Typical symptoms of H. pylori are similar to those caused by gastritis or peptic ulcers, and they include a gnawing or burning abdominal pain that is worse when the stomach is empty and alleviated somewhat after eating, drinking milk or taking an antacid, according to WebMD. Other symptoms can include weight loss, bloating, burping, nausea, vomiting and black, tarry stools.
An H. pylori infection is diagnosed using an upper GI series, endoscopy, blood tests, stool test or urea breath test, according to WebMD. Causing up to 80 percent of stomach ulcers found in the upper end of the small intestine, H. pylori bacteria penetrates the stomach's mucous lining and weakens it, making it more susceptible to damage caused by gastric acid. Because the bacteria also attaches itself to the stomach, it causes inflammation of the stomach and can lead to the production of excess stomach acid.
It is not known how the bacteria is spread, but the leading theory in the scientific community is that it is spread through contaminated food and water, according to WebMD. In the United States, scientists believe that 20 percent of people under the age of 40 and half of people over the age of 60 are infected with the bacteria.