[Non A-non B hepatitis].

The advances in the study of viral hepatitis etiology have led to differentiate certain cases which are not provoked by already know viruses. That is why these cases are called "non A-non B" Hepatitis. The morphological characteristics of this/these agents, has/have not yet been explained. The most frequent way of transmission is parenteral, and the majority of the cases are known as postransfusional hepatitis. Other ways of transmission are also mentioned. Incubation period is of approximately 2 to 15 weeks; therefore, it is an intermediate period between A and B Hepatitis. Clinical symptoms are milder compared to those presented by B type hepatitis, but they show a lower serologic response. Studies performed up to this date, seem to demonstrate that this type of hepatitis has a tendency to become chronic. Active immunization has not yielded good results; but, passive immunization with immunoglobulin has been effective. It is imperative to develop new specific laboratory techniques in order to identify the responsible etiologic agent or agents.