This is a very common bacterial infection of the stomach lining. It is thought to be caught in childhood and is very common in developing countries. In about 10% of infected individuals the bacterium may lead to a significant increase in the amount of acid produced by the stomach and this may lead to duodenal ulceration. The majority of people with H. pylori infection will be unaware of the infection or may develop intermittent indigestion (dyspepsia). There is an association between long standing infection with H. pylori and an increase in the risk of developing cancer of the stomach. Patients who see their GP with indigestion (dyspepsia) may be checked (by a blood or breath test) to see if they are infected with H. pylori.