Shellfish as a Potential Source of Hepatitis E Virus: Epidemiological Evidence, Biological Plausibility, and Research Gaps

Hepatitis E virus (HEV) is an important cause of acute and chronic hepatitis worldwide, transmitted primarily through waterborne exposure and zoonotic foodborne pathways. In recent years, shellfish have attracted growing attention as a potential vehicle for HEV transmission. This interest is driven by epidemiological observations linking shellfish consumption to human HEV infection and by repeated detection of HEV RNA in bivalve mollusks across multiple geographic regions. This review critically evaluates the current evidence by integrating epidemiological data, environmental and food surveillance studies, and mechanistic insights into viral accumulation in shellfish. Signals from outbreak investigations, observational studies, seroepidemiological surveys, and case reports suggest that shellfish may contribute to HEV exposure. However, these findings are largely associative, methodologically heterogeneous, and limited by the absence of explicit documentation of raw or undercooked shellfish consumption in many cases. To date, no study has recovered infectious HEV from shellfish, nor has any established molecular epidemiological linkage between shellfish-derived HEV and human infections. Mechanistic knowledge from norovirus and hepatitis A virus demonstrates that bivalves can bioaccumulate enteric viruses through filter feeding, yet HEV-specific processes governing viral binding, persistence, and infectivity within shellfish remain poorly defined. Surveillance data reveal marked geographic variation in HEV RNA detection among shellfish species and production areas. Overall, existing evidence supports shellfish as a biologically plausible but unconfirmed source of HEV exposure. Addressing key knowledge gaps-particularly through direct infectivity assessments and high-resolution molecular linkage studies-will be essential to determine the public health significance of shellfish within the broader ecology of HEV transmission.