The type of hepatitis is named for the virus that causes it for example, hepatitis a. Others may have loss of appetite nausea and vomiting diarrhea dark colored urine and pale bowel movements stomach pain jaundice. Yellowing of skin and eyes some forms of hepatitis are mild, and others can be serious. Department of virology, national centre of microbiology, instituto de salud carlos i, road majadahonda pozuelo, km2, majadahonda, 28220 madrid, spain received 7 november 2013 accepted 25 december 2013 published 10 february 2014 academic editors: s. bofill mas, m. ciccozzi, m. This is an open access article distributed under the creative commons attribution license. Which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

Human hepatitis e virus hhev spreads early in life among the population in areas endemic for genotype 1 and infects mainly adults in areas endemic for genotype 3, where it would be responsible for about 10 x25 of cases of suspected acute viral hepatitis of unknown etiology and for a number of subclinical, unrecognized infections. The overall prevalence of antibody to hhev is high in most of the former areas and low in most of the later ones, but wide regional differences have been recorded in both cases. X201c hot spots x201d of hhev infection would exist for both types of strains in particular regions or among particular populations of the world. Studies on pork derivatives, shellfish bivalves, and vegetables for hhev contamination at the sale point need to be extended for evaluating the impact of the agent on food safety, and the meaning of the finding of hhev genotype 1 genomes in urban sewage from developed countries should be established through active surveillance.

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Consensus about technical issues in regard to anti hev testing would improve the knowledge of the hhev epidemiology. Studies in particular regions and populations, and introduction of molecular diagnosis in the clinical setting as a routine tool, would also be required. Introduction one of the mysterious aspects of hepatitis e virus hev is the high seroprevalence of antibody to hev anti hev igg in developed countries where the infection is not endemic, despite the seldom reported cases of acute clinical hepatitis caused by hev in these countries.

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This sentence opened, five years ago, a review article on the hepatitis e virus hev seroprevalence in developed countries, a matter of mystery for the authors of the review 1 . Though the infection by zoonotic hev strains is actually endemic in these regions, there are still reasons, five years later, to share with them some perception of mystery from analyzing the data available about the prevalence of antibody to hev anti hev in the different populations of the world. Such reasons arise both from conceptual and technical issues and from the data and set both light and darkness on the epidemiology of hev. Next pages will try to show the enlighten areas and to suggest ways for illuminating the dark ones. Taxonomic status and general proprieties of human hev the family hepeviridae includes at present five separate groups of viruses of vertebrates.

Viruses from ferrets and rats cluster separately from human related viruses in phylogenetic trees. Finally, strains isolated from trout draw a group independent from the remainder 3 . In a recent review of the information available, a future classification of the family into two genera was proposed on the basis of these genetic relationships, with the avian and mammal viruses drawing a single genus and the viruses from fish a second one 4 . The former genus would consist of four separate species: avian hev, bat hev, hev from rodent and ferret, and human related hev hhev. This last species would be further subdivided into six genotypes, two of them found among wild boars only.

Therefore, all hev strains found among humans would belong to a single viral species consisting of four separate genotypes. Some of these genotypes are exclusive of the human beings and some are shared with other mammal species, as explained below. The hhev virion is a spherical shaped particle about 30 x2009 nm in diameter whose structure resembles the structure of the calicivirus particle under the electron microscope. The viral core protein is the single structural protein of the virion but arranges in different ways to generate a series of structural units. The genome consists of a single linear species of single stranded, 3 x2032 capped rna of positive polarity and of 7.3 kilobases kb in length which is organized in three open reading frames orfs 11 . Orf1 extends for 5.1 x2009 kb and encodes at least four functional, nonstructural proteins displaying activities of methyl transferase, protease, helicase, and rna dependent rna polymerase.