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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. This 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 how many cancer cases were attributable to 12 infectious agents classified as carcinogenic to humans by the International Agency for Research on Cancer (IARC). A population-attributable estimate models how many cases would not have occurred in the absence of the exposure, under the analysis’s assumptions. It does not establish the cause of any individual person’s cancer or mean that infection inevitably leads to cancer.
The study’s estimate is 2.3 million cases, or 12% of new cancer diagnoses worldwide in 2024. IARC’s separate GLOBOCAN summary reports 20.6 million new cases across 34 cancer types in 186 countries that year; the 12% figure is the study’s own rounded estimate, not a recalculation from those rounded totals. The study record and abstract are available through PubMed.
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Helicobacter pylori and human papillomavirus (HPV) were the largest estimated contributors. The study’s rounded figures for its five leading pathogens are:
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| Infectious agent | Estimated attributable cases worldwide in 2024 | Share of all cases |
|---|---|---|
| Helicobacter 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% |
These are estimates from the IARC-led analysis, published in 2026. The case counts and percentages are rounded, so adding the rows does not produce an exact total.
Which infectious agents did the study include?
In addition to the five leading contributors, the analysis covered Kaposi’s sarcoma-associated herpesvirus, Schistosoma haematobium, human T-cell lymphotropic virus, Opisthorchis viverrini, Clonorchis sinensis, Merkel cell polyomavirus, and HIV. The expanded scope includes HIV, Merkel cell polyomavirus, newly established associations, and EBV-linked gastric cancer, as described by IARC.
Rank #2
The analysis grouped estimates by sex, country, and age, then aggregated them by United Nations subregion and World Bank income group. Its findings describe the burden associated with the included agents at population scale; they are not a ranking of an individual’s personal cancer risk.
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Eastern Asia had the largest absolute number: an estimated 990,000 infection-attributable cases, or 42% of the global total. That is a case count, not an age-adjusted comparison. The study’s age-standardised incidence rates, per 100,000 people, were:
| Area | Age-standardised rate |
|---|---|
| Eastern Asia | 31.9 per 100,000 |
| Sub-Saharan Africa | 28.5 per 100,000 |
| Central and eastern Europe | 24.3 per 100,000 |
| Southeastern Asia | 23.1 per 100,000 |
| Worldwide | 22.7 per 100,000 |
Age standardisation makes rates more comparable by accounting for differences in the age structures of populations. It answers a different question from the raw number of cases, which is also shaped by population size.
Independent reader supportYour contribution helps us test, update, and keep practical guides available for everyone.What prevention approaches did the authors identify?
The study authors point to measures that are scientifically supported but often underused. These include:
- Vaccination against HPV and HBV.
- Testing and treatment for HIV, H. pylori, HBV, and HCV.
- Safe injection practices, and access to condoms and pre-exposure prophylaxis to help prevent HIV transmission.
- Screening for precancerous lesions associated with HPV-driven cervical and anal cancers.
The authors also note the need to develop further prevention tools, particularly for EBV. Whether a person should receive a vaccine, test, treatment, or screening depends on local public-health guidance and individual clinical circumstances; the global estimate does not predict an individual’s outcome. IARC’s report of the analysis is at iarc.who.int/news-events, and its GLOBOCAN 2024 summary is at gco.iarc.who.int.
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