This simple stomach bug can cause stomach cancer if left untreated

What starts as a seemingly harmless stomach bug could quietly set the stage for something far more sinister. A stomach bug, which is commonly found, if untreated can lead to stomach cancer. What makes this bug even more dangerous is only 20% of those infected show symptoms, and it does not cause illness in most people The bacteria in question is H. pylori. These bacteria are present in some 50% to 75% of the world’s population. In the US, H. pylori bacteria are found in about 5% of children under the age of 10. Before we delve into how the stomach bug causes cancer, let’s take a look at what it is.

What is H. pylori?

Helicobacter pylori (H. pylori) is a spiral-shaped bacterium that grows in the mucus layer that coats the inside of the human stomach. Though most bacteria cannot survive in the acidic environment in our stomach, this bacterium can neutralize the local environment and thrive.

H. pylori can cause an infection in the stomach or duodenum (the first part of the small intestine). This bacteria is the main cause of peptic ulcers. H.pylori can also spread from person to person through saliva, plaque on teeth, and poop.

For most people, H. pylori infection won’t cause any problems and hence treatment is not requireed. However, in some, it can be a cause of persistent indigestion, bloating or nausea.

H. pylori and cancer

This sneaky little bug doesn’t always announce itself. While some develop mild symptoms, others do not. However, over time it can stir up bigger problems. If the symptoms are left unchecked it can lead to chronic inflammation in the stomach, a condition called gastritis. This irritation can erode the stomach lining, sometimes causing ulcers. This bug can also cause certain types of stomach cancers, particularly gastric adenocarcinoma and gastric mucosa-associated lymphoid tissue (MALT) lymphoma, which is a rare type of non-Hodgkin lymphoma. Studies suggest that chronic H. pylori infection causes gastric adenocarcinoma and gastric MALT lymphoma, leading to cancer.

In 1994, this bug was classified as a human carcinogen, by the World Health Organization’s International Agency for Research on Cancer. Later in 2021, the National Toxicology Program’s 15th Report on Carcinogens added chronic infection with H. pylori to its list of substances that are known or reasonably anticipated to cause cancer in humans.

How to know if you are at risk?

Dr. Saurabh Sethi, a Harvard and Stanford-trained Gastroenterologist has recently shared about treating a patient with stomach cancer, infected with H. pylori. He treated a patient with a distended abdomen and difficulty in food passage due to a stomach blockage.


"I treated a patient with extended abdomen and difficulty in food passage stomach blockage,” Dr. Sethi shares in his Instagram post. The gastroenterologist performed an endoscopy and placed a metal stent in the stomach. The biopsy revealed the H. pylori bacteria. “Unfortunately the stomach cancer has advanced to the point where a surgical intervention is necessary involving removal of half of the patient's stomach,” he said. The doctor also advised to get checked for H. pylori if persistent heartburn or indigestion symptoms appear.

The Centers for Disease Control and Prevention (CDC) recommends people with an active gastric or duodenal ulcers or a documented history of ulcers should be tested for H. pylori.