Objectives: To assess the rate of intrafamilial transmission of Helicobacter pylori infection in the general population and the role of a family's social background.
Design: Population survey.
Setting: Campogalliano, a town in northern Italy with about 5000 residents.
Participants: 3289 residents, accounting for 416 families.
Main outcome measures: Prevalence of H pylori infection assessed by presence of IgG antibodies to H pylori.
Results: The overall prevalence of H pylori infection was 58%. Children belonging to families with both parents infected had a significantly higher prevalence of H pylori infection (44%) than children from families with only one (30%) or no parents (21%) infected (P<0.001). Multivariate analyses confirmed that children with both parents positive had double the risk of being infected by H pylori than those from families in which both parents were negative. Family social status was independently related to infection in children, with those from blue collar or farming families showing an increased risk of infection compared with children of white collars workers (odds ratio 2.02, 95% confidence interval 1.16 to 3.49).
Conclusions: H pylori infection clusters within families belonging to the same population. Social status may also be a risk factor. This suggests either a person to person transmission or a common source of exposure for H pylori infection.