Epidemiological features of Helicobacter pylori infection in developing countries.

Helicobacter pylori infection has a worldwide distribution, and it has distinct epidemiological features in developing countries. In contrast to that in developed countries, H. pylori infection in developing countries seems to be nearly universal, beginning in early childhood. Children become infected in the first few months of life; in some communities as many as 50% of the children are infected by the age of 5 years, and up to 90% are infected by the time they reach adulthood. In some developing countries with improvements in industrialization, socioeconomic conditions, and hygiene, infection rates are lower. The incidence of H. pylori infection, determined indirectly, also suggests a rate several times higher than that in developed countries. Marked differences in H. pylori seroprevalence have been observed between various ethnic and racial groups. Although the mode of transmission of H. pylori remains uncertain, evidence suggests person-to-person transmission occurs.