About 2.3 million cancer diagnoses in 2024, or 12% of all cases globally, were caused by infections, according to a new study from the Interna ti onal Agency for Research on Cancer (IARC).

Those cancers were attributable to 12 infectious agents known to be carcinogenic to humans. At the top of list were Helicobacter pylori and human papillomavirus (HPV), which together caused roughly 1.5 million cancers worldwide in 2024. H. pylori is the primary cause of gastric cancers globally, while certain strains of HPV cause virtually all cervical cancers and contribute to several other cancer types.

Meanwhile, an estimated 360,000 cancer cases were attributed to hepatitis B virus and 160,000 to hepatitis C. And in what researchers called a notable finding, Epstein-Barr virus (EBV) accounted for roughly 260,000 cancer diagnoses in 2024.

Experts said the results, published in Lancet Oncology, highlight the many cancer cases that are potentially preventable through vaccinations and infectious disease screening and treatment.

“Hopefully these data can help remind physicians that [infection-related] cancers are an important cause of mortality that they have tools to address in some, but not all, cases,” said Nina R. Salama, PhD, of Fred Hutchinson Cancer Center in Seattle, who studies H. pylori but was not involved in the new work.

The analysis, according to IARC, is the most up-to-date worldwide assessment of cancers attributable to infections. It used data for 2024 from the agency’s online GLOBOCAN database, which provides global statistics on 36 types of cancer.

Compared with IARC’s previous estimates, from 2018, the update incorporated 16 additional infection-cancer links, said lead author Harriet Rumgay, PhD, of IARC’s Cancer Surveillance Branch in Lyon, France.

The additions included cancers caused by HIV and Merkel cell polyomavirus, as well as an expanded list of cancer sites linked to hepatitis B and C, Kaposi sarcoma-associated herpesvirus, and EBV.

EBV emerged as the fourth-leading infectious cause of cancer worldwide in 2024, ahead of hepatitis C, which Rumgay called “one of the most striking findings.” The shift was largely due to growing evidence that EBV plays a causal role in gastric cancer in addition to its known links to nasopharyngeal cancer and some types of lymphoma. 

The global burden of infection-related cancers was not shared evenly. Low- and middle-income countries — particularly in Eastern Asia, sub-Saharan Africa, and Southeastern Asia — accounted for more than three-quarters of all cases. An estimated 42% of all infec tion-att ributable cancers occurred in Eastern Asia, driven largely by gastric cancers caused by H. pylori and liver cancers due to hepatitis B.

The burden was also high in sub-Saharan Africa, driven by HPV and Kaposi sarcoma-associated herpesvirus — and made worse by HIV, which increases the risk of cancers caused by other carcinogenic infections.

In North America and Europe, HPV and H. pylori were the main causes of infection-attributable cancers. 

According to the IARC team, the findings reinforce the need to “scale up proven interventions,” including vaccinations against HPV and hepatitis B and testing and treatment for HIV, hepatitis B and C, and H. pylori.

Investment in new prevention tools, including EBV vaccines, should also be a priority, the researchers said.

Salama agreed on both points. “Since [infection-related] cancers have many possible points of intervention,” she said, “it really motivates continued work on both the biology to elucidate better treatments and new vaccine approaches for the agents that don’t have vaccines — as well as more implementation science to deliver the vaccines and treatments we do have.”

The study received no external funding. Rumgay and Salama had no relevant disclosures.