Presence Of The Hepatitis B Virus example essay topic

Hepatitis is a disorder involving inflammation of the LIVER. Symptoms include loss of appetite, dark urine, fatigue, and sometimes fever. The liver may become enlarged and JAUNDICE may occur, giving the skin a yellow tinge. Hepatitis may be acute or chronic. The acute form can subside after about two months or, rarely, can result in liver failure. Chronic carriers are at risk of lasting liver disease.

Hepatitis A, once called infectious hepatitis, is the most common cause of acute hepatitis. Usually transmitted by food and water contaminated by human waste, such infections can reach epidemic proportions in unsanitary regions. In the United States, increasing numbers of drug abusers are coming down with this form of hepatitis. Both hepatitis B and hepatitis non-A, non-B are spread mainly by blood or blood products, and type B is also known to be transmitted from mother to fetus and by intimate contact, including sexual intercourse. Type B virus is resistant to sterilization of instruments in hospitals, and it is also frequently seen in drug addicts who have shared needles. It often causes an initial episode of liver disease, unlike non-A, non-B, but both forms occasionally lead to chronic hepatitis.

Researchers did not isolate a non-A, non-B virus until 1988. The virus they found, labeled C, probably is the cause of almost all cases of non-A, non-B hepatitis. Another form of hepatitis, called delta hepatitis, is caused by a very small virus that cannot replicate on its own. Instead it requires the presence of the hepatitis B virus. First identified in 1977, the virus has since been characterized as a RETROVIRUS. Delta hepatitis can become chronic.

Acute hepatitis may arise secondary to various infections that involve the liver. It can also occur through ingestion of carbon tetrachloride, the poisonous mushroom Amanita phalloides, arsenic, and certain drugs, including sulfonamides. Mild hepatitis can be cause by two forms of HERPES virus, cytomegalovirus and Epstein-Barr virus. Mild cases of acute hepatitis are treated with bed rest but no drug therapy. In forms involving extensive liver damage, blood-exchange transfusions may be necessary. Chronic hepatitis leads to CIRRHOSIS and liver damage.

Type B virus and certain drugs cause a small percentage of cases, but the cause of most occurrences is unknown; delta virus may be responsible for some of the relapses observed in patients with chronic active hepatitis. Type B infections have also been linked with a form of liver cancer called hepatocellular carcinoma, particularly in Asia and Africa. Of those contracting chronic hepatitis, most are women under the age of 45. Steroids are used to treat certain cases of chronic hepatitis of non viral origin, but their prolonged use in treating hepatitis B is not effective and may even hasten liver damage.

Tests of a newer treatment that combines the use of steroids with alpha interferon, however, are showing promise of greater effectiveness. Alpha interferon is also being tested against hepatitis C. In the 1970's, Baruch S. BLUMBERG developed a diagnostic test for type B hepatitis, and in 1981 a gene-splicing technique was used successfully to determine certain other viral types. A plasma-derived vaccine for type B virus was licensed in 1981, and a vaccine genetically engineered from yeast cells was licensed in 1986. Both are costly. A more recent oral vaccine genetically engineered from animal cells has shown promise in animal tests and may eventually provide a less expensive alternative The hepatitis A and E viruses first enter the gut and begin reproducing.

They spread to the liver and multiply in liver cells. Hepatitis B, C, D, and G enter the bloodstream; when they pass through the liver, they enter liver cells and begin to reproduce. The body attacks the infected cells, which causes the liver to become inflamed. In hepatitis B infection, the liver usually repairs itself, leaving antibodies to the surface antigen, which shows that the infection occurred, but that the body defeated it.

Hepatitis C (HCV) is a form of hepatitis caused by an RNA virus. HCV accounts for the majority of the hepatitis cases previously referred to as non-A, non-B hepatitis. The hepatitis C virus was first identified and described in 1987, and in 1990 a hepatitis C antibody test (anti-HCV) became commercially available to help identify individuals exposed to HCV. In mid-1995 the hepatitis C virus was seen for the first time ever by scientists with the aid of an electron microscope. It is a linear single-strand RNA (ribonucleic acid) virus 40-50 nanometers in size.

It is covered with a lipid envelope and is encased with glycoprotein peplomers or "spikes.".