Hepatitis B virus causes hepatitis B. HBV is transmitted by three main modes are via blood,during sexual intercourse and perinatally from mother to newborn. After entering the blood,the virus infects hepatocytes and viral antigens are displayed on the surface of the cells.Cytotoxic T cells mediate an immune attack against the viral antigens on infected hepatocytes is mediated by cytotoxic T cell.Antigen antibody complexes causes some of the early symptoms.e.g. arthralgia,arthritis,urticaria and some complications in chronic hepatitis.

About 5% of patient with HBV infection become chronic carriers.A chronic carrier is someone who has HBsAg persisting in their blood for at least 6 months.The chronic carrier state is attributed to a persistent infection of the hepatocytes,which results in the prolonged presence of HBV and HBsAg in the blood.

A high rate of hepatocellular carcinoma occurs in chronic carriers. Clinical finding: Many HBV infections are asymptomatic and are only detected by the presence of antibody to HBsAg.The incubation period for hepatitis B is 10 to 12 weeks.It causes fever,anorexia,nausea,vomiting and jaundice are typical.Dark urine,pale feces and elevated transaminase levels are seen.

The most laboratory test for the detection of early HBV infection is the immunoassay for HBsAg.Its prolonged presence (at least 6 months) indicates the carrier state and the risk of chronic hepatitis and hepatic carcinoma. Treatment and prevention: Alpha interferon is clinically usefull for the treatment of chronic hepatitis B infections.

Lamivudin,Adenavir are the drugs that reduce hepatic inflammation and lower the levels of HBV in patientsv with chronic active hepatitis. Prevention involves the use if either the vaccine(Recombivax) or hyperimmune globulin(HBIG) or both. Precise recommendations for use of the vaccine and HBIG.All blood for transfusion should be screened HBsAg.No one with a history of hepatitis should donate blood because non-B viruses may be present.