Germs Can Cause Cancer. This Common Bacteria Leads to More Cases Than Any Other
H pylori bacterial infections can lead to gastric cancer and a type of lymphoma
- A report from the American Association for Cancer Research said a bacteria called H. pylori is the pathogen responsible for the highest number of global cancer cases.
- H. pylori accounted for over 800,000 cancer cases in 2018, and about 30% to 40% of Americans get an H. pylori infection at some point.
- Symptoms of an H. pylori infection include vomiting, weight loss, trouble swallowing, and severe heartburn—but infections may be asymptomatic.
When we think of what causes cancer, factors like genetics and lifestyle typically come to mind. But some pathogens can also lead to cancer diagnoses.
According to a recent report by the American Association for Cancer Research, 13% of cancer cases worldwide, or 2.2 million, are attributable to bacterial or viral infections. The culprits include hepatitis B, hepatitis C, and human papillomavirus, or HPV, the well-known cause of cervical cancer.
However, the pathogen responsible for causing the highest number of global cancer cases is one you may not be familiar with: Helicobacter pylori, more commonly known as H. pylori. The bacteria accounted for an estimated 810,000 cancer cases in 2018, the most recent year data is available. For comparison, HPV led to 690,000 cases that year, followed by hepatitis B, with 360,000 cases.
So what exactly is H. pylori? And how do you get it? Here’s what you need to know about the bacteria.
KATERYNA KON/SCIENCE PHOTO LIBRARY / Getty Images
What Is H. Pylori and How Does It Cause Cancer?
H. pylori is a bacteria that many people carry in their stomachs. Approximately 30% to 40% of people in the U.S. get an H. pylori infection at some point.
The bacteria can cause ulcers to form in the stomach or small intestine and can also lead to gastritis, which is inflammation of the stomach lining.
Over time, this can develop into more serious disease, said Linda Cummings, MD, a gastroenterologist at University Hospitals Cleveland Medical Center and professor of medicine at Case Western Reserve University School of Medicine. “In some people who are susceptible due to genetic factors, lifestyle, and/or characteristics of the H. pylori strain itself, this inflammation leads to pre-cancerous changes in the stomach lining that can eventually progress to cancer,” she told Health.
H. pylori can increase the risk of two types of cancer: mucosa-associated lymphoid tissue (MALT) lymphoma, a form of non-Hodgkin lymphoma that affects the stomach, and a type of gastric cancer called adenocarcinoma, which originates in the stomach lining. According to the American Cancer Society, 90 to 95% of all cancers of the stomach are adenocarcinomas.
H. pylori is the strongest risk factor for gastric cancer, Cummings noted. People with an H. pylori infection have a two- to six-fold increased risk of developing gastric cancer and MALT lymphoma compared with those who are uninfected, according to the Centers for Disease Control and Prevention.
It’s important to note, however, that for most people, having an H. pylori infection does not lead to cancer. “Among all people infected with H. pylori, it is believed that about 1% to 3% will develop cancer,” Cummings said.
How Do You Get H. Pylori?
While the transmission of H. pylori is not completely understood, Cummings said the bacteria may be spread via bodily fluids. “Since H. pylori can be found in stool, gastric juice, saliva, and dental plaques, it could potentially be spread from oral secretions or vomiting,” she said. “Household person-to-person transmission is likely because the risk of H. pylori in a child is higher if a parent or sibling is infected.”
Most people with H. pylori probably contract the infection in childhood, Cummings added. Transmission is often associated with poor hygiene and sanitation, crowded living conditions, and inadequate water supplies.
Overall, H. pylori infections are significantly more common in low-income and middle-income countries than in high-income nations like the United States.
But within the U.S., there are hotspots, including Indigenous American communities, where the H. pylori infection rate is higher than the 36% seen in the general population. H. pylori prevalence is 62% among Navajo adults in Arizona, for example, and 75% among the Alaska Native population.
Gastric cancer incidence is highest in East Asia, Eastern Europe, and Andean Latin America, while mortality is highest in East Asia, Andean Latin America, and Central Asia. “In some countries in Asia with high rates of gastric cancer, universal screening for gastric cancer is recommended with endoscopy or a radiographic test starting around age 40 or 50,” Cummings said.
Symptoms and Diagnosis
Some people with an H. pylori infection don’t have any symptoms, Cummings explained, while others might experience abdominal discomfort after eating. Vomiting, weight loss, trouble swallowing, and severe heartburn are also signs of an H. pylori infection.
“Stool that is black, foul-smelling, and increased in frequency may result from a bleeding ulcer caused by H. pylori,” Cummings added.
Because an H. pylori infection may be asymptomatic, testing is the only way to determine the bacteria’s presence. There are four ways to test for H. pylori: a urea breath test, a stool antigen test, an upper endoscopy, and a blood test. However, Cummings said the blood test is rarely used in the U.S. because a person may test positive even after the bacterial infection has been successfully treated.
Universal screening for H. pylori isn’t recommended in the U.S., but Cummings suggests testing for people who:
- Have signs or symptoms of an H. pylori infection
- Have or have had an ulcer in the stomach or small intestine
- Reside in the same household as someone who has an H. pylori infection
- Have a family history of H. pylori, gastric cancer, or peptic ulcer disease
- Have MALT or iron deficiency anemia
- Take non-steroidal anti-inflammatory drugs regularly, which increase the risk of ulcers
Treatment
According to Cummings, H. pylori infections typically don’t go away without treatment and have become increasingly challenging to treat because the bacteria has developed resistance to some antibiotics. “This resistance has led to more and more complex treatment regimens,” she said. “Nowadays, the infections are treated for two weeks with several medications, including acid-suppressing medications and antibiotics. Some regimens also include bismuth-containing compounds.”
Some people may need to take a second or even third regimen of antibiotics to eliminate the infection. While special testing can be done to determine which antibiotics H. pylori may be resistant to, Cummings said this testing isn’t widely available in the U.S.
How to Prevent an H. Pylori Infection
Because the transmission of H. pylori is not well understood and believed to be most often acquired in childhood, preventing the spread of the bacteria may be challenging.
Sharing a room has been linked to H. pylori transmission in children, so it’s possible that putting siblings in separate bedrooms may reduce the chance of transmission, Cummings said. “However, having a separate room may not be feasible, and having an infected sibling, infected mother, or infected father are each stronger risk factors for H. pylori than room sharing,” she noted.
Other strategies that may help to prevent the spread of H. pylori bacteria include washing your hands frequently, especially after bathroom use, avoiding sharing utensils and drinking glasses or bottles, and drinking water from a clean, safe source.
This story originally appeared on: Health News - Author:Elizabeth Yuko, PhD
