How Common Is H. Pylori? Global Rates and Risks

Roughly 44% of the world’s adult population carries Helicobacter pylori, a spiral-shaped bacterium that colonizes the stomach lining and can persist for decades without symptoms. That figure, drawn from the most recent large-scale analyses, represents a meaningful decline from rates above 50% measured before the 1990s, but it still means more than three billion people are walking around with an active infection right now. The story behind that number is more layered than a single global percentage suggests, because where you live, how you grew up, and which strain you carry all shape what the infection means for your health.

The Global Picture and How It Has Changed

Two major systematic reviews published in 2023 traced H. pylori prevalence across four decades. One, covering studies from 1980 through 2022, found that the estimated global rate fell from about 58% in the 1980–1990 period to roughly 43% in the 2011–2022 period, with rates holding fairly steady through the 1990s and 2000s before dropping sharply in the most recent decade.¹ A second analysis, focused on adults specifically, placed the decline at a similar trajectory: from about 53% before 1990 down to 44% in the 2015–2022 window.²

The decline is not evenly distributed. Improved sanitation, cleaner water supplies, smaller household sizes, and wider antibiotic use in wealthier countries have driven rates down fastest in those settings. But in much of the developing world, prevalence remains stubbornly high, meaning the global average masks an enormous gap between populations.

Rates Vary Wildly by Region and Country

Africa consistently reports the highest infection rates. One earlier meta-analysis put the continent’s pooled prevalence at about 70%, with Nigeria reaching nearly 88%.³ More recent data from a 27-country study confirmed the pattern: South Africa topped the list at 95%, followed by Benin at 86%, while the United States sat at about 27%, Norway at 26%, and Malaysia at just 14%.⁴ Oceania, which includes Australia and New Zealand, consistently shows the lowest regional prevalence, around 24%.³

Latin America sits somewhere in the middle-to-high range, with Chile at roughly 75% and Brazil above 70%.⁴ East Asian countries like Japan and South Korea have historically had high rates too, which is one reason gastric cancer screening programs are so well established there.

When and How People Get Infected

Most H. pylori infections are picked up in childhood, and in high-prevalence settings the window is early. A birth-cohort study in Bangladesh found that most children who became colonized did so after their first year of life, and that in developing countries more than half of children are infected before age ten.⁵ In a study of Ethiopian children, about 53% tested positive at baseline, and nearly all remained positive at follow-up years later, illustrating how persistent the bacterium is once it takes hold.⁶

In wealthier settings, childhood acquisition rates are far lower. A German birth-cohort study found only 3% of four-year-olds were infected. Mothers turned out to be the dominant source: having an infected mother raised a child’s odds of infection roughly thirteenfold after accounting for other family members.⁷

The bacterium spreads through several routes, primarily fecal-oral and oral-oral contact.⁸ Contaminated water and food, shared utensils, and close household contact all play roles. This is why the social determinants of health matter so much for H. pylori: a meta-analysis of those factors found that household overcrowding raised infection odds by about 38%, and occupational instability raised them by about 23%. People with low education levels were roughly three and a half times more likely to be infected compared to those with the highest education.⁹ Even within a single country, social class creates a gradient. In a large British study, infection rates ran from 22% in the highest social class to 38% in the lowest, with manual workers carrying higher risk than non-manual workers even after adjusting for other factors.¹⁰

How H. Pylori Survives in Your Stomach

The stomach is one of the harshest environments in the human body, drenched in hydrochloric acid at a pH low enough to dissolve metal. H. pylori has a trick for surviving it: an enzyme called urease that breaks down urea into ammonia, effectively neutralizing the acid in its immediate surroundings. This creates a small chemical buffer zone that lets the bacterium burrow into the mucus layer lining the stomach wall and settle in comfortably.¹¹

Once established, the bacterium produces proteins that help it persist and cause damage. Two of the most studied are CagA and VacA, toxins that interfere with the cells lining the stomach in different ways. CagA gets injected directly into stomach cells, while VacA is secreted into the surrounding environment. Both come in multiple genetic variants, and the specific combination a person carries helps explain why some infected individuals develop serious disease while others go decades without symptoms.¹² Strains that are CagA-positive tend to provoke more inflammation and are linked to a higher risk of peptic ulcers. The VacA s1 subtype independently correlates with more extensive chronic inflammation too.¹³

The Diseases It Causes

Most people with H. pylori never develop symptoms. Of those who do, the range runs from mild chronic gastritis to peptic ulcers to, in a small fraction, stomach cancer. H. pylori can be found in 90–100% of patients with duodenal ulcers and 60–100% of those with gastric ulcers.¹⁴ That finding, which earned Barry Marshall and Robin Warren the Nobel Prize in 2005, upended the old assumption that ulcers were caused by stress or spicy food.

H. pylori is also the strongest recognized risk factor for gastric adenocarcinoma, the most common form of stomach cancer. The bacterium sets off a chronic inflammatory process in the stomach lining that can progress through stages over decades, eventually leading to cancerous changes in a subset of patients.¹⁵ It is worth emphasizing that most infected people never get stomach cancer. The bacterium is necessary but not sufficient: host genetics, diet, smoking, and bacterial strain all factor in.

A less well-known association is with gastric MALT lymphoma, a type of B-cell lymphoma that develops in the stomach’s immune tissue. This cancer accounts for roughly 7–9% of all B-cell lymphomas. Remarkably, early-stage gastric MALT lymphoma can go into complete remission in about 60–90% of cases simply by eradicating the H. pylori infection with antibiotics, no chemotherapy needed.¹⁶ That is a striking example of how deeply the bacterium’s presence drives certain diseases: remove it, and the cancer regresses on its own.

Effects Beyond the Stomach

H. pylori’s influence does not stop at the stomach wall. Persistent infection can lead to iron deficiency and iron-deficiency anemia, particularly in children and teenagers. The mechanism involves both reduced acid secretion (which impairs iron absorption) and competition for iron by the bacterium itself. In some cases, the anemia is recurrent or resistant to iron supplements until the infection is treated.¹⁷

Researchers have also documented associations with vitamin B12 deficiency anemia, primary immune thrombocytopenia (a condition where the immune system attacks platelets), and a range of skin and eye conditions.¹⁸ The strength of evidence varies across these conditions, and for many of them the relationship is an observed association rather than a proven cause. Still, the pattern is consistent enough that guidelines now recommend testing for H. pylori when certain types of unexplained anemia or low platelet counts show up.

There is also growing interest in how H. pylori reshapes the broader gut microbiome. Because the infection changes stomach acidity over time, it alters the environment that downstream bacteria encounter. Research has shown shifts in the relative abundance of bacterial groups like Lactobacillus and Streptococcus in people with H. pylori-driven atrophic gastritis, a condition where the stomach lining thins and acid production drops.¹⁹ These changes in microbial diversity may contribute to the cancer pathway: a disturbed gastric microbiome has been linked to the progression toward gastric carcinoma.²⁰

How It Is Diagnosed

There are two broad categories of H. pylori testing: invasive methods that require an endoscopy, and non-invasive methods that do not. Non-invasive options include the urea breath test (you drink a solution and breathe into a collection device), the stool antigen test (a lab checks your stool sample for H. pylori proteins), and blood serology (which detects antibodies but cannot distinguish a current infection from a past one). The breath test and stool test both perform well, with sensitivity and specificity above 95% in studies comparing them head to head.²¹

Invasive tests involve taking a small tissue sample during endoscopy and either running a rapid urease test on it or examining it under a microscope. A comparative study of five diagnostic methods found that invasive tests generally outperformed non-invasive ones, though the margins were modest for the best non-invasive options.²² Serology, by contrast, performed poorly in some settings, with sensitivity and specificity hovering around 50%.²³ In practice, most doctors reach for the breath test or stool antigen test first unless there is another reason to do an endoscopy, like alarming symptoms or a need to rule out cancer.

Treatment and the Antibiotic Resistance Problem

Standard H. pylori treatment uses a combination of antibiotics plus an acid-reducing medication, taken for one to two weeks. The classic approach was a triple therapy built around clarithromycin. But resistance to clarithromycin has been climbing worldwide, now exceeding 15% in the majority of countries surveyed.²⁴ Levofloxacin resistance has followed a similar trajectory. In parts of the United States, clarithromycin resistance rates have reached above 20%, and metronidazole resistance is even higher in some regions.²⁵ The trend is toward rising resistance across all age groups, with adults showing higher resistance rates than children.²⁶

This is why quadruple therapy, which adds bismuth (the active ingredient in Pepto-Bismol) to the mix, has become the preferred first-line approach in many regions. A meta-analysis in Asian adults found quadruple therapy achieved about 21% higher likelihood of successful eradication compared to triple therapy.²⁷ In areas with high clarithromycin resistance, bismuth quadruple therapy is now recommended over clarithromycin triple therapy as the empiric first-line choice.²⁸ A randomized trial comparing the two in patients with confirmed clarithromycin resistance found that 14-day bismuth quadruple therapy achieved a per-protocol eradication rate of about 95%, compared to 76% for intensified triple therapy.²⁹

Adding probiotics to standard antibiotic treatment has shown promise as well. Multiple meta-analyses have found that probiotic supplements modestly improve eradication rates and roughly cut the incidence of side effects like diarrhea and nausea in half.³⁰ Specific strains like Saccharomyces boulardii and certain Lactobacillus species appear most effective. Probiotics alone will not clear the infection, but they may help people tolerate the antibiotic regimen well enough to complete it, which matters because unfinished courses are a major driver of treatment failure and further resistance.³¹

Can Mass Screening Prevent Stomach Cancer?

Given that H. pylori is the dominant risk factor for gastric cancer, the logical public-health question is whether screening entire populations and treating everyone who tests positive would cut cancer rates. Two large randomized trials have now weighed in, and the results are cautiously encouraging.

A community-level cluster-randomized trial found that people who received anti-H. pylori therapy had a modest reduction in gastric cancer incidence, with a stronger benefit in those whose infections were actually eradicated successfully.³² A separate pragmatic trial in Taiwan found that after adjusting for population differences, the screened-and-treated group had a statistically lower gastric cancer incidence, though the unadjusted comparison did not quite reach significance and gastric cancer mortality was not reduced.³³

These trials suggest that mass screening could bend the curve on gastric cancer at the population level, but the benefits are not dramatic in the short to medium term, and they depend heavily on actually clearing the infection. In high-prevalence regions where gastric cancer is common, the case for broad screening is strongest. In lower-prevalence settings like the U.S. or Northern Europe, targeted testing of higher-risk groups (immigrants from high-prevalence countries, people with a family history of stomach cancer, those with unexplained dyspepsia) is the current approach.

A Bacterium That Has Traveled with Humans for Millennia

H. pylori is not a recent arrival. Genomic studies indicate the bacterium left Africa alongside early humans roughly 60,000 years ago and has been co-evolving with us ever since. Over those millennia, it diverged into at least seven distinct genetic populations whose geographic distributions mirror major human migrations across continents.³⁴ Researchers have used H. pylori strains as molecular tracers to reconstruct human migration patterns, particularly into East Asia.³⁵

This deep evolutionary partnership is part of why some researchers argue H. pylori should not be viewed purely as a pathogen. In populations where the bacterium has been present for tens of thousands of years, some strains appear relatively benign, while the most virulent strains (particularly those carrying CagA variants common in East Asia) emerged in specific geographic lineages. The mismatch between a host population’s genetic background and the H. pylori strains circulating in their region may help explain puzzles like the “African enigma,” the observation that many African countries have extremely high H. pylori rates but relatively low gastric cancer rates compared to East Asia. Strain genetics, host genetics, and dietary factors all contribute, and untangling their individual roles remains an active area of research.