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.

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Different patterns of disease were observed among 11 chimpanzees who were inoculated intravenously with hepatitis E virus (HEV) positive fecal specimens from four different outbreaks (Nepal 1981, Uzbekistan 1981, Pakistan 1985, and Mexico 1986). Five chimpanzees had marginal or no liver enzyme elevations within 70 days of inoculation. Two of the chimpanzees had limited viremia, but did not produce detectable antibody. The four remaining chimpanzees had liver enzyme elevations, viral shedding, viremia, seroconversion to anti-HEV, and detectable HEV antigen in liver biopsy specimens. These results may reflect the range of infection patterns that develop in humans after natural exposure to the HEV.

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