Most people with H. pylori infection will never have any signs or symptoms. It's not clear why this is, but some people may be born with more resistance to the harmful effects of H. pylori.

When signs or symptoms do occur with H. pylori infection, they may include:

• An ache or burning pain in your abdomen
• Abdominal pain that's worse when your stomach is empty
• Nausea
• Loss of appetite
• Frequent burping
• Bloating
• Unintentional weight loss

The exact way H. pylori infects someone is still unknown. H. pylori bacteria may be passed from person to person through direct contact with saliva, vomit or fecal matter. H. pylori may also be spread through contaminated food or water.

H. pylori is often contracted in childhood. Risk factors for H. pylori infection are related to living conditions in your childhood, such as:

• Living in crowded conditions. You have a greater risk of H. pylori infection if you live in a home with many other people.
• Living without a reliable supply of clean water. Having a reliable supply of clean, running water helps reduce the risk of H. pylori.
• Living in a developing country. People living in developing countries, where crowded and unsanitary living conditions may be more common, have a higher risk of H. pylori infection.
• Living with someone who has an H. pylori infection. If someone you live with has H. pylori, you're more likely to also have H. pylori.

Complications associated with H. pylori infection include:

• Ulcers. H. pylori can damage the protective lining of your stomach and small intestine. This can allow stomach acid to create an open sore (ulcer). About 10 percent of people with H. pylori will develop an ulcer.
• Inflammation of the stomach lining. H. pylori infection can irritate your stomach, causing inflammation (gastritis).
• Stomach cancer. H. pylori infection is a strong risk factor for certain types of stomach cancer.