While zoonotic transmission of hepatitis E virus (HEV) genotypes 3 and 4 is well documented in industrialized countries, emerging hepeviruses and non-zoonotic genotypes present ongoing challenges for surveillance, diagnostics, and public health globally. Following his presentation at ESCMID Global 2026 in Munich, we spoke with Hao Wang, Postdoctor in Infectious Disease, about the role of a One Health approach in strengthening surveillance and diagnostic strategies.
Your talk focused on HEV from a One Health perspective. How does this approach change the way we understand HEV epidemiology in Europe?
In the past, the focus was mainly on clinical cases in hospitals, but these represent only a small part of the overall picture. For example, in Sweden, around 20 to 50 clinical cases are reported each year, yet HEV antibody prevalence among blood donors is about 17 percent. In addition, recent environmental monitoring has found high levels of HEV in wastewater. Together, these findings suggest that HEV is under-recognized, not only in Sweden but across Europe.
A One Health approach helps address this gap by linking animal reservoirs, environmental sources such as wastewater, and human health. This broader perspective improves understanding of how HEV spreads and highlights that hepatitis E is not just a clinical issue, but a wider challenge involving agriculture, food safety, and environmental management.
What are the main animal reservoirs of HEV in Europe, and how well are these characterized?
In Europe, the main reservoirs of HEV genotype 3 are domestic pigs and wild boars. Infection is common in pig populations, and the virus continues to circulate within herds on farms. Genetic studies have shown that strains found in pigs, wild boars, and humans are closely related, supporting their role in transmission.
HEV has also been detected in other animals, including deer, moose, rabbits, rodents, and pets. However, their role as true reservoirs is less well understood.
To what extent is HEV transmission in Europe driven by foodborne exposure versus direct animal contact?
In Europe, HEV is mainly transmitted through food, particularly by consuming raw or undercooked pork, wild boar meat, or related products. Direct contact with animals can also pose a risk, especially for people with occupational exposure such as farmers or slaughterhouse workers, although this affects a smaller group.
With increasingly global food supply chains, this is no longer just a local issue. For example, some HEV-3 subtypes identified in Sweden are likely linked to imported meat products.
How significant is environmental transmission in the European context?
Many studies have found HEV in environmental water sources such as rivers and lakes. However, detection does not necessarily mean transmission. In most cases, the virus is present at very low levels, so the direct risk of infection from water is considered low.
That said, environmental water can still play an indirect role. Contaminated irrigation water may affect vegetables and berries, and heavy rainfall can carry animal waste into coastal areas, where shellfish can accumulate the virus. For this reason, environmental monitoring is important for identifying potential risks before they enter the food supply.
What role does viral genotype diversity play in transmission patterns and clinical risk?
Different HEV genotypes are linked to distinct transmission routes and clinical risks. For example, genotype 1 is mainly spread through contaminated water and is associated with severe outcomes in pregnant women, particularly in low-resource settings. In contrast, genotype 3 is primarily transmitted through foodborne, zoonotic routes and is the most common cause of chronic infection in immunocompromised patients.
There may also be differences within genotypes. Some studies in Europe suggest that certain subtype 3 strains, such as 3c, are associated with milder disease and lower hospitalization rates. However, this remains an area of ongoing research and requires further confirmation.
How well aligned are human, veterinary, and environmental surveillance systems for HEV across Europe?
Surveillance systems for human, animal, and environmental health in Europe are not yet well aligned and often operate separately. Human surveillance is relatively well established, and animal monitoring is carried out in many regions, but environmental surveillance remains limited and is mostly confined to research projects.
For example, analysis of HEV sequences in the NCBI database shows that around 70 percent come from human samples and 27 percent from animals, while less than 3 percent are from environmental sources. To better understand and manage hepatitis E, there is a need for stronger collaboration and shared data platforms across these sectors.
What are the main gaps in surveillance that limit our understanding of HEV transmission?
To better apply a One Health approach to HEV in Europe, several gaps need to be addressed. First, we need to increase environmental surveillance. As seen during COVID-19, wastewater monitoring can provide valuable insights into how viruses spread within communities.
Second, more research is needed on less well-defined animal reservoirs. Although HEV has been identified in a wider range of species, their role in transmission is not fully understood.
Finally, there is a lack of standardized methods for sampling and surveillance in animals and the environment. Without consistent protocols, it is difficult to compare data across studies. Developing shared standards will be important for integrating data across sectors and improving overall surveillance.
What interventions could most effectively reduce HEV transmission?
Improving food safety remains the most effective and practical measure, particularly ensuring that pork and wild boar products are thoroughly cooked. This is especially important for high-risk groups, such as immunocompromised individuals.
Additional steps include strengthening biosecurity on pig farms to reduce virus circulation at the source. Integrating HEV into environmental monitoring – alongside other enteric viruses – could also help provide an early warning system for public health.
Looking ahead, how might climate change or shifts in agricultural practices influence HEV reservoirs and spread in Europe?
Climate change is likely to influence the spread of HEV in Europe, although direct evidence is still limited. A comparable example is tick-borne encephalitis virus (TBEV), where rising temperatures have allowed ticks to expand into new regions, increasing infection rates. Similar environmental changes could affect HEV reservoirs. For instance, milder winters may support larger wild boar populations, potentially increasing virus circulation.
Changes in agriculture may also contribute. Intensified farming, if not matched by effective monitoring and waste management, could increase environmental contamination through manure and wastewater. This may also support transmission through intermediate hosts such as rodents, although their role is still being studied.
Newsletters
Receive the latest pathologist news, personalities, education, and career development – weekly to your inbox.
