Virus

The hepadnaviruses cause several diseases, including hepatitis B. Hepatitis B is a chronic, debilitating disease of the liver and immune system. The disease is much more serious than hepatitis A for several reasons: it is chronic and long-lasting; it can cause cirrhosis and cancer of the liver; and many people who contract the disease become carriers of the virus, able to transmit the virus through body fluids such as blood, semen, and vaginal secretions.

The hepatitis B virus (HBV) infects liver cells and has one of the smallest viral genomes. A double-stranded DNA virus, HBV is able to integrate its genome into the host cell's genome. When this integration occurs, the viral genome is replicated each time the cell divides. Individuals who have integrated HBV into their cells become carriers of the disease. Recently, a vaccine against Figure 2. First, the virus docks with the host cell. The genetic material of the virus then enters the host cell and the virus loses its capsid. Once inside the host cell, the viral RNA or DNA takes over the cellular machinery to make more viruses. Viral subunits are produced, which are then assembled to make whole viruses. Finally, the new viruses leave the host cell, either by exocytosis or by destroying the host cell. Illustration by Hans & Cassidy. Courtesy of Gale Group.

HBV was developed. The vaccine is especially recommended for health care workers who through exposure to patient's body fluids are at high risk for infection.