Typical acute hepatitis was reproduced in a human volunteer immune to hepatitis A virus (HAV) after oral administration of pooled stool extracts from presumed cases of epidemic non-A, non-B hepatitis. Markers of hepatitis B infection, anti-HAV IgM, and increase in total anti-HAV level were not detectable in the volunteer’s sera during the course of infection. Spherical 27- to 30-nm virus-like particles were visualized by immune electron microscopy (IEM) in stool samples collected during preclinical and early postclinical phases. These particles banded in CsCl at a buoyant density of 1.35 g/cm³. They reacted in the IEM test with sera from individuals who had experienced two non-B hepatitis episodes but did not react with sera from routine anti-HAV IgM-positive hepatitis patients. Intravenous inoculation of cynomolgus monkeys with the virus-containing stool extract resulted in histopathologically and enzymatically confirmed hepatitis, excretion of virus-like particles, and antibody response to them.

The International Committee on Taxonomy of Viruses (ICTV) has recently approved several proposals submitted by the present Caliciviridae Study Group. These proposals include the division of the family into 4 new genera designated Lagovirus, Vesivirus, "Norwalk-like viruses (NLVs), and "Sapporo-like viruses (SLVs); the latter 2 genera were assigned temporary names until acceptable names can be determined by the scientific community. The genera have been further divided into the following species: Feline calicivirus and Vesicular exanthema of swine virus (genus Vesivirus), Rabbit hemorrhagic disease virus and European brown hare syndrome virus (genus Lagovirus), Norwalk virus (genus NLV), and Sapporo virus (genus SLV). In addition, the ICTV approved a proposal to remove the hepatitis E virus from the Caliciviridae into an "unassigned classification status.

Hepatitis E is an acute, icteric, self-limiting disease, which is spread widely in many tropical and subtropical countries where it occurs both in the form of epidemics of variable magnitude or sporadically. Hepatitis E affects young adults, rather than children, and causes a high mortality rate, particularly in pregnant women. In industrialized countries this disease occurs occasionally as imported sporadic cases. The aetiological cause of hepatitis E is a virus, hepatitis E virus (HEV), which is temporally classified as a member of the Calicivirus family, although its genomic composition is unique. There are experimental data as well as epidemiological observations allowing us to assume that hepatitis E may be a zoonosis as HEV is pathogenic for some domestic and wild animals. Recently, serological assays based on the use of recombinant or synthetic antigens were developed and applied to determine the prevalence of antibody to HEV (anti-HEV) in various epidemic and non-epidemic settings. In suspected hepatitis E cases, anti-HEV seropositivity was detected at an elevated rate but the overall seroprevalence of anti-HEV in normal human populations of endemic areas appeared to be unexpectedly low. A low but constant presence of anti-HEV seropositivity was observed also in non-endemic industrialized countries. In some of these countries, anti-HEV seropositivity was accumulated in groups of patients with various liver and non-liver pathologies and certain groups at risk for blood-borne infections.

Infection with hepatitis E virus was transmitted experimentally to domestic pigs (Sus scrofa domestica).

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