We have continued to investigate viral as well as non-viral risk factors for hepatocellular carcinoma (HCC) in both high- and low-risk populations. We provided the first set of definitive epidemiologic data linking dietary aflatoxin exposure to human HCC risk. We also established that hepatitis C plays a negligible role in HCC risk in China, although it role in HCC development in African Blacks, another high-risk population, is quite substantial.

Among Los Angeles blacks and whites, we documented the increasingly important role of chronic hepatitis C infection in HCC development in this low-risk population. We also demonstrated that p53 mutations are uncommon events in oral contraceptive-related HCC in this population.

Two hepatotropic viruses, termed HGV and TTV, were identified and characterized recently. We found no evidence that HGV or TTV contributes to HCC development in South African Blacks. However, among Los Angeles blacks and whites, we observed statistically significant excess risk for HCC among HGV-infected individuals that was independent of the effects of hepatitis B and/or C infections.