Environmental considerations in hepatitis E virus transmission: Is there a missing link?

Hepatitis E virus (HEV) is a zoonotic infection that varies according to genotype and geographical location. The full environmental and public health impact of hepatitis E remains uncertain. In this review, we aim to synthesise the evidence regarding HEV circulation in the environment. A literature search was conducted regarding HEV transmission and findings in environmental context, and this was synthesised to propose a hypothesis and identify gaps in our current understanding. Environmental spillover occurs due to increased interactions at the human-animal-environmental interface, with multiple causative factors. HEV genotypes 3 and 4 have been documented in pigs, deer, chicken, rat, mongoose, rabbit, dolphin, cats, dogs and horses. Other HEV genotypes 1,2 and 5-7 have been found in bandicoot, musk shrew, mink, moose, fish and camel. HEV seropositivity has also been identified in ruminant species without HEV - related sequences being identified. HEV has been found in fruit, shellfish and crops irrigated with infected water. This leads to environmental contamination. HEV circulates in the environment via the asymptomatic wild animal host with episodes of spillover into domestic animal populations with increasing burden within the everchanging 'virosphere'. Through domestic animal amplification, the spillover effect from both wild and domestic animal populations leads to human amplification causing disease with high morbidity and mortality in certain patient populations. Further research is required to consider the viral determinants for HEV cross-species infection and how this relates to HEV-contaminated food products and its impact on environment and human health.