Survey of delta infection in the Naples basin: a possible epidemiologic model for endemic areas.

The prevalences of delta co-infections and superinfections in 100 randomly selected subjects for each year from 1977 to 1982 and in all the subjects of subsequent years until April 1986, admitted to our Department with acute viral hepatitis B (AVHB), were evaluated and compared with the annual incidence of cases of AVHB reported in Naples during the same period. Moreover, anti-delta antibodies were determined in the sera of 25 consecutive cases of HBsAg-positive chronic active hepatitis and 25 consecutive cases of HBsAg-positive chronic active hepatitis and 25 consecutive cases of HBsAg-positive cirrhosis, respectively, for 1977, 1980, 1983 and 1986. Our data show a high, constant circulation of HDV and a decrease in its incidence in acute forms over the last 3 years, which coincides with the parallel lower incidence of AVHB, but which is not reflected in the delta prevalence in the chronic forms. They also indicate the possible existence of alternate cycles of increase and decrease in the infection, partly dissociated from HBV circulation, which present peculiar epidemiologic characteristics.