The occurrence of HBsAg carriership in Leningrad has been found to be 1.4% according to the results of countercurrent immunoelectroosmophoresis (CIEO) and 2.1% according to the results of the passive hemagglutination (PHA) test. In children HBsAg occurs with higher frequency: 1.9% according to the results of CIEO and 3.4% according to the results of the PHA test. The latter test reveals HBsAg carriers more completely, especially in women who have usually less pronounced antigenemia than men. Most of chronic HBsAg carriers are patients with chronic forms of hepatitis B (chronic active hepatitis and chronic persistent hepatitis); frequently they become the source of infection among their relatives under the conditions of family contacts. A complex of antiepidemic measures is necessary in the foci of chronic HBsAg carriership.
The results obtained in the study of the characteristic features of the spread of viral hepatitis B under the conditions of family foci are presented. Children with viral hepatitis B have been found to infect 4-5 persons per 1,000 contacts, while adults infect not more than 1 person per 1,000 contacts. The results of the study have led to the conclusion that the idea of the potential danger of hepatitis B patients as the source of infection depends on the forms of the infectious process taken into account in evaluating its epidemiological significance. Latent cases of hepatitis B virus infection appear more frequently among the contacts of sick children than among those of sick adults, but the manifest forms of the disease are more frequently caused by infection contacted from sick adults.
In regions with a low endemic incidence of hepatitis B familial foci of those with a history of viral hepatitis B and HBsAg carriers are less actual objects of epidemiological surveillance than foci of group diseases, chronic carrier state of HBsAg.
The complete set of specific markers of hepatitis B has been identified, thus making it possible to evaluate the spread of this infection in family foci, as well as the intensity and dynamics of the epidemic process, under the conditions of prolonged observations. The study has shown that the spread of hepatitis B infection is determined by the presence of HBeAg in antigen-positive patients with viral hepatitis B and HBsAg carriers.
Dynamic observation on 126 foci of infection formed by patients with manifest forms of chronic hepatitis B, 41 foci of chronic hepatitis of unknown etiology, and 37 foci formed by chronic "healthy" carriers was made. In the foci of type 1 the epidemic process developed intensively and was manifested mainly by HBsAg carriership in persons having had contacts with the patients. During the period of observation 43.0% of new cases of infection were detected. In the foci of types 2 and 3 the frequency of contacting infection was not different from that in the control group of the population.
The intensity of detection and time course of the main markers of virus infection were studied in subjects who had contacts with patients in 74 foci with chronic active hepatitis, 52 with chronic persisting hepatitis and 41 with chronic hepatitis of unknown etiology. A high (up to 80.7%) frequency of detection of HBsAg, anti-HBs, anti-HBc was established in contact subjects which showed a trend of growth with the increase of the time of their contact with the source of infection.