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Liver and alphabet soup.


Although endowed with remarkable regenerative powers, the liver is an organ essential to such a variety of bodily functions that a sick liver can produce a very sick person. Hepatitis--general inflammation of the liver--is thus a disease to be reckoned with. Acute hepatitis is most commonly the result of the infection with one of several viruses, the most common of which have long carried the designations hepatitis A and hepatitis B. A third type has until now been called non-A, non-B hepatitis because it could be diagnosed only after the other two forms had taken ruled out in a given case. After 10 years of waiting for a laboratory test to distinguish it from its two older brothers, hepatitis C has now come into its own, due to an assay for the virus' antibodies developed by scientists at the Chiron Corporation of Emeryville, CA, using generic engineering methods. And now it seems two other strains have reared their ugly heads as well, although not much is known about either one.

Hepatitis A, also called infectious hepatitis because it can be transmitted directly from one person to another, is most commonly the result of exposure to fecally contaminated food or water. Signs of infection usually appear within two to six weeks after exposure, and treatment consists largely of avoiding strenuous exercise, alcohol and other agents toxic to the liver. Recovery is usually complete in one to four months in the otherwise healthy individual. An injection of gamma globulin, together with good personal hygiene, is usually effective in preventing the disease in persons having close personal contact with infectious hepatitis patients and in travelers exposed to poor sanitation conditions.

Hepatitis B, formerly called serum hepatitis, is usually transmitted by blood or blood products infected with the B virus. It is a much more serious disease because of its longer incubation period (during which it can be transmitted by an apparently well person) and the fact that it can also be transmitted by body secretions through oral or sexual contact. It is thus highly prevalent in homosexuals and intravenous drug users and puts at risk anyone in contact with the blood or other secretions of infected persons (for example, medical and laboratory personnel, as well as patients in hemodialysis centers). Hepatits B vaccine is thus recommended for such persons, as well as sexually promiscous travelers to areas of the world where the disease is far more prevalent. Treatment of the disease is, for the most part, unsatisfactory, so prevention is essential.

Hepatitis C is transmitted through broken skin or the mucous membrane, has an incubation period of one to two months, and causes 20 to 40 percent of all hepatitis cases and 90 to 95 percent of cases resulting from blood transfusions. IV drug use accounts for 40 percent of cases, sexual contact 10 percent, and blood transfusions 5 to 10 percent. More than a third of cases result from unidentified sources. Because the virus has onle very recently become identifiable by these new laboratory methods, prevention consists largely of avoiding the sources of the disease. Specific treatment is only now being tested.

And last, but not least, are hepatitis D and hepatitis E to complete the alphabet soup. Hepatitis D, also known as delta hepatitis, thus far seems to occur only in persons concurrently infected by the hepatitis B virus. Because the delta virus that causes delta hepatitis is a defective virus, meaning it cannot replicate on its own, it needs a "helper" virus--i.e., hepatitis B. Combined with the hepatitis B virus, the delta virus can help manufacture new viruses; hence, the delta virus infection is the culprit behind 60 to 80 percent of persons with hepatitis B who eventually develop chronic hepatitis. As might be expected, the greatest risk of delta infection is among those same population groups at highest risk for hepatitis B. As for hepatitis E, not much is known, probably because it is rarely encountered in the U.S. Although it is much like hepatitis A in its transmission and effect, no blood test is yet available for it. the virus can be identified in a stool sample, however.
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Title Annotation:hepatitis viruses
Publication:Medical Update
Date:Dec 1, 1990
Previous Article:Oh, the smell of it!
Next Article:Back to basics.

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