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In the latest broad global estimate, infections accounted for 10.2% of new cancer cases in 2022, according to a WHO/IARC analysis published in 2026. A widely cited earlier estimate found 2.2 million cases, or about 13% of new cancers, in 2018. These estimates refer to different years and study frameworks, so the gap between them should not be read as proof that infection-related cancer has declined.
What the global estimates say
The newer figure is a share: infections were attributed with 10.2% of new cancers in 2022 in a 2026 peer-reviewed analysis of 30 modifiable risk factors across 185 countries and 36 cancer sites. WHO summarizes the result as approximately 10% of cancers diagnosed globally in 2022.
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The earlier IARC estimate was a count and a share: about 2.2 million new cancer cases worldwide, or 13% of all new cases, in 2018. That analysis also reported an age-standardized incidence rate of 25.0 cases per 100,000 person-years. The count is an estimate, not a tally of individually proven cases.
Because the studies use different reference years and estimation frameworks, comparing 13% with 10.2% does not establish a trend. A sound comparison would also need to account for the agents and cancer sites included, exposure and latency assumptions, the denominator, and geographic aggregation.
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Which infections contributed most in the 2018 estimate?
IARC’s 2018 breakdown attributed the largest numbers of new cases to Helicobacter pylori (H. pylori) and human papillomavirus (HPV), followed by hepatitis B and C. Counts below are rounded estimates; their sum is approximately 2.23 million, so the overall result is best reported as about 2.2 million.
| Infection category | Estimated new cases attributable to it worldwide in 2018 | Important cancer association |
|---|---|---|
| H. pylori | 810,000 | Stomach cancer |
| HPV | 690,000 | Cervical cancer |
| Hepatitis B virus | 360,000 | Liver cancer |
| Hepatitis C virus | 160,000 | Liver cancer |
| Other infectious agents | 210,000 | Includes agents such as Epstein–Barr virus and human herpesvirus 8; the category is not fully captured |
These are estimates of cancers attributable to each agent in the 2018 analysis, not the number of people infected with it. WHO also identifies Epstein–Barr virus among carcinogenic infections; the five infections it highlights are examples, not an exhaustive list of oncogenic agents.
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Why the burden varies by region
The 2018 IARC analysis found the highest infection-attributable age-standardized incidence rates in Eastern Asia (37.9 per 100,000 person-years) and sub-Saharan Africa (33.1). The lowest reported rates were in Northern Europe (13.6) and Western Asia (13.8). China accounted for about one-third of infection-attributable cases in that analysis, driven particularly by H. pylori and hepatitis B.
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These figures describe the 2018 analysis, not a current country ranking. Global percentages can conceal substantial differences in infection prevalence, cancer patterns, and the burden within particular populations.
What “caused by infection” means
Researchers estimate the share of cancers in a population that can be attributed to particular exposures using population-level methods. The 2026 study estimated population-attributable fractions, accounting for the time lag between exposure and cancer by using exposure prevalence data around 2012 for its 2022 cancer estimates. Such estimates describe burden across populations; they cannot determine what caused an individual person’s cancer.
An infection associated with cancer does not mean that everyone who acquires it will develop cancer. Nor does a population estimate show that a particular person’s tumor was caused by an infection. The 2018 analysis estimated cancers linked to infectious agents classified as carcinogenic by IARC; the 2026 infection estimate was part of a broader analysis of 30 modifiable risk factors, with adjustment for overlap among risks.
Independent reader supportYour contribution helps us test, update, and keep practical guides available for everyone.How infection-related cancers can be prevented
Some cancer risk from infections can be reduced. WHO identifies vaccination against HPV and hepatitis B for groups for whom vaccination is recommended, alongside public-health measures to prevent or treat carcinogenic infections. The appropriate vaccination, screening, or treatment advice depends on local guidance and an individual’s circumstances; these global burden figures are not personal medical advice.
The practical takeaway is that infections account for a substantial, partly preventable share of cancer worldwide. The most current estimate in the cited global analysis is about one in ten new cases in 2022; the often-quoted 2.2 million and 13% figures specifically describe 2018.
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