Helicobacter pylori is one of the most common chronic bacterial infections on the planet, currently carried by roughly 44 percent of the world’s adult population. That figure has dropped over the past three decades, down from nearly 60 percent in the 1980s, but it still means billions of people harbor this spiral-shaped bacterium in their stomach lining without necessarily knowing it. The story behind H. pylori’s prevalence is tied to how it spreads, where you live, how old you are, and how reliably it can be caught by modern testing.
How Prevalence Varies Around the World
Two large systematic reviews, drawing on studies from 1980 through 2022, paint a consistent picture of declining but still high global infection rates. One analysis estimated that global prevalence dropped from about 58 percent in the 1980–1990 period to roughly 43 percent in the 2011–2022 period, with a sharp decline particularly after 2011 and the largest regional drop in Africa.1PubMed. Global prevalence of Helicobacter pylori infection between 1980 and 2022: a systematic review and meta-analysis A second review reported a similar trajectory, placing the crude adult prevalence at about 44 percent for 2015–2022 and noting that children and adolescents still show infection rates around 35 percent.2PubMed. Global Prevalence of Helicobacter pylori Infection and Incidence of Gastric Cancer Between 1980 and 2022
The gap between wealthy and lower-income countries remains striking. In many developing nations, infection has historically been described as nearly universal, beginning in early childhood.3PubMed. Epidemiological features of Helicobacter pylori infection in developing countries Access to clean water, reduced household crowding, and better sanitation are the main forces driving prevalence down in the countries where it has fallen. In parts of sub-Saharan Africa, South Asia, and Latin America, the improvement has been slower. One estimate from the early 2000s put the total number of infected people above three billion worldwide, predominantly in developing regions.4PubMed Central. Helicobacter pylori infection in developing countries: the burden for how long?
What those regional numbers mean for you depends largely on where you grew up. If you spent your early childhood in a high-prevalence country, your odds of carrying the bacterium are far higher than if you were raised in Western Europe, North America, or Japan, where prevalence has dropped below 30 percent in many populations. H. pylori infection is usually acquired during childhood, and once established, it persists for life unless treated.
How H. Pylori Spreads
Despite decades of research, the exact transmission route is still debated. The most supported model is person-to-person spread, through either the oral-oral route or the fecal-oral route.5PubMed. Helicobacter pylori: epidemiology and routes of transmission Researchers have detected H. pylori DNA in saliva, dental plaque, vomit, gastric juice, and feces, which gives the bacterium several plausible ways to move between people.
Vomit appears to be a particularly efficient vehicle. A household study found that exposure to an infected family member who was vomiting was associated with a six-fold greater risk of new infection, while exposure to diarrhea alone did not raise the risk significantly.6Emerging Infectious Diseases. Gastroenteritis and Transmission of Helicobacter pylori Infection in Households The bacterium can be recovered from vomit in high concentrations and has even been cultured from aerosolized vomit collected at short distances. This makes gastroenteritis episodes within a household a plausible mechanism for spreading the infection to family members who were previously uninfected.
Water is the other major suspected route, especially in lower-income settings. Various types of water, including drinking water, wastewater, surface water, and groundwater, have been shown to harbor H. pylori.7PubMed. Quantification and cultivation of Helicobacter pylori (H. pylori) from various urban water environments: A comprehensive analysis of precondition methods and sample characteristics A study in northeastern Brazil found that drinking untreated water was associated with nearly triple the odds of carrying a particularly virulent strain of H. pylori.8PubMed. Helicobacter Pylori cagA+ Genotype is Associated With Consumption of Untreated Drinking Water in North-Eastern Brazil Contaminated water combined with poor sanitation is considered a key driver of the high infection rates seen in developing countries.9PubMed Central. Contaminated water as a source of Helicobacter pylori infection: A review
The Role of Families and Households
H. pylori clusters within families in a way that goes beyond shared environment. In a large study of 282 families in central China, about 87 percent of families had at least one infected member, and in roughly a third of infected families, genotyping confirmed that all members carried the same bacterial strain.10PubMed Central. Family-based Helicobacter pylori infection status and transmission pattern in central China, and its clinical implications for related disease prevention That same-strain finding is strong evidence for direct person-to-person transmission within the home rather than each family member picking up the bacterium independently from the outside environment.
Mothers appear to be the primary source of infection for young children. A five-year follow-up study tracked 44 children born to infected mothers and found that the 11 percent who became infected all carried strains genetically identical to their mothers’, with most infections acquired before age two.11PubMed Central. Five-year follow-up study of mother-to-child transmission of Helicobacter pylori infection detected by a random amplified polymorphic DNA fingerprinting method A community study of Japanese Brazilians showed that children whose mother was infected had about five times the odds of infection compared with children of uninfected parents, while having an infected father alone raised the odds much less. Pacifier use and the mother experiencing nausea and vomiting were additional risk factors, both consistent with the idea that regurgitated gastric contents are the primary vehicle.12PubMed. Community-based familial study of Helicobacter pylori infection among healthy Japanese Brazilians
Living conditions also matter. A study of children in the U.K. found that bed-sharing between children and parents raised the odds of infection roughly two to three times, even after adjusting for social class and household density.13PubMed Central. Helicobacter pylori infection in children: relation with current household living conditions This reinforces the general pattern: tight quarters and close physical contact during early childhood are the main conditions under which H. pylori moves between people.
How H. Pylori Is Detected
There are two broad categories of testing: invasive methods that require an endoscopy and biopsy, and noninvasive methods that do not. Each has trade-offs in accuracy, cost, and convenience.
Among noninvasive tests, the urea breath test and the stool antigen test are the workhorses. Both perform well in head-to-head comparisons against biopsy-confirmed diagnosis. One study comparing multiple methods found that the stool antigen test had a sensitivity of 96 percent and the urea breath test came in at 89 percent, both far outperforming blood antibody testing, which had a sensitivity of only about 50 percent.14PubMed Central. Diagnostic values of Helicobacter pylori diagnostic tests: stool antigen test, urea breath test, rapid urease test, serology and histology The breath test works by having you drink a solution containing labeled urea; if H. pylori is present, its urease enzyme breaks down the urea and the labeled carbon shows up in your exhaled breath. The stool antigen test detects bacterial proteins directly in a stool sample. Both are widely considered reliable enough to guide treatment decisions without requiring endoscopy.
Blood antibody tests (serology) are the cheapest and most widely available option, but they have a significant limitation: they cannot distinguish a current infection from a past one. Your body may keep producing antibodies long after successful treatment, which means a positive blood test does not necessarily mean you are still infected.15Indus Journal of Bioscience Research. Diagnostic Accuracy of Stool Antigen and Serological Tests for Helicobacter pylori Infection in Symptomatic Patients at a Tertiary Care Hospital in Islamabad For this reason, most guidelines now recommend the breath test or stool antigen test over serology when the goal is to confirm active infection or to check whether treatment has worked.
On the invasive side, the rapid urease test (sometimes called the CLO test) is performed on a tissue sample taken during endoscopy. A biopsy piece is placed in a solution containing urea and a pH indicator; if H. pylori’s urease enzyme is present, the solution changes color. This test gives results within hours and generally has high specificity, meaning false positives are rare.16The Indonesian Journal of Gastroenterology, Hepatology, and Digestive Endoscopy. Effectiveness of Rapid Urease Diagnostic Test in Diagnosing Helicobacter Pylori Infection in Patients with Dyspepsia in Gastrointestinal Endoscopy Centre Histology, where a pathologist examines the biopsy under a microscope, is often considered the reference standard, but it is more expensive and time-consuming. One practical limitation of any biopsy-based method is that H. pylori can be unevenly distributed across the stomach, so a random biopsy may miss the bacterium entirely.17PubMed Central. Endoscopic Diagnosis for H. pylori Infection: White Light Imaging (WLI) vs. Image-Enhanced Endoscopy (IEE)
For most people, the practical takeaway is straightforward: if your doctor suspects H. pylori, you will likely be offered either a breath test or a stool antigen test. Both are accurate, noninvasive, and can be used both for initial diagnosis and to confirm the infection is gone after treatment. Endoscopy is typically reserved for people who have alarming symptoms, have failed treatment, or need the procedure for other reasons.
What an Infection Can Do to Your Health
Most people with H. pylori never develop symptoms. The bacterium lives quietly in the stomach lining for decades in the majority of carriers. But in a minority, chronic infection leads to peptic ulcers and, more seriously, gastric cancer.18PubMed. Genetic battle between Helicobacter pylori and humans The World Health Organization classified H. pylori as a Group 1 carcinogen back in 1994, and it remains the single strongest known risk factor for stomach cancer. A rarer but well-documented consequence is gastric MALT lymphoma, a type of cancer of the immune tissue in the stomach wall that is closely associated with H. pylori infection and often regresses when the infection is treated.19PubMed. Helicobacter pylori and mucosa-associated lymphoid tissue: what’s new
The relationship between H. pylori and disease is not uniform. Which symptoms or complications develop depends partly on the strain you carry. Certain strains produce a protein called CagA, and these CagA-positive strains are more strongly linked to inflammation, ulcers, and cancer. The mix of virulence factors a given strain carries, including genes like vacA, oipA, and babA2, helps determine how aggressively the bacterium interacts with your stomach lining.20PubMed Central. Impact of Helicobacter pylori Virulence Genotypes cagA, vacA, oipA, and babA2 on Severity of Gastropathies in Brazilian Patients
Interestingly, some research suggests that H. pylori infection may protect against acid reflux disease, particularly in Asian populations. Studies have found a negative association between H. pylori infection and gastroesophageal reflux disease (GERD), possibly because certain virulent strains reduce stomach acid output over time.21PubMed. Does Helicobacter pylori infection protect against esophageal diseases in Asia? This creates an uncomfortable paradox: the same strains most associated with stomach cancer may be the ones most protective against acid reflux and the esophageal problems that come with it. It is one reason why the question of whether to screen and treat everyone for H. pylori, even in the absence of symptoms, remains genuinely complicated.
Why Reinfection Rates Differ So Much by Setting
Once H. pylori is successfully eradicated, the chance of getting reinfected varies enormously depending on where you live. A meta-analysis of reinfection studies found an annual recurrence rate of about 1.5 percent in developed countries compared with 12 percent in developing countries.22PubMed. Helicobacter pylori recurrence in developed and developing countries: meta-analysis of 13C-urea breath test follow-up after eradication That eight-fold gap largely comes down to the same factors driving initial infection: sanitation, water quality, and household crowding. If the conditions that allowed you to become infected in the first place have not changed, eradication of the bacterium may be a temporary fix.
The distinction between true reinfection (catching a new strain from the environment) and recrudescence (the original strain coming back because treatment did not fully clear it) is hard to make without strain-level genetic testing, which is rarely done in routine clinical care. In low-recurrence settings, many apparent reinfections may actually be recrudescence. In high-recurrence settings, genuine reinfection with a new strain is more likely because exposure is ongoing. For people living in high-prevalence areas, this raises a practical question about the long-term value of treatment in the absence of symptoms: if there is a one-in-eight chance per year of getting infected again, the benefit-to-burden calculation shifts compared with a setting where recurrence is rare.
Antibiotic Resistance Is Reshaping Treatment
Standard H. pylori treatment involves a combination of antibiotics and an acid-suppressing drug, typically taken for 10 to 14 days. The regimens have historically worked well, but resistance is now a serious and growing problem. A 2025 global analysis found that resistance to clarithromycin, one of the most effective drugs against H. pylori, exceeded 15 percent in 24 of 31 countries studied. Resistance to levofloxacin, another commonly used drug, crossed the same threshold in 18 of 31 countries.23PubMed. Helicobacter pylori antibiotic resistance: a global challenge in search of solutions When resistance rates climb above 15 percent in a region, the guidelines generally say clinicians should stop using that antibiotic as a first-line option, because it will fail too often to be worth the side effects and cost.
The problem is not limited to adults. Rising antibiotic resistance among children carrying H. pylori has been detected in most WHO regions, a trend that has prompted calls for more urgent action.24PubMed Central. Global prevalence of Helicobacter pylori antibiotic resistance among children in the world health organization regions between 2000 and 2023: a systematic review and meta-analysis Part of the issue is the widespread use of these same antibiotics for other common infections, particularly respiratory illnesses, which breeds resistance in H. pylori as a bystander effect. If you have previously taken clarithromycin or a fluoroquinolone for a different condition, any H. pylori in your stomach may have already developed partial resistance, reducing the chances of eradication on a standard regimen.
What Eradication Treatment Does to Your Gut
Wiping out H. pylori typically requires potent antibiotics that do not only kill the target bacterium. A review of the evidence found that eradication therapy alters the broader gut microbiome within a short period, and most of those changes take a long time to reverse.25PubMed Central. Impact of Helicobacter pylori infection on gut microbiota The antibiotics and acid-suppressing drugs used in standard regimens reduce some bacterial groups while allowing others to expand. One study in young adults observed a decrease in one major group of gut bacteria (Bacteroidetes) and a corresponding increase in another (Firmicutes) after H. pylori eradication, along with a rise in bacteria that produce short-chain fatty acids.26PLoS ONE. Helicobacter pylori Eradication Causes Perturbation of the Human Gut Microbiome in Young Adults Shifts in these bacterial populations have been linked in other research to metabolic changes, though the clinical significance of this particular disruption is still unclear.
For most people, the microbiome disruption from a two-week course of antibiotics is temporary and worthwhile if it clears an infection that carries cancer risk. But it is part of the reason many gastroenterologists do not rush to treat H. pylori when there are no symptoms and no other risk factors. The decision to treat weighs the long-term cancer-prevention benefit against short-term side effects, potential for reinfection, and the broader consequences of antibiotic use in a world where resistance is climbing fast.
An Ancient Companion With a Modern Footprint
H. pylori is not a recent arrival in the human body. Genetic analysis of bacterial strains from populations around the world shows that H. pylori has been co-evolving with humans for at least 60,000 years, migrating out of Africa alongside its hosts and diversifying into seven distinct genetic populations that correspond to major human migration routes.27PubMed Central. Evolutionary History of the Helicobacter pylori Genome: Implications for Gastric Carcinogenesis Researchers can use H. pylori strains as a molecular record of human movement: the strains found in Indigenous populations of the Americas, for example, retain genetic signatures tracing back through Siberia.28PubMed Central. Helicobacter pylori’s historical journey through Siberia and the Americas
This deep evolutionary relationship has led some researchers to argue that H. pylori should not be viewed as a straightforward pathogen. For most of human history, virtually everyone carried the bacterium, and it is only in the last century or so that improved sanitation has begun to drive it out of wealthy populations. Whether the disappearance of H. pylori from those populations has its own health consequences, including the possible loss of the protective effect against acid reflux, remains an active area of research. It is a question that does not lend itself to a simple answer, but it helps explain why the global public-health strategy for H. pylori is about targeted treatment and cancer prevention rather than mass eradication of a microbe that has lived in human stomachs since before recorded history.