Hepatitis C virus (HCV) and hepatitis B virus (HBV) co-infection can be encountered in either virus endemic countries. Co-infection can also be found in populations at risk of parenteral transmission. Previous studies demonstrated a high risk of liver disease progression in patients with HCV/HBV co-infection; thus, they should be treated aggressively. Previous evidence recommended therapy combining peginterferon (pegIFN) alfa and ribavirin for co-infected patients with positive HCV RNA. Recent trials further advise using direct-acting antivirals (DAAs) for the clearance of HCV in the co-infected patients. Reactivation of HBV has been observed in patients post-intervention, with higher risks and earlier onset in those having had HCV cured by DAA- versus pegIFN-based therapy. The mechanism of HBV reactivation is an interesting but unsolved puzzle. Our recent study revealed that in vitro HBV replication was suppressed by HCV co-infection; HBV suppression was attenuated when interferon signaling was blocked. In vivo, the HBV viremia, initially suppressed by the presence of HCV super-infection, rebounded following HCV clearance by DAA treatment and was accompanied by a reduced hepatic interferon response. In summary, major achievements in the treatment of HCV/HBV co-infection have been accomplished over the past 20 years. Future clinical trials should address measures to reduce or prevent HBV reactivation post HCV cure.

Chronic hepatitis B virus (HBV) infection due to perinatal mother-to-infant transmission (MTIT) remains a serious global health problem. Despite passive-active immunoprophylaxis using hepatitis B vaccination with or without hepatitis B immunoglobulin (HBIg), up to 8-10% of newborns still acquire HBV infection. Understanding the mechanisms of MTIT is essential for the interruption of HBV transmission. There are three possible routes of transmission: intrauterine transmission, transmission during delivery (intrapartum) and postnatal transmission through close contact or breast milk (postpartum). Overall, positivity for hepatitis B e antigen (HBeAg) and the high viral load of the mothers are the two most important risk factors related to MTIT of HBV. This article briefly reviews the viral factors related to MTIT of HBV and discusses the issues that warrant further investigation.

Chronic hepatitis B (CHB) exhibits a variety of clinical outcomes, ranging from spontaneous resolution of hepatitis B to severe adverse consequences, including the development of cirrhosis, hepatic failure, and hepatocellular carcinoma. The heterogeneous clinical courses of chronic hepatitis B virus (HBV) infection reflect the complex host-virus interactions, and point to the difficulty and necessity of identifying the patients at risk. With the advance of HBV virology, several viral factors have been found to be associated with the long-term clinical outcomes of CHB patients. Different viral factors probe different aspects of CHB. Integration of these viral factors may help to determine the disease state of patients more accurately, and identify the patients who require timely antiviral therapy to prevent the development of detrimental clinical outcomes. In this article, we will introduce the conventional and emerging viral factors that are associated with clinical outcomes and discuss their utility in a clinical setting.

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