Helicobacter pylori is a spiral-shaped bacterium that infects the stomach lining, and it’s remarkably common. Around 44% of adults worldwide carry it. Most people never realize they’re infected because the majority of cases produce no symptoms at all. But in a significant minority, the infection leads to stomach ulcers, chronic inflammation, and in rare cases, stomach cancer.
How H. Pylori Survives in Your Stomach
Your stomach is one of the most hostile environments in the body, with acid strong enough to dissolve metal. H. pylori has evolved a clever workaround. The bacterium produces an enzyme that breaks down urea (a natural waste product in your body) into ammonia, which neutralizes the acid in its immediate surroundings. This creates a thin, pH-neutral bubble around the bacterium, letting it survive where almost nothing else can.
That same chemical trick also helps the bacterium move. Stomach mucus normally acts like a thick gel that traps microorganisms in place. But when H. pylori raises the pH around itself, the mucus shifts from a gel to a liquid, freeing the bacterium to swim through it and burrow into the stomach lining. Once embedded there, beneath the protective mucus layer, the infection can persist for decades if untreated.
How the Infection Spreads
H. pylori passes from person to person, most often within households. The primary routes are fecal-oral (through contaminated water or food) and through contact with vomit. A CDC-funded study found that exposure to vomit from an infected household member was the single biggest transmission risk, increasing the odds of new infection more than sixfold. Diarrheal illness in an infected contact also raised risk, though less dramatically.
Infection rates are highest in areas with crowded living conditions, limited access to clean water, and poor sanitation. In industrialized countries, rates have been declining for decades, but they remain high among disadvantaged and immigrant communities. Globally, prevalence in adults has dropped about 16% over the last three decades, from roughly 53% before 1990 to 44% in recent years. Among children and adolescents, though, the rate hasn’t budged significantly in any world region, sitting at about 35%.
Symptoms to Watch For
Most people with H. pylori have no symptoms whatsoever. When problems do develop, they typically stem from inflammation of the stomach lining (gastritis) or from a peptic ulcer that the infection has caused. Common symptoms include:
- A burning or aching pain in the upper abdomen, often worse on an empty stomach
- Bloating and frequent burping
- Nausea or loss of appetite
- Unexplained weight loss
More serious warning signs point to a bleeding ulcer or other complications. Black or tarry stools, vomiting blood or material that looks like coffee grounds, sharp sudden abdominal pain, dizziness, or unusual fatigue all warrant immediate medical attention.
Long-Term Complications
Left untreated for years or decades, chronic H. pylori infection raises the risk of several serious conditions. The most well-established link is to stomach cancer. People with long-standing infections have a higher risk of developing adenocarcinoma in the main body of the stomach. In parts of Asia where stomach cancer is especially common, the infection also increases risk of cancer in the upper portion of the stomach near the esophagus.
H. pylori is also strongly tied to a rare type of stomach lymphoma called MALT lymphoma. Nearly all patients diagnosed with this cancer show signs of H. pylori infection, and in many early-stage cases, simply eradicating the bacterium causes the lymphoma to regress. It’s worth emphasizing that while these risks are real, the vast majority of infected people never develop cancer. The bacterium is one risk factor among many, including genetics, diet, and smoking.
How It’s Diagnosed
Testing for H. pylori is straightforward and usually doesn’t require any invasive procedure. The most common non-invasive options are a urea breath test, a stool antigen test, or a blood test. Each has trade-offs.
The urea breath test is the most accurate of the three. You drink a solution containing a special form of urea, and if H. pylori is present, the bacterium breaks the urea down into carbon dioxide that can be detected in your breath. This test catches about 94% of infections at a 90% specificity threshold. The stool antigen test, which detects bacterial proteins in a stool sample, catches around 83% of cases. Blood tests (serology) fall in between at about 84% sensitivity, but they detect antibodies rather than active infection, so they can’t reliably confirm whether an infection has been successfully treated.
For people who need an endoscopy for other reasons (persistent symptoms, concern about ulcers), a small tissue sample from the stomach lining can confirm the diagnosis directly. This biopsy serves as the gold standard against which other tests are measured.
Treatment and the Resistance Problem
Treating H. pylori requires a combination of medications taken together, typically for 14 days. The current recommended first-line approach in the United States involves four drugs taken simultaneously: a proton pump inhibitor (a common acid-reducing pill) taken twice daily, plus three other medications including an antibiotic and bismuth (the active ingredient in Pepto-Bismol). This regimen is known as bismuth quadruple therapy.
The treatment landscape has shifted in recent years because of rising antibiotic resistance. The older, simpler three-drug regimen built around clarithromycin, which was once the go-to treatment, is no longer recommended unless lab testing has confirmed the bacterium is sensitive to that antibiotic. In many parts of the world, resistance to clarithromycin now exceeds 15%, and in some Asian countries it reaches over 90%. Resistance to another commonly used antibiotic class, fluoroquinolones, is similarly high in many regions. Metronidazole resistance is the most widespread globally, though the drug can still be effective at higher doses and longer treatment durations.
Alternative regimens exist for people who don’t respond to first-line treatment or who can’t tolerate certain medications. These include rifabutin-based therapy and newer combinations using vonoprazan, a more potent acid-suppressing drug, paired with amoxicillin. The key to successful treatment is completing the full course. Stopping early not only reduces the chance of clearing the infection but also contributes to the growing resistance problem.
Reducing Your Risk
There is no vaccine for H. pylori. Prevention comes down to basic hygiene measures: thorough handwashing, especially before preparing or eating food, and access to clean drinking water. Because transmission happens primarily within households, testing and treating infected family members can break the chain of spread, particularly when someone in the home has gastrointestinal symptoms.
Some dietary factors may offer modest protection. Cruciferous vegetables like broccoli, cauliflower, and cabbage contain compounds that appear to have activity against H. pylori in laboratory studies, and increasing intake of these foods is a reasonable, low-risk strategy alongside standard hygiene practices.