Hepatitis B virus viral load and treatment decision

Hepatitis E: an underestimated emerging threat

Hepatitis E virus (HEV) is the most common cause of viral hepatitis in the world. It is estimated that millions of people are infected every year, resulting in tens of thousands of deaths. However, these estimates do not include industrialized regions and are based on studies which employ assays now known to have inferior sensitivity. As such, this is likely to represent a massive underestimate of the true global burden of disease. In the developing world, HEV causes large outbreaks and presents a significant public-health problem. Until recently HEV was thought to be uncommon in industrialized countries, and of little relevance to clinicians in these settings. We now know that this is incorrect, and that HEV is actually very common in developed regions. HEV has proved difficult to study in vitro, with reliable models only recently becoming available. Our understanding of the lifecycle of HEV is therefore incomplete. Routes of transmission vary by genotype and location: endemic regions experience large waterborne epidemics, while sporadic cases in industrialized regions are zoonotic infections likely spread via the food chain. Both acute and chronic infection has been observed, and a wide range of extrahepatic manifestations have been reported. This includes neurological, haematological and renal conditions. As the complete clinical phenotype of HEV infection is yet to be characterized, a large proportion of cases go unrecognized or misdiagnosed. In many cases HEV infection does not feature in the differential diagnosis due to a lack of knowledge and awareness of the disease amongst clinicians. In combination, these factors have contributed to an underestimation of the threat posed by HEV. Improvements are required in terms of recognition and diagnosis of HEV infection if we are to understand the natural history of the disease, improve management and reduce the burden of disease around the world.

Hepatitis E virus infection

Hepatitis E virus (HEV) infection can lead to acute and chronic hepatitis as well as to extrahepatic manifestations such as neurological and renal disease; it is the most common cause of acute viral hepatitis worldwide. Four genotypes are responsible for most infection in humans, of which HEV genotypes 1 and 2 are obligate human pathogens and HEV genotypes 3 and 4 are mostly zoonotic. Until quite recently, HEV was considered to be mainly responsible for epidemics of acute hepatitis in developing regions owing to contamination of drinking water supplies with human faeces. However, HEV is increasingly being recognized as endemic in some developed regions. In this setting, infections occur through zoonotic transmission or contaminated blood products and can cause chronic hepatitis in immunocompromised individuals. HEV infections can be diagnosed by measuring anti-HEV antibodies, HEV RNA or viral capsid antigen in blood or stool. Although an effective HEV vaccine exists, it is only licensed for use in China. Acute hepatitis E is usually self-limiting and does not require specific treatment. Management of immunocompromised individuals involves lowering the dose of immunosuppressive drugs and/or treatment with the antiviral agent ribavirin.