[Observations on the diffusion of hepatitis A and B virus during an epidemic in a Sicilian town with a high rate of infection].

Epidemiological investigations were carried out during a viral hepatitis outbreak occurring in a Sicilian town of 30,000 inhabitants with poor sanitary standards, with the aim to study the mode of spread of HAV and HBV in conditions of high incidence of infections. HBsAg, anti HBs, anti HAV (RIA), HBeAg, anti HBe and anti HBc were investigated in serum samples from patients, their family contacts and from healthy individuals of different age groups. Morbidity was inferred from case notifications; search of unreported cases among school children, through the study of absenteeism, did not reveal further cases. In all 148 cases, occurred from August 1976 through July 1977 with a peak in January, 44% were under 5 and 93% under 10 years of age. All but 8 of 59 cases in which laboratory data were available were due to HAV. Anti HAV antibodies were highly prevalent in serum samples obtained in February through April 1977: 62% were positive in the 1 to 3 years age group, and more than 90% among school children. Prevalence of HBsAg was age and sex dependent, ranging from 4% to 15%; anti HBs was present in 8% of the children 1-10 years and in 30% or more in age groups 30-41 and over. It is suggested that direct contact between very young children was the main mode of spread of HAV, and inapparent cases the main source of infection, although ambient diffusion through water contamination could not ruled out. HBV was probably propagated mostly by intrafamilial spread with little overt pathology.