New study reveals surprising factor behind 1 in 8 worldwide cancer cases

LYON, France - A new study reveals that an estimated 2.3 million new cancer cases worldwide in 2024 – about 12% of all new cancer cases – were caused by infections. 

The analysis from the International Agency for Research on Cancer (IARC) is based on cancer burden estimates from the IARC Global Cancer Observatory database.

Study’s findings

Big picture view:

Published on Sept. 28 in The Lancet Oncology, the researchers estimated new cancer cases attributable to 12 infectious agents known to cause cancer in humans, including viruses, a bacterium and parasites.

These 12 agents were: Helicobacter pylori, human papillomavirus (HPV), hepatitis B virus (HBV), hepatitis C virus (HCV), EBV, Kaposi sarcoma-associated herpesvirus (KSHV), Schistosoma haematobium, human T-cell lymphotropic virus type 1 (HTLV-1), Opisthorchis viverrini, Clonorchis sinensis, Merkel cell polyomavirus, and HIV. 

The greatest cancer burden was linked to H. pylori, which was responsible for an estimated 760,000 cancer cases in 2024, closely followed by HPV, with 750,000 cases. 

In addition, HBV accounted for about 360,000 cases, EBV for approximately 260,000 cases, and HCV for about 160,000 cases. Together, the five infectious agents accounted for almost all cancers caused by infections.

What they're saying:

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

Geographical inequalities

Dig deeper:

The study also revealed geographical inequalities. 

Eastern Asia accounted for 42% of all infection-attributable cancers worldwide, largely driven by H. pylori and HBV. 

The burden was also particularly high in Sub-Saharan Africa, driven by HPV and KSHV and worsened by HIV. 

More than three-quarters of infection-related cancers occurred in low- and middle-income countries, where access to prevention and treatment remains unequal, the agency noted.

Analysis shows infection-related cancers continue to evolve

Why you should care:

EBV is the fourth largest infectious cause of cancer globally, ahead of HCV. This reflects growing evidence that EBV contributes not only to nasopharyngeal cancer and lymphomas but also to a proportion of gastric cancers. 

"This updated analysis shows that the landscape of infection-related cancers continues to evolve as scientific evidence advances," said Dr. Gary Clifford, a senior co-author of the study. "It also highlights where future investments in new prevention tools could have the greatest impact, particularly for infections such as EBV, for which effective vaccines are not yet available." 

IARC said most infection-related cancers can already be prevented through well-established public health measures, including vaccination against HPV and HBV, testing and treatment for H. pylori and viral hepatitis, HIV prevention and care, and screening programmes for HPV-related cancers. However, the agency said these interventions remain underused in many parts of the world because of persistent financial, political and health-system barriers. 

Study limitations 

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.

Despite the findings, Dr. Joshua Cohen, medical director of the Gynecologic Cancer Program of City of Hope Orange County in Irvine, California, told Fox News Digital that "most cancers are not caused by infection."

"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," Cohen said.

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

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.

"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.