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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A cooperative study was undertaken to compare the frequency of hepatitis viral antigens and antibodies among blood donors in the Soviet Union and the United States. Age‐ and sex‐stratified blood donors were identified and their sera tested for hepatitis B surface antigen (HBsAg), antibody to HBsAg (anti‐HBs), antibody to the hepatitis B core antigen (anti‐HBc), and antibody to the hepatitis A virus (anti‐HAV). A total of 994 Soviet blood donor sera from five different regions and 1,178 American donor sera from six different regions were tested in the USA. Among the Soviet donors, 450 (45%) had some marker of exposure to the hepatitis B virus; while among the American donors, 94 (8%) did. Of the Soviet donors 848 (85%) were positive for anti‐HAV, compared with 403 (34%) of the American donors. For 1,977 serum samples that were evaluated in both countries for HBsAg, techniques in the USSR identified 36 HBsAg‐positive samples, while the technique in the USA found 38 HBsAg‐positive samples; however, only 24 were judged to be HBsAg‐positive by assays in both countries. Testing of these same 1,977 sera for anti‐HBs revealed that the radioimmunoassay used in the USA identified many more antibody‐positive donors than the immuno‐autoradiography technique used in the Soviet Union. When a portion of the sera were tested by similar radioimmunoassay techniques in each country, there was comparability of results for anti‐HBs, as well as for anti‐HAV, and anti‐HBc. The results permit calculation of age and sex prevalence of hepatitis B and hepatitis A serologic markers for blood donors within and between each country. They also allow comparison, on the same sera, of test methodologies in use in the Soviet Union and in the United States.

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