An estimated 2.3 million new cancer cases worldwide in 2024—about 12%, or one in eight—were attributable to infections, according to an IARC-led analysis published online in The Lancet Oncology on 28 September 2026. The figure is a population-level estimate, not a count of tumors individually proven to have been caused by an infection.
What does “attributable to infection” mean?
The researchers used cancer-incidence data from GLOBOCAN 2024 to estimate population-attributable fractions: the share of cases that would not have occurred in the absence of the studied infectious exposure, under the analysis’s assumptions. This method estimates a preventable burden across populations; it cannot establish what caused a particular person’s cancer or predict whether an infected individual will develop cancer.
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The estimate covers 2024 diagnoses. IARC’s separate GLOBOCAN summary reports 20.6 million new cases across 34 cancer types in 186 countries that year. The study’s own estimate—2.3 million, or 12%—is the appropriate figure to quote rather than recalculating a share from rounded totals. IARC’s GLOBOCAN 2024 summary provides that broader context.
Which infections accounted for the largest estimated numbers?
The IARC-led study evaluated 12 infectious agents classified as carcinogenic to humans by the IARC Monographs Programme. Its largest estimated contributors were Helicobacter pylori and HPV, followed by hepatitis B virus and Epstein–Barr virus.
| Infectious agent | Estimated 2024 cases | Share of all cases |
|---|---|---|
| Helicobacter pylori (H. pylori) | 760,000 | 4% |
| Human papillomavirus (HPV) | 750,000 | 4% |
| Hepatitis B virus (HBV) | 360,000 | 2% |
| Epstein–Barr virus (EBV) | 260,000 | 1% |
| Hepatitis C virus (HCV) | 160,000 | Less than 1% |
Counts and percentages are the rounded estimates reported by the IARC-led study; its abstract identifies five major pathogens, and their rounded case counts sum to 2.29 million. The study’s scope also included Kaposi’s sarcoma-associated herpesvirus, Schistosoma haematobium, human T-cell lymphotropic virus, Opisthorchis viverrini, Clonorchis sinensis, Merkel cell polyomavirus and HIV. The expanded analysis included HIV and Merkel cell polyomavirus, newly established associations, and EBV-linked gastric cancer. The PubMed record for the study summarizes its methods and findings.
Where was the estimated burden highest?
Eastern Asia had the largest absolute number: an estimated 990,000 infection-attributable cases, or 42% of the global total. Its age-standardised incidence rate was 31.9 per 100,000. For comparison, the global age-standardised rate was 22.7 per 100,000; the rate was 28.5 in sub-Saharan Africa, 24.3 in central and eastern Europe, and 23.1 in southeastern Asia.
A case count and an age-standardised rate answer different questions. Counts show the estimated number of diagnoses; age-standardisation adjusts for differences in population age structure, making incidence comparisons less dependent on how young or old a region’s population is. Eastern Asia’s largest count does not by itself mean it had the highest rate.
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What prevention approaches did the study identify?
The authors point to existing measures that could prevent some infection-related cancers, while noting that implementation is often incomplete. Approaches named in the study include:
- Vaccination: HPV and HBV vaccination.
- Testing and treatment: HIV, H. pylori, HBV and HCV.
- Reducing transmission: safe injection practices, condoms and access to pre-exposure prophylaxis to prevent HIV transmission.
- Screening: detection of precancerous lesions for HPV-driven cervical and anal cancers.
- Further prevention development: the authors highlight the need for additional prevention tools, notably for EBV.
These are population-level prevention approaches, not personal medical instructions. Whether vaccination, testing, treatment or screening is appropriate depends on local public-health guidance and an individual’s clinical circumstances.
Independent reader supportYour contribution helps us test, update, and keep practical guides available for everyone.What the one-in-eight estimate does—and does not—say
The result shows that infections represent a substantial, partly preventable share of cancer incidence worldwide. It does not mean that one in eight people with cancer had a tumor individually traced to an infection, nor that infection inevitably leads to cancer. It is an estimate for populations based on the exposures and cancer data included in the analysis.
For the full methods, pathogen estimates and regional breakdown, see the study record in PubMed and IARC’s summary of the findings.
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