**2.3.1 Viral hepatitis**

Viral hepatitis, in particular chronic hepatitis B and C, account for over 80% of the cases of primary hepatic cancer. The degree of connection of these two viruses to hepatocellular carcinoma varies depending on the region being evaluated. Most of the hepatitis B-related hepatoma cases are seen in Africa and Asia, whereas most of the hepatitis C-related cases are seen in Europe, the United States and Japan (Bosch et al., 2004). Donato et al. and Shi et al. showed in their respective meta-analysis that chronic hepatitis B and C infection carry a significant risk for hepatoma. This risk was higher in co-infected patients with an odds ratio of 165 and 35.7 in their respective studies (Donato, 1998; Shi, 2005). Individuals with hepatitis B e antigen positivity have also shown to have an increased risk for primary liver cancer with a relative risk of 60.2 compared to a relative risk of 9.6 in those that are hepatitis B e antigen negative (Yang, 2002). Similar observations apply to those who have high hepatitis B DNA levels. In recent times, the improved antiviral therapies against hepatitis B, and the successful vaccination programs have helped lower the incidence of hepatocellular carcinoma particularly in what are considered endemic areas for hepatitis B (Chang et al., 1997; Sung, 2008).

The incidence of hepatitis C-related hepatocellular carcinoma has not seen the same encouraging trend that is been observed in hepatitis B-related cases. This is probably due to the interplay of numerous factors that include the natural history of the hepatitis C virus infection, host responses, age at the time of infection, co-morbidities, and alcohol consumption, to name a few. Approximately 15 to 20% of the chronic hepatitis C-infected individuals will develop cirrhosis over a period of 25 to 30 years from the time of infection (Thein, 2008). In developed countries such as the United States, the majority of the infections occurred from the late 1960s to the 1980s, thus in part explaining the rising number of persons that are being diagnosed with hepatitis C-related cirrhosis over the last couple of decades (Davis, 2010). Hepatocellular carcinoma develops in this population at a rate of 1 to 4% per year, a worrisome statistic considering the escalating numbers of persons diagnosed with hepatitis C-related cirrhosis.
