[Factors of contagiousness in the epidemiology of hepatitis type B (author's transl)].

Since morbidity of viral hepatitis B is increasing, the causes of diffusion of this infection have been studied. There are several routes of transmission and undoubtedly apparent non-parenteral routes have a great importance. In a study performed on 32 families of HBsAg carriers, familial aggregation of infection has been acquired through close personal contact. Transmission of infection from mother to infant may occur transplacentally for vertical transmission, or, after the birth, for horizontal transmission, so that a high percentage of children is infected. Percutaneous transmission of hepatitis B in families affected by scabies is evident. The presence of infectivity markers is of major importance for transmission of virus: these are HBeAg and specific DNA-polymerase activity of serum. Well, when the carrier exhibits the markers, the contacts are involved in the infection in a high percentage. From this point of view the carriers with chronic liver disease are more dangerous than the asymptomatic ones. The problem of carrier exists: nevertheless it is possible to carry out a better prophylaxis, if we take into account the presence of the infectivity markers.