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Five infections linked to 1 in 8 cancers worldwide, new global study finds
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In brief
An estimated 2.3 million new cancer cases in 2024—about 12% of all cancers diagnosed worldwide—were caused by infections, according to a study from the International Agency for Research on Cancer (IARC) published in The Lancet Oncology. Five pathogens accounted for most of this burden: H. pylori, HPV, hepatitis B, Epstein-Barr virus and hepatitis C. Most of these cancers are preventable through vaccination, screening or treatment of the underlying infection.
Infections are the second-largest preventable cause of cancer after tobacco, according to the International Agency for Research on Cancer (IARC), the World Health Organization's cancer research body. A study led by IARC researcher Harriet Rumgay and colleagues, published in The Lancet Oncology on 28 September 2026, estimated that 2.3 million of the roughly 20 million new cancer cases recorded worldwide in 2024 were attributable to infectious agents.
The researchers used data from the Global Cancer Observatory's GLOBOCAN database to calculate how many cancer cases in 2024 could be traced to each of several infectious agents classified by IARC as Group 1 human carcinogens. Five pathogens accounted for the overwhelming majority of infection-linked cancers.
The five leading infections
Helicobacter pylori, a stomach bacterium, topped the list with about 760,000 cancer cases, equal to 4% of all new cancers worldwide that year. According to the study, 85% of H. pylori-attributable cancers were non-cardia gastric cancer, a stomach cancer subtype.
Human papillomavirus (HPV) was linked to roughly 750,000 cases, also about 4% of the global total. The health-news outlet News-Medical.net, which reviewed the study, reported that HPV-related cancers were overwhelmingly cervical cancer, but also included anal, vulvar, vaginal and penile cancers as well as some head and neck cancers.
Hepatitis B virus (HBV) accounted for about 360,000 cases, a 2% population-attributable fraction, mostly liver cancer (hepatocellular carcinoma). Epstein-Barr virus (EBV) was tied to around 260,000 cases, primarily nasopharyngeal cancer, and the study newly linked EBV to some stomach cancers as well, according to IARC. Hepatitis C virus (HCV) caused an estimated 160,000 cases, also mainly liver cancer.
IARC noted that its wider analysis also covered other carcinogenic infections, including HIV and Merkel cell polyomavirus, though these contributed far fewer cases than the top five.
| Infection | Estimated cases | Share of all cancers | Main cancer type |
|---|---|---|---|
| H. pylori | 760,000 | 4% | Non-cardia gastric (stomach) cancer |
| HPV | 750,000 | 4% | Cervical cancer, plus anal, vulvar, vaginal, penile and some head-and-neck cancers |
| Hepatitis B | 360,000 | 2% | Liver cancer (hepatocellular carcinoma) |
| Epstein-Barr virus | 260,000 | 1% | Nasopharyngeal cancer; some gastric cancers |
| Hepatitis C | 160,000 | under 1% | Liver cancer |
Why the burden is uneven across the world
The study found that 77% of infection-attributable cancer cases occurred in low- and middle-income countries. Eastern Asia carried the largest absolute burden, with about 990,000 cases—42% of the global total—driven largely by H. pylori and hepatitis B. In sub-Saharan Africa, infections caused roughly one in four new cancer cases, a share strongly influenced by HPV and HIV-related cancers, according to the vaccine advocacy group Gavi, which reported on the findings. By contrast, a separate Swiss public broadcaster SRF report on the same research noted that infections cause only about 5% of cancers in Western Europe, illustrating the gap between regions.
Most of these cancers are preventable
IARC and outside reviewers of the study stressed that infection-driven cancers are among the most preventable. Hepatitis B vaccination is described as 98–100% effective at preventing the infection that can lead to liver cancer, and HPV vaccines are already licensed and used in national immunization programs in many countries. Hepatitis C has no vaccine yet, but antiviral drugs cure more than 95% of infections, removing the long-term cancer risk. H. pylori infection can be detected and cleared with antibiotic treatment, while vaccine candidates against it remain in development.
For HPV- and H. pylori-related cancers that have already progressed, screening programs—cervical cytology or HPV testing for cervical cancer, and endoscopy or stool antigen tests for H. pylori-linked stomach disease—allow earlier detection and treatment.
Infection-related cancers remain a major global challenge, with the burden falling disproportionately on populations in low- and middle-income countries.
What this means for individual risk
The five infections do not guarantee cancer in every person who carries them; the study's percentages describe population-level attributable fractions, not individual odds. Chronic, long-term infection—left undiagnosed or untreated over years—is what raises cancer risk, which is why IARC and the researchers behind the study point to vaccination, testing and timely treatment as the main tools to reduce the global cancer burden linked to these pathogens.
Questions
- Which infection causes the most cancer cases worldwide?
- Helicobacter pylori causes the most, an estimated 760,000 cancer cases in 2024 (4% of all new cancers), mostly non-cardia gastric cancer, according to the IARC-led study published in The Lancet Oncology.
- What percentage of all cancers worldwide are linked to infections?
- About 12%, or roughly 2.3 million of the estimated 20 million new cancer cases recorded in 2024, according to the IARC study.
- Can HPV- and hepatitis B-related cancers be prevented?
- Yes. HPV vaccines and hepatitis B vaccines are already in use worldwide; hepatitis B vaccination is reported to be 98-100% effective, and HPV vaccination plus cervical screening can prevent most cervical cancers.
- Is hepatitis C-related liver cancer preventable?
- There is no hepatitis C vaccine yet, but antiviral medicines cure more than 95% of hepatitis C infections, which removes the long-term liver cancer risk tied to chronic infection, according to the News-Medical.net review of the study.
- Why is the infection-related cancer burden higher in some regions?
- The study found 77% of infection-linked cancer cases occur in low- and middle-income countries, with Eastern Asia and sub-Saharan Africa carrying the heaviest burden, compared with about 5% of cancers in Western Europe, according to IARC and SRF's reporting on the research.
How the world is telling it
- GermanSwiss (SRF) and German coverage frames the findings around the same IARC/Lancet Oncology study, emphasizing that roughly one in eight cancers worldwide traces back to infection and highlighting the sharp contrast between low infection-related cancer rates in Western Europe (about 5%) and much higher rates in sub-Saharan Africa and East Asia.
Sources
- IARC — Global burden of cancer attributable to infections in 2024: One in eight cancers worldwide linked to infections
- News-Medical.net — Infections caused 1 in 8 cancer cases worldwide in 2024, study finds
- Gavi — Meet the five infections responsible for almost one in eight cancers worldwide
- SRF — Erkenntnis der Krebsforschung: Am Anfang jeder achten Krebserkrankung steht eine Entzündung
This piece was prepared with artificial intelligence and passed an automated source check before publication. If you see an error, ask for a correction. Request a correction or reply · How we make this
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