It is estimated half of the world's population is infected by the stomach bacterium Helicobacter pylori.H. pylori has been known as a Class 1 Cancerogen since 1994 (World Health Organisation). People have a 6-7 times higher risk for stomach carcinoma if H. pylori positive. No symptoms are normally present during the first years of infection of H. pylori. H. pylori causes chronic gastritis in the stomach and duopdenum, then later causing the formation of ulcers. Once diagnosed it is easily treatable with antibiotics and after positive eradication the re-infection rate is very low (only 1%).
(more information on stomach ulcers)