Hepatitis B

Causative agents

Hepatitis B is a hepadnavirus that is constructed of a circular genome mainly of DNA but may replicate through an RNA intermediate form. Replication of the virus takes place in the liver. HBV has been classified into 8 genotypes and further into subgenotypes.[1]

Statistics

2 billion people are infected worldwide with an estimated 600,000 deaths each year.[2] 90% of infants infected with HBV will become chronic carriers (in contrast with 10% of adults).[2] 25% of these will die from liver cancer or cirrhosis (scarring of the liver tissue).  HBV is predominantly a disease of the developing world, with the highest burden of disease existing in Sub-Saharan Africa, Asia and the Pacific Islands. [3]

Modes of Transmission

HBV is 50 to 100 times more infectious than HIV and, unlike HIV, can survive in the open air for up to 7 days.[3] Any body fluid contains the virus and contact can result in infection, including blood, saliva, semen, vaginal secretions, and to some degree sweat, breast milk, tears and urine.[3]

Methods of diagnosis

Most methods of diagnosis rely on serology, detecting the presence of antigens (core or envelope), IgG, and IgM antibodies, which antibodies target HBV core and surface antigens.  Of these, the most commonly used are tests for the HBV surface antigen (HBsAg) and for antibodies targeting the HBV core antigen (anti-HBc). However, real-time PCR testing is the most advanced method of diagnosis for Hepatitis B virus. It detects the presence of the virus through its DNA before the body creates antibodies and before symptoms are present. It also does not have false positives from lingering antibodies after the virus is gone.

Annotated Bibliography

1. Lazarevic, I., M.Cupic, D.Delic, N.S. Svirtlih, J. Simonovic, and T. Jovanovic, Distribution of HBV genotypes, subgenotypes and HBsAg subtypes among chronically infected patients in Serbia. Archives of Virology. 2007; 152(11):2017-25.

2. Anonymous, Hepatitis B Fact Sheet No. 204. 2008, World Health Organization.

3. Lavanchy, D., Hepatitis B virus epidemiology, disease burden, treatment, and current and emerging prevention and control measures. J Viral Hepat, 2004. 11(2): p. 97-107.