Hepatitis E: state of the art

Hepatitis E (HEV) has traditionally been thought to be a disease of developing countries. In this setting, HEV causes hepatitis in young adults. It is generally a self-limiting illness, with a good prognosis, except in pregnant women and patients with pre-existing chronic liver disease, in whom the mortality is 20% and 70% respectively.

Traditionally HEV was considered rare in developed countries, and confined to travellers returning from endemic areas. However, recent data has shown that locally acquired HEV infection is common in developed countries. Acute HEV infection in this setting is caused by HEV genotype 3 and appears to have a predilection for middle aged/elderly males. It has a significant morbidity (15%) and carries an adverse prognosis in chronic liver disease. HEV infection is commonly misdiagnosed as drug-induced liver injury. The source and route of infection are currently uncertain, but evidence suggests that HEV genotype 3 is a porcine zoonosis, which can be transmitted via the human food chain.

Until very recently chronic HEV infection was thought not to occur. However studies from Europe have shown that HEV genotype 3 can cause chronic infection with rapidly progressive cirrhosis in patients with immunocompromise. This includes patients taking immunosuppressive therapy following solid organ transplantation and patients with HIV-1 infection (NEJM 2009; 361(10): 1025-7).

HEV IgG seroprevalence in developed countries is variable, with rates of 16% reported from the UK and SW France. These data indicate that HEV infection is either commonly subclinical, or commonly overlooked as a diagnostic possibility. However, the burden of HEV disease in both the developing and developed world is currently uncertain. The worldwide burden of chronic HEV infection may prove to be more considerable than previously thought likely, as countries where HEV is endemic also have a high seroprevalence of HIV.