H. pylori Infection (Helicobacter pylori)

What H. pylori does in the stomach

The stomach is very acidic, but H. pylori has adapted to survive there. It burrows into the protective mucus layer and produces an enzyme called urease, which turns urea into ammonia and neutralizes acid around it. This is the basis of the urea breath test.

Once established, the bacterium causes ongoing inflammation of the stomach lining (chronic gastritis). Depending on which part of the stomach is most inflamed, it can:

• increase acid output, leading to duodenal ulcers
• damage the lining and reduce acid, leading over decades to atrophic gastritis, intestinal metaplasia and stomach cancer

The infection does not usually clear on its own and persists for life unless treated.

How H. pylori spreads

H. pylori is passed from person to person, most often in early childhood. Likely routes:

• oral-oral: saliva, shared utensils, pre-chewed food
• fecal-oral: contaminated water or food, poor sanitation
• within families: children of infected parents have higher rates

Risk is higher with crowded living conditions, lack of clean water, and in people born in countries with high rates, including parts of Latin America, Eastern Europe, Asia and Africa. In the US, rates are higher in older adults, Hispanic, Black, Native American and Alaska Native communities and immigrants from high-prevalence regions.

Is H. pylori contagious?

It is transmissible, but adults rarely acquire new infections. Spread between partners is uncommon. Good hygiene, such as handwashing and safe drinking water, lowers the risk. Partners or household members are not routinely tested unless they have symptoms or other reasons for testing.

Symptoms

Most infected people have no symptoms. When they occur, they are usually caused by gastritis or an ulcer:

• burning or gnawing pain in the upper belly, often worse when the stomach is empty
• bloating and belching
• nausea
• feeling full quickly
• loss of appetite

Signs of complications:

• black, tarry stools or vomiting blood (bleeding ulcer)
• tiredness and pale skin (iron-deficiency anemia)
• unexplained weight loss or trouble swallowing (possible cancer)

Complications

Who should be tested

Testing is recommended for people with:

• current or past peptic ulcer
• indigestion (dyspepsia), especially under age 60 without alarm features
• gastric MALT lymphoma
• a family member with stomach cancer
• unexplained iron-deficiency anemia
• immune thrombocytopenia
• long-term low-dose aspirin or NSAID use, especially with ulcer history
• early stomach cancer that has been removed
• family members living with someone who has active infection, in some cases

Anyone who tests positive should be treated, and a cure should be confirmed with a follow-up test. For details on tests, antibiotic regimens and confirming eradication, see H. pylori testing and treatment.

Prevention

There is no vaccine. Measures that may reduce risk:

• wash hands after using the toilet and before eating or preparing food
• drink clean, safe water
• avoid sharing utensils with people known to be infected
• avoid pre-chewing food for babies

Frequently asked questions

What are the symptoms of H. pylori?

Most people with H. pylori have no symptoms. When symptoms occur, they include burning or gnawing upper belly pain, bloating, belching, nausea, loss of appetite and feeling full quickly. Black stools or vomiting blood signal a bleeding ulcer and need emergency care.

How do you get H. pylori?

H. pylori is usually caught in childhood through saliva, contaminated food or water, or contact with an infected family member's stool. It is more common where sanitation is poor and in families where a parent is infected. Adults rarely catch it.

Is H. pylori contagious through kissing?

H. pylori can be present in saliva, so transmission through close contact is theoretically possible. However, new infections in adults are uncommon. Most infections are acquired in childhood within families.

Can H. pylori cause stomach cancer?

Yes. Long-term H. pylori infection is the strongest known risk factor for stomach cancer. Only a small percentage of infected people develop cancer, but treating the infection lowers the risk, especially when done before precancerous changes develop.

Can H. pylori go away on its own?

Rarely. Without treatment, H. pylori infection usually lasts for life. Antibiotic-based treatment cures most infections, and a follow-up test is recommended to confirm the bacteria are gone.