Chronic infection

The hepatitis B and C viruses (HBV, HCV) are classic examples of viruses that give rise to a long-term infection with high levels of virus replication, known as a chronic infection. Between 5 and 10% of individuals infected with HBV and 80% of those infected with HCV fail to eliminate virus after acute infection, and will continue to harbor the virus within their hepatocytes for months or years.  In chronic infections the very high rate of virus replication means that high levels of HBV and HCV are found in the blood of these indi- viduals. Estimates suggest that over 300 million people worldwide carry HBV or HCV in their blood and body fluids that are continuously shed from the body, making carriers a serious transmission risk. HBV is transmitted in blood and body fluids, but is also passed vertically from mother to offspring. The exact details of HCV transmission, other than in blood and body fluids, are not known. Despite high levels of virus replication, some chronic carriers are asymptomatic but others suffer long-term CPE of infected hepato- cytes that can result in a greatly increased risk of cirrhosis of the liver and hepatocellular carcinoma. At present, in the UK, HCV infection is the predominant condition that leads to the need for liver transplantation.