Roughly 1 in 8 cancer cases worldwide in 2024, translating to an estimated 2.3 million diagnoses, were caused by viral, bacterial, and parasitic infections, according to a global analysis published in The Lancet Oncology by researchers from the International Agency for Research on Cancer.
A worldwide incidence analysis released by the World Health Organization’s International Agency for Research on Cancer demonstrates that microbes play a far larger role in global oncology than many realize. The study evaluated 12 pathogens classified as Group 1 carcinogens, mapping how infections drive abnormal cell growth through chronic inflammation, tissue damage, and direct genetic alterations.
Infections Drive Millions of Global Cancers
Out of the 2.3 million new cases recorded in 2024, five specific infectious agents drove the vast majority of the burden. At the top of the list is the stomach bacterium Helicobacter pylori, which was linked to approximately 760,000 cases globally, primarily manifesting as gastric cancers concentrated heavily in eastern Asia.
Following closely behind was human papillomavirus, which accounted for roughly 750,000 cases, dominated by cervical cancer as well as anal, vulvar, vaginal, penile, and certain head and neck malignancies. The remaining top drivers include the liver-attacking hepatitis B virus at 360,000 cases, the Epstein-Barr virus at 260,000 cases—primarily driving nasopharyngeal cancer, certain gastric cancers, and Hodgkin lymphoma—and hepatitis C virus, which contributed around 160,000 cases primarily linked to hepatocellular carcinoma. Additional agents evaluated in the analysis included HIV, Kaposi sarcoma-associated herpesvirus, Schistosoma haematobium, human T-cell lymphotropic virus type 1, liver parasites common in Southeast Asia, and Merkel cell polyomavirus.
Nations Face Unequal Infection-Driven Burdens
Eastern Asia accounted for 42 percent of all infection-attributable cancers in 2024, largely driven by high rates of H. pylori and hepatitis B, while sub-Saharan Africa was responsible for 25 percent of cases, where HPV acts as the primary driver. Low- and middle-income countries bore roughly three-quarters of the global infection-driven cancer burden.
Public health experts point out that while highly effective vaccines exist for HPV and hepatitis B, and straightforward screening and antibiotic treatments exist for H. pylori, financial, political, and health-system barriers leave these interventions underused in poorer regions.
“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.”
Dr. Harriet Rumgay, scientist in the Cancer Surveillance Branch at IARC
Screening Programs Target Stomach Cancer
Countries like Japan, South Korea, and China have established population-based endoscopic screening programs to address high H. pylori prevalence.
Medical Professionals Assess Patient Risk
Medical professionals emphasize that most cancers are not caused by infection. In everyday clinical practice, healthcare providers examine multiple factors when assessing patient risk.
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