Surprising culprit tied to 1 in 8 cancer cases worldwide, major study reveals

About one in eight new cancer cases worldwide in 2024 — 2.3 million cases — have been linked to infections, according to a new analysis from the International Agency for Research on Cancer (IARC).

The researchers identified 12 specific infections that were linked to human cancer cases, including Helicobacter pylori (H. pylori), human papillomavirus (HPV), hepatitis B virus (HBV), hepatitis C virus (HCV), Epstein–Barr virus (EBV), Kaposi sarcoma-associated herpesvirus, Schistosoma haematobium, HTLV-1, Opisthorchis viverrini, Clonorchis sinensis, Merkel cell polyomavirus and HIV.

The following five infections contributed to nearly all the global cases.

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"The findings underscore the major role that infection control can play in reducing the global cancer burden," said study co-author Dr. Harriet Rumgay, a scientist in the Cancer Surveillance Branch at IARC, in a press release.

"Despite progress in vaccination and screening, infection-related cancers remain a major global challenge, with the burden falling disproportionately on populations in low- and middle-income countries."

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The researchers say many of these cancers could have been prevented through vaccination, treatment or screenings.

The study, conducted in France, analyzed cancer data from 2024. The findings were published in The Lancet Oncology on Sept. 28.

The study had several limitations, the researchers acknowledged.

Because the study used population-level estimates rather than tracking individual patients over time, the results depended on the quality of available cancer data in each country.

Additionally, it only included infections already proven to cause cancer, so the total impact could be underestimated.

"We know that there are certain infections that we are exposed to over our lifetime that may result in an increased risk of certain cancers," Dr. Joshua Cohen, medical director of the Gynecologic Cancer Program of City of Hope Orange County in Irvine, California, told Fox News Digital.

"However, most cancers are not caused by infection."

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HPV is one of the most common drivers of cancers that arise along the rectum, vagina or cervix, as well as the oropharynx (back of the throat), according to Cohen, who was not involved in the study.

"Eighty percent of the population has been exposed to certain types of HPV strains," he said. "About 40,000 people in the U.S. are diagnosed with these cancers each year."

For most people who are exposed to HPV, the body will clear the virus on its own, Cohen said.

"We don't know why some patients' immune systems allow them to clear the HPV infection and some don't."

Another very common cancer, although less so in the U.S., is gastric cancer, he noted, which is linked to H. Pylori, an infection in the stomach.

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"We don't screen everybody for H. pylori in the U.S. — it's more common in other parts of the world, like Southeast Asia."

However, those who have peptic ulcer disease or significant epigastric pain should talk with a gastroenterologist about getting screened and treated for H. pylori, the doctor advised.

There are things people can do to reduce the risk of infection-related cancers, according to Cohen.

"As a patient, the most important thing is to think about your health, what you can do to prevent yourself from developing these infections or your family," he said.

"And if you do have one of these infections, what can you do to reduce your risk of developing a subsequent cancer?"

Cohen emphasized that Americans have access to an HPV vaccination that can help prevent many of these infections.

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"If you’re under the age of 45 and you've not had an HPV vaccination, there is various good safety data that you should get vaccinated," he said. "That will cover, at least in the U.S., most risks regarding oropharyngeal cancers, vaginal cancers, cervical cancers, penile cancers and anal cancers."

The doctor reiterated that developing one of the listed infections doesn’t necessarily mean someone will develop cancer.

"The vast majority of patients who have an HPV infection or H. Pylori, or even hepatitis B or C, are not going to develop cancer," he said.

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But because these infections have been associated with certain cancers, it’s important to seek treatment for them.

Symptoms such as epigastric pain (pain or discomfort in the upper middle part of your abdomen), acid reflux, abnormal vaginal bleeding or pain with swallowing could be related to medical conditions that may be associated with certain infections or cancer, the doctor warned.

"There are steps we can take as doctors to keep you safe and hopefully reduce the risk of developing cancer for those that have had an infection," Cohen added.