Hepatitis E virus (HEV) infection is one of the main causes of acute hepatitis in both developed and developing countries. This infectious disease has a high prevalence and incidence in Europe. HEV infection has a greater clinical impact in vulnerable populations, such as immunosuppressed patients, pregnant women and patients with underlying liver disease. Therefore, the Study Group for Viral Hepatitis (Grupo de Estudio de Hepatitis Víricas, GEHEP) of the Spanish Society of Infectious Diseases and Clinical Microbiology (Sociedad Española de Enfermedades Infecciosas y Microbiología Clínica, SEIMC) believed it very important to prepare a consensus document to help in decision-making regarding diagnosis, clinical and therapeutic management, and prevention of HEV infection.

Infection with hepatitis E virus (HEV) is a significant cause of morbidity and mortality, representing an important global health problem. Our understanding of HEV has changed completely over the past decade. Previously, HEV was thought to be limited to certain developing countries. We now know that HEV is endemic in most high-income countries and is largely a zoonotic infection. Given the paradigm shift in our understanding of zoonotic HEV and that locally acquired HEV is now the commonest cause of acute viral hepatitis in many European countries, the focus of these Clinical Practice Guidelines will be on HEV genotype 3 (and 4).

The incidence and prevalence of hepatitis E virus (HEV) infection has increased in many developed countries over the last decade, predominantly due to infection with genotype 3 (G3) HEV. Infection with HEV G3 is important in transplant recipients because it can persist in immunosuppressed individuals, leading, if untreated, to the development of chronic hepatitis and significant liver fibrosis. The British Transplantation Society (BTS) has developed Guidelines for \"Hepatitis E and Solid Organ Transplantation\" to inform clinical teams and patients about hepatitis E, to help increase the recognition of persistent hepatitis E infection, and to provide clear guidance on its management. This guideline was published on the BTS website in June 2017 and aims to review the evidence relating to the diagnosis and management of persistent hepatitis E in solid organ transplant recipients and the methods of prevention of HEV infection. In line with previous guidelines published by the BTS, the guideline has used the Grading of Recommendations, Assessment, Development and Evaluations (GRADE) system to rate the strength of evidence and recommendations. This article includes a summary overview of hepatitis E and transplantation with key references, and the statements of recommendation contained within the guideline. It is recommended that the full guideline document is consulted for complete details of the relevant references and evidence base. This may be accessed at https://bts.org.uk/guidelines-standards/.

The family Hepeviridae consists of positive-stranded RNA viruses that infect a wide range of mammalian species, as well as chickens and trout. A subset of these viruses infects humans and can cause a self-limiting acute hepatitis that may become chronic in immunosuppressed individuals. Current published descriptions of the taxonomical divisions within the family Hepeviridae are contradictory in relation to the assignment of species and genotypes. Through analysis of existing sequence information, we propose a taxonomic scheme in which the family is divided into the genera Orthohepevirus (all mammalian and avian hepatitis E virus (HEV) isolates) and Piscihepevirus (cutthroat trout virus). Species within the genus Orthohepevirus are designated Orthohepevirus A (isolates from human, pig, wild boar, deer, mongoose, rabbit and camel), Orthohepevirus B (isolates from chicken), Orthohepevirus C (isolates from rat, greater bandicoot, Asian musk shrew, ferret and mink) and Orthohepevirus D (isolates from bat). Proposals are also made for the designation of genotypes within the human and rat HEVs. This hierarchical system is congruent with hepevirus phylogeny, and the three classification levels (genus, species and genotype) are consistent with, and reflect discontinuities in the ranges of pairwise distances between amino acid sequences. Adoption of this system would include the avoidance of host names in taxonomic identifiers and provide a logical framework for the assignment of novel variants.

High-throughput sequencing of bile and feces from two pigs experimentally infected with human hepatitis E virus (HEV) of genotype 3f revealed the same full-length consensus sequence as in the human sample. Twenty-nine percent of polymorphic sites found in HEV from the human sample were conserved throughout the infection of the heterologous host. The interspecies transmission of HEV quasispecies is the result of a genomic negative-selection pressure on random mutations which can be deleterious to the viral population. HEV intrahost nucleotide diversity was found to be in the lower range of other human RNA viruses but correlated with values found for zoonotic viruses. HEV transmission between humans and pigs does not seem to be modulated by host-specific mutations, suggesting that adaptation is mainly regulated by ecological drivers.

Hepatitis is transmitted by a number of infectious agents. The epidemiological characterization of waterborne or enterically transmitted non-A, non-B hepatitis (ET-NANBH) is unique when compared with other known hepatitides. We have reported on the molecular cloning of a cDNA clone derived from the etiologic agent associated with ET-NANBH, the hepatitis E virus (HEV). The complete sequence of these first molecular clones, isolated from an HEV-infected human after passage in Macaca fascicularis (cynomolgus macaques), illustrates a distant relationship to other known positive-strand RNA viruses of plants and animals. The translated major open reading frame (ORF-1) from these clones indicates that this portion of the genome encodes a polyprotein with consensus sequences found in RNA-dependent RNA polymerase and ATP/GTP binding domains. The latter activity has been associated with putative helicases of positive-strand RNA viruses. These viral-encoded enzymatic activities identify this region and ORF-1 as containing at least two different nonstructural genes involved in HEV replication. Molecular clones obtained from two other geographically distinct HEV isolates demonstrated sequence heterogeneity in this nonstructural gene region. Further study will be required to elucidate the pathogenic significance (if any) of this observed divergence in the nonstructural region.