Hepatitis B virus and hepatitis C virus co-infection: additive players in chronic liver disease?

Hepatitis B virus (HBV) and hepatitis C virus (HCV) share modes of transmission and their combined infection is a fairly frequent occurrence particularly in areas where the two viruses are endemic and among subjects with a high risk of parenteral infections. Moreover, the number of coinfected patients is likely higher than is usually thought. In fact, many studies have shown that HBV genomes may also be present in HBsAg-negative patients, particularly in those with HCV-related chronic hepatitis. This condition is commonly called "occult HBV infection". Much evidence suggests that coinfection by HBV and HCV may have considerable clinical relevance. In particular, this condition is generally believed to be a factor favouring the progression of liver fibrosis toward cirrhosis and the development of liver cancer, and in case of both overt and occult HBV infection. In spite of its potential clinical impact, however, there is few information about the possible interplay between the two viruses. Here, we concisely reviewed the available data on the virological and clinical features of the dual HBV/HCV infection prospecting the aspects that should be highlighted in the nearest future for improving the knowledge on this important field of the hepatology.