Hepatitis E virus infections in Europe.

Hepatitis E virus (HEV) is the most common cause of acute viral hepatitis worldwide. The systematic use of improved tools for diagnosing and genotyping has completely changed our understanding of the epidemiology and clinical consequences of HEV infection. Most cases of HEV in Europe arise from infected animals such as pigs, wild boar, deer and rabbits. Zoonotic HEV genotypes (HEV genotypes 3-8) are mainly food-borne or transmitted by direct contact, but recent data suggest that infection can also be water-borne or even iatrogenic throught contamined blood products. HEV-3 is the most prevalent genotype in Europe but the geographic distributions of the 3 major clades and subgenotypes (HEV-3abjkchi, HEV-3efg, and HEV-3ra) differ. Most HEV-3 infections are asymptomatic but they can result in severe acute hepatitis in patients with chronic liver disease, chronic hepatitis in immunocompromised patients, and to extra-hepatic manifestations. Despite more frequent reports of symptomatic hepatitis E cases across Europe, systems for monitoring HEV infections vary greatly. Severe HEV-associated illnesses, hospitalizations and deaths are probably underestimated. The seroprevalence and incidence of locally acquired hepatitis E varies between and within European countries and over time. The precise origin of these variations is uncertain but may be linked to environmental factors or the degree to which HEV contaminates the human food chain. Collaborative initiatives such as the establishment of the One Health platform for HEV sequences (HEVnet database) will be very useful for a better understanding of the epidemiology of HEV in Europe and the development of effective prevention strategies.