Hepatitis B Virus Essay

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Hepatitis B Virus

Characteristics:

Hepatitis B Virus (HBV) is a double-stranded DNA virus in the Hepadnaviridae family. The infectious particle is 42nm in diameter, with a genome 3200 nucleotides long. It has an outer envelope and an icosahedral nucleocapsid, which contains viral DNA polymerase and has a diameter of 27nm. The envelope contains the HBV surface antigen (HBsAg); this is the molecule to which anti-HBV antibodies are directed. The non-infectious hepatitis B particles are composed of HBsAg only and come in the form of filaments and spheres. Their only likely purpose is binding up antibodies so the infectious particles can remain free. In humans HBV infects hepatocytes where it replicates within the nucleus
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Most other areas including northern and western Europe, North America, Australia, New Zealand, Mexico and the southern part of South America have low rates of infection (<2%). Chronic HBV carriers can spread the infection. Infection from carriers is low in North America and northern Europe (<0.5%), but is >10% in some areas of the Far East. 5,000 people in the US die from HBV each year and there are currently 1 million chronically infected people in the US. Worldwide 2 billion people have been infected, with 350 million chronically and 1.5 million die each year.

Symptoms:

Symptoms include loss of appetite (anorexia), fever, nausea with vomiting and jaundice. In this case, jaundice is caused when extra subunits of hemoglobin called bilirubin build up in the body due to liver damage. The word hepatitis means inflammation of the liver and with HBV infection the liver is often enlarged and tender. A HBV infection can be acute or chronic. An acute infection can resolve itself spontaneously, with rates as high as 90-95% in adults, but is considered chronic if it lasts more than 6 months. The rates of a HBV infection becoming chronic is 90% in neonates but drops with age to between 5-10% in adults. Some are chronically infected carriers. These people have hepatitis in their liver but they are otherwise normal.

Liver diseases such as cirrhosis and hepatocellular carcinoma are the major…

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