Causative agents

Hepatitis B virus (HBV) is one of the smallest enveloped double-stranded DNA virus that is part of the Hepadnaviridae family.  The replication process of HBV that takes place in liver is unique among animal DNA viruses where herein, reverse transcription is involved. It destroys the liver and causes diseases such as cirrhosis and hepatocellular carcinoma. There are 8 distinctly classified genotypes of hepatitis B virus and further recognized subgenotypes. [1], [2]

Epidemiology

Hepatitis B virus (HBV) infection is a worldwide health problem with the highest burden of disease in Asia, Pacific Islands and Sub-Saharan Africa. There are 2 billion people infected worldwide (one third of world’s population), and 400 million suffering from chronic HBV infection (90% of infants and up to 50% of young children infected with hepatitis B will develop chronic infections). HBV infections result in roughly 1 million deaths per year caused by HBV and its complications (HBV-related liver diseases). [3], [4]

Modes of Transmission

Transmission of hepatitis B virus follows the same modes as HIV, but unlike HIV, HBV is 50-100 times more infectious and survive in the open air for at least 7 days. Common modes of transmission are: perinatal (from mothers to infants primarily at birth), early childhood infections (inapparent infection through close interpersonal contact with infected household contacts), unsafe injections practices, blood transfusions and sexual contact. [4]

Diagnosis

Diagnosis of HBV infections is mainly dependent on serological testing, detecting the presence of antigens (core and surface) and antibodies developed against antigens. However serological tests tend to give false negative results in the early period of the infection (before the body creates antibodies and before symptoms are present) and false positives from lingering antibodies after the virus are gone. They provide no reliable measure of viral replication that has been used in monitoring the response of infection to treatment. Detection of HBV DNA by real time PCR testing is the most useful and reliable method. It overcomes the disadvantages of serological tests mentioned above and provides even quantitative data of viral replication which allows monitoring the response to treatment. [5], [6]

Annotated Bibliography

1. 1-K. E. Nelson, C. Williams, and N. Graham., Infectious Disease Epidemiology: Theory and Practice, July 15, 2000 , p :907-921
2. 2-Barbara Rehermann and Michelina Nascimbeni, Immunology of Hepatitis B virus and Hepatitis C virus Infection, NATURE REVIEWS , Volume 5, March 2005, p: 215-229
3. 3-Anonymous, Hepatitis B Fact Sheet No. 204. 2008, World Health Organization.
4. 4-Jinlin Hou, Zhihua Liu, and Fan Gu, Epidemiology and Prevention of Hepatitis B Virus Infection, Int. J. Med. Sci. 2005 2(1),p: 50-57
5. 5-Norman Gitlin, Hepatitis B: diagnosis, prevention, and treatment, Clinical Chemistry. 1997; 43:1500-1506.
6. 6-Erwin Sablon and Fred Shapiro, Advances in Molecular Diagnosis of HBV Infection and Drug Resistance , Int. J. Med. Sci. 2005 2(1), p: 8-16