Natural history of hepatitis B and C virus infections.

Thirty-five years have already elapsed since the discovery of hepatitis B virus (HBV), and 10 years since that of hepatitis C virus (HCV). Nonetheless, the natural history of HBV and HCV infections has not been fully defined, partly because they do not have subjective symptoms in most cases. Even when liver disease is induced by these hepatitis viruses, the clinical course is slow and mostly insidious. HBV and HCV are much alike in that they both cause a spectrum of clinical conditions ranging from the symptom-free carrier state through chronic hepatitis and liver cirrhosis to eventual hepatocellular carcinoma. Despite a close similarity, infections with HBV and HCV are very different in many aspects, from the early to end stage. Large-scale unbiased studies to sort out the natural history of HBV and HCV infections are lacking, however. Understandably, in view of the fact that only a few decades have passed since these hepatitis viruses were discovered. My personal account on the natural history of HBV and HCV infections is given here, which is based on my experience of over 40 years as a clinical and research hepatologist in Japan, although I am aware that it invites more questions than it answers.