context: A common kind of bacteria called Helicobacter pylori, or H. pylori, can cause an infection in your stomach that sometimes leads to ulcers. It also can raise your risk of stomach cancer. H. pylori is a very common infection: More than half of all people get it at some point, usually in childhood. Doctors aren't sure why it affects some people differently than others. Most people with H. pylori infection don't know it and have no symptoms. Although it is not known exactly how H. pylori enters the body, researchers believe that the spiral-shaped bacteria probably get into your body through your mouth. Then, they burrow into the mucus that lines your stomach. You could pick up an H. pylori infection in several ways. The bug can be found in contaminated food or water. If a household member has H. pylori, it is more likely that others in the household also are infected. It has also been found in domesticated animals. H. pylori is much more common in parts of the world where there's poor sanitation, poverty, and overcrowding. H. pylori can inflame the lining of your stomach. That's why you may feel stomach pain or get nauseous. If it's not treated, it can sometimes cause ulcers, which are painful, open sores in your stomach lining that bleed. Studies show that people who are infected with H. pylori are also up to 8 times more likely to get a certain kind of stomach, or gastric, cancer. But this bacterium is only one possible cause of stomach cancer. Smoking, a diet low in fruits and veggies, and a history of stomach surgeries can raise your risk. H. pylori infections don't always cause symptoms. In fact, you may not feel sick at all. In some people, though, the infection may cause: Pain or burning in your gut Stomach pain that's worse if you haven't eaten No appetite Nausea Burping a lot Bloating or gas Unusual weight loss See your doctor right away if you notice the following in your child or yourself. They could be signs of an ulcer: Severe stomach pain that doesn't go away Inability to swallow Bloody, tar-like stool Vomit that's bloody or looks like dark coffee grounds If your doctor thinks you may have an H. pylori infection, some tests can tell you for sure: Endoscopy: The best way to test for H. pylori infection is to check your stomach lining. Your doctor will give you medicine to relax you. Then she'll send a long, thin tube with a camera on the end down your throat and into your stomach. She'll look for signs of infection and take a small sample of tissue from the lining. The sample will be tested in a lab to see if there's an infection. Blood tests: A simple blood test can show signs of H. pylori. But that doesn't mean the infection is active and causing problems or symptoms. Stool tests: Your doctor can test your poop for proteins that are a sign of H. pylori. This test can identify an active infection and can also be used to check that an infection has cleared after treatment. Your doctor probably will prescribe one or a combination of two antibiotics. Examples include amoxicillin, tetracycline, metronidazole, or clarithromycin. You'll take them for up to 2 weeks. Be sure to take all the pills in your prescription, even if you start to feel better. Your doctor also will prescribe medicine to help with stomach acid. It might include proton-pump inhibitors, H2 blockers, or bismuth subsalicylate ( Pepto- Bismol, Bismatrol). This medicine also helps your antibiotics work better because it calms inflammation in your stomach. About a month after you finish your antibiotics, your doctor can test for H. pylori to make sure it's gone. If there are still signs of the infection, you may need more antibiotics.