Intrafamilial hepatitis A outbreak: projection on the community in an area of Tuscany.

In 1988, 3 intrafamilial cases of hepatitis A occurred in a little town in the nearby of Siena: shellfishes were probably responsible for the index case, close contacts for the two secondary cases, characterized by a very long incubation period (above 60 days). An inapparent infection was detected in one household contact. No other cases of hepatitis A have been observed in that area since the intrafamilial outbreak until now. A seroepidemiological survey was carried out in a group of persons living in the same area, and attending the same school or class-room of one of the secondary intrafamilial cases. 210 sera belonging to 105 teenagers were available; an IgG anti A test was performed on a double serum sample (before and after the outbreak): no seroconversion was observed. Our report underlines the hypoendemicity of hepatitis A infection in our country.