THE EPIDEMIOLOGY AND TRANSMISSION OF HELICOBACTER-PYLORI INFECTION IN CHILDREN

How and when Helicobacter pylori infection is acquired is unknown. Faecal-oral and oral-oral transmission have been demonstrated in animal studies of other Helicobacter species, whilst sero-epidemiological studies in adults show a cohort effect suggesting that primary acquisition occurs in childhood, H. pylori can be detected non-invasively using serology or the C-13-urea breath test, and although the accuracy of both methods is well established in adults, further validation studies are needed in children, especially those under 5 years old, In children, the age-specific prevalences of H. pylori, which are low in developed countries and high in developing countries, suggest that in most cases infection is acquired early in life. Prospective studies show that the incidence of H. pylori infection in adults is about 0.4% per year; in children, studies using the C-13-urea breath test demonstrate incidences in developing and developed countries of 36% and 2.7% per year, respectively. Intra-familial clustering of H. pylori and high prevalences in orphanages and institutions for the mentally retarded suggest that person-to-person transmission of H. pylori is important. In addition, H. pylori infection has been associated with poor childhood socio-economic conditions-with overcrowding and close person-to-person contact through bed sharing being the most consistent and significant associations. However, these studies are liable to recall-bias, Since it is still unclear whether H. pylori is transmitted by the faecal-oral or oral-oral routes, it is possible that both routes exist. To determine how and when H. pylori infection is primarily acquired, further large-scale prospective population-based studies are needed using improved non-invasive tests with the molecular typing of infecting strains.