[Epidemiological aspects of Helicobacter pylori infection].

Helicobacter pylori is thought to infect about half the world's population. The prevalence of H. pylori infection varies widely by geographic area, age, ethnicity and socioeconomic status. Rates appear to be higher in developing countries, where most infections occur during childhood. Inadequate sanitation, low socioeconomic status and overcrowding seem to be related to a higher prevalence of H. pylori infection. No predominant route of transmission has been identified, and possibilities include the fecal-oral, oro-oral and gastro-oral routes. Recent studies show that H. pylori strains expressing the biologically active CagA protein are more closely associated with stomach cancer.