Helicobacter pylori: The Common Bacteria Behind Gastritis and an Increased Risk of Stomach Cancer

Helicobacter pylori, often shortened to H. pylori, is one of the most common bacterial infections in the world. Around half of the global population carries this spiral shaped bacterium, yet many people never realise they are infected. While it often causes no symptoms, H. pylori is the leading cause of chronic gastritis and is strongly associated with peptic ulcers and an increased risk of stomach cancer.

The discovery of the connection between H. pylori and stomach disease transformed modern medicine. Before the early 1980s, doctors believed that stress, spicy foods, and excess stomach acid were the primary causes of ulcers. Today, we know that a bacterial infection is responsible for the majority of cases, allowing millions of people to receive effective treatment and significantly reducing the risk of serious complications.

What Is Helicobacter pylori?

Helicobacter pylori is a type of bacteria that survives in the acidic environment of the stomach. Unlike most bacteria, it has evolved unique mechanisms that allow it to live beneath the protective mucus lining of the stomach wall. It also produces an enzyme called urease, which helps neutralise stomach acid around the bacteria, making survival possible.

Researchers estimate that approximately 50% of the world's population is infected with H. pylori, although infection rates vary significantly depending on age, sanitation, living conditions, and geographic location. In many developed countries, infection rates are lower among younger people but increase with age.

Most infections occur during childhood. Once acquired, the bacteria can remain in the stomach for decades unless treated with antibiotics.

How Does H. pylori Spread?

Scientists believe H. pylori spreads mainly through close personal contact. The bacteria may pass from person to person through saliva, particularly between family members or from mothers to children during early childhood.

In areas with poor sanitation, contaminated food or water may also contribute to transmission, although this route has not been fully confirmed.

Because infection often happens early in life and causes few immediate symptoms, many people carry the bacteria for years without knowing it.

How H. pylori Causes Gastritis

Gastritis refers to inflammation of the stomach lining. When H. pylori colonises the stomach, it triggers a long term immune response that causes ongoing inflammation.

For many people, this chronic gastritis remains mild and symptom free. Others may experience symptoms such as:

• Burning or gnawing stomach pain
• Nausea
• Bloating
• Feeling full quickly
• Loss of appetite
• Indigestion

The inflammation may continue for many years, gradually damaging the stomach lining.

From Gastritis to Ulcers

One of the most important discoveries involving H. pylori was its role in causing peptic ulcers.

Peptic ulcers are open sores that develop in the stomach or the upper part of the small intestine. Persistent inflammation weakens the protective lining, allowing stomach acid to damage the tissue underneath.

Before H. pylori was identified, ulcers frequently returned despite treatment. Today, eliminating the bacterial infection with antibiotics can cure many ulcers permanently and prevent recurrence.

This groundbreaking discovery earned Australian researchers Robin Warren and Barry Marshall the 2005 Nobel Prize in Physiology or Medicine.

The Link Between H. pylori and Stomach Cancer

Perhaps the most serious complication of H. pylori infection is its association with stomach cancer.

Long standing inflammation caused by the bacteria can gradually damage stomach cells. Over many years, repeated injury and repair increase the likelihood of genetic changes that may eventually lead to cancer.

Research suggests that more than 90% of gastric adenocarcinoma cases are linked to H. pylori infection. Gastric adenocarcinoma is the most common type of stomach cancer and remains one of the leading causes of cancer related deaths worldwide.

Fortunately, identifying and treating H. pylori before significant damage occurs can substantially reduce the future risk of developing stomach cancer.

The infection is also associated with a rare cancer of the immune system called MALT lymphoma, which often responds well when the bacterial infection is successfully treated.

Who Should Be Tested?

Not everyone with H. pylori requires immediate testing, but healthcare providers commonly recommend testing for people who have:

• Persistent stomach pain
• Symptoms of indigestion that do not improve
• A history of stomach ulcers
• Unexplained iron deficiency anaemia
• Certain types of vitamin B12 deficiency
• A family history of stomach cancer in some situations

Anyone experiencing persistent digestive symptoms should seek medical advice rather than attempting to self diagnose.

How Is H. pylori Diagnosed?

Doctors can diagnose H. pylori using several reliable tests.

Breath Test

A urea breath test is considered one of the most accurate non invasive methods. Patients drink a special solution, and if H. pylori is present, the bacteria produce carbon dioxide that can be detected in the breath.

Stool Test

A stool antigen test identifies proteins from the bacteria in a stool sample and is commonly used to confirm both infection and successful treatment.

Blood Test

Blood tests detect antibodies against H. pylori. However, because antibodies can remain after the infection has cleared, blood testing is less useful for confirming active infection.

In some cases, doctors may perform an endoscopy with biopsy, particularly if symptoms are severe or stomach cancer needs to be ruled out.

Treatment Options

Unlike many bacterial infections, H. pylori usually requires combination therapy.

Treatment commonly includes:

• Two or three antibiotics
• A proton pump inhibitor (PPI) to reduce stomach acid
• Occasionally an additional medication that helps protect the stomach lining

The full treatment course usually lasts between 10 and 14 days.

Reducing stomach acid allows the antibiotics to work more effectively while helping the stomach lining heal.

Antibiotic Resistance Remains a Challenge

One growing concern is antibiotic resistance.

Like many bacteria, H. pylori has developed resistance to several commonly used antibiotics in some regions. As a result, the first treatment may not always eliminate the infection completely.

If initial therapy fails, doctors often prescribe an alternative combination of antibiotics. Follow up testing is usually recommended several weeks after treatment to confirm the infection has been eradicated.

Why Early Detection Matters

Most people infected with H. pylori never develop serious illness. However, because the infection can silently cause inflammation for many years, early diagnosis and treatment offer important long term health benefits.

Successful treatment can:

• Cure many peptic ulcers
• Prevent ulcer recurrence
• Reduce chronic stomach inflammation
• Lower the risk of developing stomach cancer
• Improve quality of life for people with ongoing digestive symptoms

The discovery of H. pylori fundamentally changed the understanding of digestive disease. What was once believed to be caused mainly by stress is now recognised as a treatable bacterial infection, improving outcomes for millions of patients worldwide.

Conclusion

Helicobacter pylori remains one of the world's most widespread bacterial infections. Although many people experience no symptoms, the bacteria are the leading cause of chronic gastritis and play a major role in peptic ulcers and stomach cancer.

Awareness, early diagnosis, and appropriate treatment have dramatically reduced the burden of these conditions over recent decades. Anyone experiencing persistent stomach pain, indigestion, or ulcer symptoms should speak with a healthcare professional to determine whether H. pylori testing is appropriate.

Source

This article is based on information originally published by The Conversation in an article by Phil Sutton, first published in 2018 and republished in 2026 following renewed public interest in gastritis.

Disclaimer

This content is for informational and educational purposes only and should not be considered medical advice. It is not intended to diagnose, treat, cure, or prevent any disease. Always consult a qualified healthcare professional regarding symptoms, diagnosis, testing, or treatment options for Helicobacter pylori, gastritis, or any other medical condition.