[Non-A, Non-B hepatitis : status of current knowledge (authors' transl)].

The many studies carried out following post-transfusion hepatitis cases, not due to the A and B viruses identified to date, have provided incontestable evidence that cases with all the clinical, biochemical and histopathological characteristics of A and B hepatitis, but etiologically distinct, do exist. These have been temporarily termed "Non-A, Non-B" (NANB). The epidemiology, duration of incubation period and type of evolution, including the risk to evolve towards chronic hepatitis are common to both B and NANB hepatitis. NANB hepatitis can be experimentally transmitted to chimpanzees, but the disease may have milder characteristics. Immunological studies have revealed the presence of corresponding antigens and antibodies in certain NANB hepatitis cases, which may hopefully lead to the development of serological methods of diagnosis after confirmation of these results. Two categories candidate virus have been so far proposed: either DNA viruses similar, to, but immunologically distinct from the hepatitis B virus, or small RNA viruses. The identification and role of such viruses in the determination of NANB hepatitis warrant further study. However, it already appears possible to postulate, on the basis of epidemiological, clinical, immunological and experimental data, that at least two etiologically different types of NANB hepatitis should exist.