease has been shown to be caused by a virus. The fascinating thing about this condition is that the virus can be passed on to other people, despite the fact that it remains within the nervous system of those affected, i.e. it shouldn't be infectious. Its potential for transmission was noted when the condition was found to have been passed on within a group of cannibals; presumably eating the brain of an infected person was enough to transmit the virus. Modern reports have shown that the virus has been passed on by accidental inoculation - doctors and technicians dealing with cerebrospinal fluid and nervous tissue samples are at special risk. The AIDS virus is the latest to be shown to cause dementia, albeit in a small proportion of sufferers.

It is unlikely that a virus, slow or otherwise, will be isolated as the cause of Alzheimer's dementia. It is more likely that some viruses will be implicated as environmental triggers in the already predisposed person.

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GENERAL HEALTH