As many as half of the world's population is infected with H. pylori. Those living in developing countries or crowded, unsanitary conditions are most likely to contract the bacteria, which is passed from person to person. H. pylori only grows in the intestines, and is usually contracted during childhood. Interestingly, many people have this organism in their gastrointestinal tract but don't get an ulcer or gastritis. It seems that other factors must also be present for the damage to take place. The factors that increase your risk for an ulcer from H. pylori include: - Inheritance, through your genes, of certain strains of the bacteria that are more dangerous than others
- Abnormal immune response in your intestines
- Certain lifestyle habits, like coffee drinking, smoking, and ongoing stress
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