[Retrospective (1970-1984) serological study of delta antigen and antibody. Observations on seroconversion and absence of delta in non-A, non-B hepatitis].

335 serum samples collected between 1970 and 1984 from 278 HBsAg positive patients were tested for HDV antigen and HDV antibody (HDV = hepatitis D virus; also referred to as delta virus). The first positive sample was obtained in February 1974. The prevalence of the delta coinfection fluctuated in the following years between 0 and 52% of HBV-infected subjects. It was 40% on average in subjects at risk for HBV infection (i.v. drug abusers, homosexuals and institutionalized mentally retarded subjects) and 6% in persons without risk factors. The antibody was also found in 22% of subjects in a group of drug abusers who recovered from HBV infection (positive for anti-HBs antibody). The study showed that dissemination of HDV infection in Switzerland after 1974 was small clusters occurring mainly in drug users. It also showed that the infection was principally associated with chronic active hepatitis. In addition, sequential serum samples were taken from five patients with chronic hepatitis B superinfected by HDV, over periods of 2 to 13 months. Seroconversion (HDV antigen to HDV antibody) was observed in 4 of these 5 patients, with simultaneous presence of antigen and antibody for periods of 2 to 6 weeks. 167 samples from patients with non-A, non-B hepatitis were all negative for anti-delta antibody.