Question: are all ulcers caused by h pylori?
Answer: pylori causes almost all peptic ulcers, accounting for 80 percent of stomach ulcers and more than 90 percent of duodenal ulcers. H. pylori infection is common in the United States: about 20 percent of people under 40 and half of people over 60 are infected with it. Most infected people, however, do not develop ulcers.