IARC analysis: about 1 in 8 new cancers in 2024 linked to infections

A new IARC analysis finds that around one-eighth of all new cancer cases worldwide in 2024 — roughly 2.3 million cases — are linked to infectious agents. The report catalogs infectious causes that have established causal links to cancer and highlights prevention approaches that can reduce this burden.

The analysis identifies 12 infectious agents with established relationships to human cancers. The list in the report includes Helicobacter pylori, human papillomaviruses (HPV), hepatitis B virus (HBV), hepatitis C virus (HCV), Epstein-Barr virus (EBV), the virus associated with Kaposi sarcoma, schistosoma infection of the bladder, HTLV-1, two liver flukes (Opisthorchis viverrini and Clonorchis sinensis), Merkel cell polyomavirus (MCV), and HIV.

The IARC authors emphasize that the cancer burden tied to infections is not evenly distributed. Higher proportions of these cancers occur in populations of low- and middle-income countries. The report notes ongoing gaps in access to prevention tools such as vaccination, screening, and treatments that reduce infection prevalence.

The report and accompanying commentary point to three practical prevention levers:

• Vaccination: Vaccines exist for some causal agents (for example, vaccines targeting HPV and HBV) and can prevent the infections that later lead to cancer.
• Treatment of infections: Antiviral or antimicrobial therapy to clear infections (noted for agents like H. pylori, HBV, HCV) can lower cancer risk over time.
• Screening: Organized screening programs can detect precancerous changes or early cancers caused by infectious agents, enabling earlier intervention.

Why the estimate may be conservative

IARC researchers acknowledge limitations in the analysis. Their approach uses population-level estimates rather than following individual patients over time, so results depend heavily on the quality of cancer and infection data available in each country. The study also restricted its scope to infectious agents already proven to cause cancer. That means additional infections with causal roles yet to be fully demonstrated would not be counted, potentially underestimating the total impact.

Research and public-health implications

IARC's analysis reinforces the potential for public-health measures to reduce cancer incidence by preventing or treating infections. Expanding vaccination coverage, improving access to diagnostic testing and treatment, and implementing targeted screening programs are practical steps cited by the study as able to lower the infection-related cancer burden, particularly in countries where those cancers are concentrated.

The analysis used 2024 cancer data and was carried out in France. Its results were published in The Lancet Oncology on September 28, 2026. The authors call for continued efforts to strengthen surveillance and prevention programs and note the need to improve data quality to refine future estimates.