Transmission of Helicobacter pylori among siblings.

Background: Helicobacter pylori infection causes chronic digestive diseases with a major public-health impact, yet the design of prevention measures is hampered by limited knowledge of transmission pathways. We studied the effect of family composition on H. pylori prevalence among rural Colombian children aged 2-9 years.
Methods: 684 children were screened for H. pylori with the 13C-urea breath test. For each child, birth order, birth spacing, number of 2-9-year-old siblings, and number of H-pylori-positive 2-9-year-old siblings was recorded. Odds ratios were estimated by logistic regression, controlling for hygiene-related exposures, socioeconomic indicators, and the number of children in the household.
Findings: The odds of infection increased with the number of 2-9-year-old siblings in the household (odds ratios 1.4, 2.3, 2.6, and 4.3 for one, two, three, and four to five siblings, respectively). Compared with first-born children, odds ratios for children born second and third to ninth were 1.8 (95% CI 1.0-3.3) and 2.2 (1.0-4.3), respectively. Compared with children born 10 or more years after the next older household member, those born within 4 years were 4.1 times (CI 2.0-8.6) more likely to be infected; the age gap to the next younger household member displayed a weaker effect. The number of H-pylori-positive 2-9-year-old siblings had a particularly strong effect gradient (1.5, 3.2, 5.6, and 7.1, for one, two, three, and four positive siblings, respectively).
Interpretation: Among rural Andean children younger than 10 years, H. pylori infection seems to be transmitted most readily among siblings who are close in age, and most frequently from older siblings to younger ones.