A seroepidemiologic study of hepatitis A in Spanish children. Relationship of prevalence to age and socio-environmental factors.

Three child population groups from the Madrid area were studied for anti-HAV antibodies. Analysis was carried out with respect to age and socio-environmental factors. The population understudy was composed of 156 children, with ages ranging from 1 to 14 years; they were stratified in three socio-environmental groups (white-family unit, gypsy-family unit and orphanage), and also divided into subgroups according to age. As a whole, an age-related increase in prevalence was found. The overall seroprevalence by socio-environmental groups was: gypsy-family unit 63%, orphanage 46%, and white-family unit 23%. Significant differences between groups appeared from seven years on, being more marked among the eldest subgroups. Among the factors evaluated, hygienic-sanitary conditions and overcrowding influenced the high prevalence rate found in the gypsy-family unit subjects, whereas overcrowding appeared to be responsible for the higher prevalence in orphanage residents, as compared to white-family unit children.