Epidemiology and natural history of HCV infection.

Worldwide, an estimated 130-170 million people have HCV infection. HCV prevalence is highest in Egypt at >10% of the general population and China has the most people with HCV (29.8 million). Differences in past HCV incidence and current HCV prevalence, together with the generally protracted nature of HCV disease progression, has led to considerable diversity in the burden of advanced liver disease in different countries. Countries with a high incidence of HCV or peak incidence in the recent past will have further escalations in HCV-related cirrhosis and hepatocellular carcinoma (HCC) over the next two decades. Acute HCV infection is difficult to detect because of the generally asymptomatic nature of the disease and the marginalization of at-risk populations. Around 25% of patients with acute HCV infection undergo spontaneous clearance, with increased rates among those with favourable IL28B genotypes, acute symptoms and in women. The remaining 75% of patients progress to chronic HCV infection and are subsequently at risk of progression to hepatic fibrosis, cirrhosis and HCC. Chronic hepatitis C generally progresses slowly in the initial two decades, but can be accelerated during this time as a result of advancing age and co-factors such as heavy alcohol intake and HIV co-infection.