Nearly 1 in 8 Cancer Cases Worldwide Are Caused by Infections, Study Finds

Global Breakdown of Carcinogenic Infections

At the forefront of the findings are the bacterium Helicobacter pylori and human papillomavirus (HPV). Together, these two agents accounted for roughly 1.5 million cancer cases worldwide in 2024. H. pylori stands as the primary global driver of gastric cancers, while certain strains of HPV are responsible for virtually all cervical cancers alongside several other tumor types. Following these two leaders, hepatitis B virus (HBV) accounted for an estimated 360,000 cancer cases, and hepatitis C virus (HCV) contributed roughly 160,000 cases. In what lead author Harriet Rumgay, PhD, of IARC’s Cancer Surveillance Branch in Lyon, France, described as a striking finding, the Epstein-Barr virus (EBV) emerged as the fourth-leading infectious cause of cancer worldwide, accounting for roughly 260,000 diagnoses in 2024 and surpassing hepatitis C. The shift is largely attributed to mounting evidence that EBV plays a causal role in gastric cancer, complementing its established links to nasopharyngeal cancer and specific types of lymphoma. The updated IARC assessment also incorporated 16 additional infection-cancer links compared to the agency’s previous 2018 estimates, adding cancers caused by HIV and Merkel cell polyomavirus, as well as an expanded list of sites linked to HBV, HCV, Kaposi sarcoma-associated herpesvirus, and EBV. Gary Clifford, a cancer epidemiologist and study co-author based in Lyon, noted that scientific understanding has advanced significantly with the identification of new cancer-causing agents and clearer evidence regarding the breadth of cancers known microbes can trigger.

Regional Disparities in Low- and Middle-Income Countries

The global burden of infection-related cancers is not distributed evenly. Low- and middle-income countries account for more than three-quarters of all such cases, with Eastern Asia, sub-Saharan Africa, and Southeastern Asia bearing the heaviest load. Eastern Asia alone accounts for 42% of all infection-attributable cancers, driven predominantly by gastric cancers linked to H. pylori and liver cancers caused by hepatitis B. Meanwhile, high rates in sub-Saharan Africa are driven by HPV and Kaposi sarcoma-associated herpesvirus, a situation compounded by HIV, which increases the risk of cancers triggered by other carcinogenic infections. By contrast, North America and Europe see a much lower overall burden, where HPV and H. pylori remain the primary sources of infection-linked malignancies.

Public Health Implications and Prevention Tools

The study highlights the urgent need to scale up proven interventions, such as vaccinations against HPV and hepatitis B, alongside testing and treatment for HIV, hepatitis B, C, and H. pylori. Nina R. Salama, PhD, of the Fred Hutchinson Cancer Center in Seattle, who studies H. pylori but was not involved in the new research, noted that the data remind physicians of the mortality caused by infections that they have clinical tools to address in many instances. Salama emphasized that because infection-related cancers offer multiple intervention points, continued work is warranted on both biological research for improved treatments and vaccine development for agents that currently lack vaccines, alongside better implementation science to deliver existing defenses. IARC researchers also highlighted that investment in new prevention tools, including vaccines targeting Epstein-Barr virus, should remain a high priority.