While the exact cause of H.pylori infections is not known, H.pylori bacteria has been known to exist for thousands of years. The bacteria are spread through contact with saliva or body fluids from infected people.
They may also be transferred from faeces to the mouth, which can happen if good hygiene is not observed – e.g. when the hands are not washed properly after using the washroom. Additionally, H. pylori may also spread through contact with contaminated water, food, or utensils.
H.pylori bacteria can cause the stomach mucous lining to weaken, making the stomach more vulnerable to harsh acids. Stomach acid, along with the bacteria, may irritate the stomach lining. It may also lead to the formations of sores (or ulcers) in the stomach or duodenum, which is the first part of the small intestine.

