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What is Chronic Hbv Infection and how is it Prevented with the Hepatitis b Vaccine

Introduction: HBV is a common cause of hepatitis especially in third world countries. Hepatitis B infection affects 300 million people and it is one of the most common causes of chronic liver diseases and hepato- cellular carcinoma world-wide. It belongs to a group of viruses called Hepadna viruses. HBV consist of a core containing DNA and DNA polymerase enzyme for virus replication. This core is surrounded by a protein. Excess of this protein travels in blood in form of hepatitis B surface antigen (HBsAg). HBV is transmitted through intravenous route for example by transfusion of infected blood or blood products, contaminated needles used by drug addicts or acupuncturists, sexual intercourse with infected person because virus is present in saliva, semen and vaginal secretions, and from infected mother to child at the time of delivery. Humans are the only source of infection. It can cause acute and chronic hepatitis

Chronic HBV infection: It is defined as the infection of liver with HBV lasting 6 months or longer. 90% newborns that get infected at birth while 10% immuno-competent young adults develop chronic hepatitis after infection

Types: There are two types of chronic hepatitis depending on with or without active viral replication. After infection with HBV, several antigens (HBsAg, HBeAg, HBcAg) and antibodies (anti-HBsAg, anti-HBeAg, anti-HBcAg) are produced in the blood as a result of immune response of the body. If the body develops all these antibodies with negative HBeAg, then there will be low viral replication. But if the body fails to develop anti-HBeAg with positive HBeAg, then there will be active viral replication.

Symptoms: Many patients with chronic hepatitis are asymptomatic and they are diagnosed either while screening or when complications develop. Uncommon symptoms are fatigue or intermittent jaundice. Complications of chronic hepatitis such as cirrhosis of liver and hepato-cellular carcinoma develop decades after the infection.

Diagnosis: Diagnosis of chronic hepatitis depends upon serology and viral load. Serological tests include detection of viral markers such as HBsAg and HB eAg. Viral load can be determined by polymerase chain reaction and detects HBV DNA. Other important test includes serum transaminases and prothrombin time.

Treatment: Treatment of chronic hepatitis includes alpha interpheron or lamivudine. Selection of treatment depends upon viral replication and condition of patient.

Vaccine against HBV: A recombinant hepatitis B vaccine containing HBsAg is available for prevention of chronic hepatitis. It is capable of producing active immunisation in 95% of normal individuals. However it should be noted that this vaccine is ineffective for those who are already infected. Infection can also be prevented or minimized by intramuscular injections of serum globulins prepared from blood containing anti-HBs. This should be given within 24 hrs, or at most a week, of exposure.