Cohort study of intestinal infection with campylobacter in Mexican children.

A cohort of 179 children under 5 years of age from a low-income urban community was followed up for a year to determine the incidence of symptom-producing and of diarrhoea-free campylobacter intestinal infections, and thus their illness-to-infection ratio. 66% of all children had at least one campylobacter infection, one-third of these being associated with diarrhoea. The annual incidence of all campylobacter infections was 2.1 episodes per child. The incidence was inversely related to age (r = -0.78 p less than 0.02). The illness-to-infection ratio, which in infants younger than 6 months was 1:2, was negatively associated with age (r = -0.7, p less than 0.02). Only symptom-producing infections occurring early in life seemed to protect against subsequent infections.