Risk of Helicobacter pylori transmission from drinking well water is higher than that from infected intrafamilial members in Japan.

To clarify the route of Hp transmission in Japan, the serolgical prevalence of Hp infection and its background in the families was examined. For serological study, IgG antibodies against Hp were measured by ELISA, and histories were obtained from the 41 enrolled families (162 people). Upper gastrointestinal endoscopies were performed on selected family members with symtoms, and Hp strains from these families were isolated and RAPD performed to explore the route of Hp infection. Hp prevalence in the 41 families increased with age, and there is strong relationship between Hp serological prevalence and a history of drinking of well water. Among the people who have a history of drinking well water, Hp prevalence in those at least 10 years old was 85.3%, which is significantly higher than that in those less than 10 years old (25%) and no history of drinking well water (6.3%). There were 5 families with Hp serologically positive members who have drunk well water and Hp DNA was detected from the well water of all 5 wells. RAPD fingerprinting of isolated Hp strains from these family members suggested that the origin of Hp infection was the well water. In conclusion, it is speculated that most Hp transmission in Japan depends on waterborne transmission and the occurrence of its transmission is strongly associated with the duration of the history of drinking well water.