Genetic insights into hepatitis E virus through environmental surveillance in Europe.

Zoonotic hepatitis E has been a growing public health concern in Europe, but the transmission of its causative agent, hepatitis E virus (HEV), remains incompletely understood. Environmental surveillance, particularly through wastewater monitoring, has proven valuable for tracking viral circulation and variant shift during the COVID-19 pandemic, yet its application to HEV is still limited. In this review, we systematically analyzed HEV sequences across Europe, focusing on environmental sources from a genetic perspective. Of more than 13,100 HEV sequences deposited in the NCBI database, only 2.4 % (316/13,118) originated from environmental samples, including wastewater, surface water, and biosolids. Additional typing data from the literature revealed highly uneven geographic distribution, with 97 % of environmental sequences reported from Italy, France, the United Kingdom (UK), Spain, Sweden, and Germany. HEV-3 was the dominant genotype, while HEV-1 and HEV-4 were occasionally detected. Subtypes 3c and 3f were most common, but their prevalence varied across countries and sample types. Some countries, such as France, Sweden, and the UK, exhibited divergent subtype patterns between humans, animals, and environmental sources, whereas others, such as Spain and Germany, showed more consistent distributions. These findings highlight the importance of integrating clinical, veterinary, and environmental surveillance to better understand HEV transmission in Europe under a One Health framework. However, the scarcity of environmental data, technical challenges in sequencing, and lack of standardized protocols limit comprehensive assessment of HEV circulation. Expanding sequencing efforts, improving detection methods, and coordinating international surveillance frameworks will be critical to strengthen HEV monitoring and preparedness against emerging HEV threats.