What if part of cancer prevention has less to do with what you eat and more to do with infections you can prevent, detect, or treat?
A new analysis from the International Agency for Research on Cancer (IARC) estimates that 2.3 million new cancer cases worldwide in 2024 were attributable to infections, representing about 12% of all new cancer cases. That is roughly one in eight.
Three names help explain why: HPV, H. pylori, and hepatitis viruses.
The numbers are striking, but the more important part of the research is what comes next. Some of these infection-related cancers are potentially preventable through vaccination, screening, or treatment.
Gary Clifford, a senior author of the analysis and cancer epidemiologist at IARC, notes, “These are very actionable risk factors. We can test for them. We can vaccinate against them.”
HPV accounted for nearly 750,000 cancer cases
Human papillomavirus, or HPV, was responsible for an estimated nearly 750,000 cancer cases worldwide in 2024, according to the IARC analysis.
Cervical cancer is the best-known example, but HPV-related cancers are not limited to women.
The researchers estimated that HPV was associated with about 58,000 cancers of the oropharynx, tonsils, and base of the tongue, with roughly 47,000 of those cases occurring in males.
That makes HPV vaccination part of a broader cancer-prevention strategy rather than simply a cervical cancer issue.
The evidence for prevention is becoming increasingly concrete. A Swedish study published in The BMJ in 2026 found that women vaccinated against HPV before age 17 had approximately 80% lower invasive cervical cancer incidence than unvaccinated women. The association remained evident 13 to 15 years after vaccination.
Because that study was observational, it is important to say vaccination was associated with lower cancer incidence rather than claiming the study itself proved causation.
H. pylori is linked to hundreds of thousands of cancers
Then there is Helicobacter pylori, a bacterium that can persist in the stomach.
IARC estimated that H. pylori was responsible for roughly 760,000 cancer cases worldwide in 2024, making it the largest infectious contributor in the analysis. Most were gastric cancers.
The connection becomes particularly striking with non-cardia gastric cancer. Earlier IARC estimates found that H. pylori accounted for a very large share of these cancers, and the newer analysis continues to identify the bacterium as a major global cancer driver.
There is also evidence that treating the infection can lower subsequent cancer risk.
A 2025 systematic review and meta-analysis of eight randomized controlled trials found that eradicating H. pylori in otherwise healthy infected people was associated with a relative risk of 0.64 for gastric cancer, or about a 36% lower relative risk.
That does not mean treatment eliminates stomach-cancer risk. It does show why researchers are interested in identifying and treating H. pylori rather than viewing it simply as a stomach infection.
Hepatitis B and C add another major piece
Hepatitis B and hepatitis C are different viruses, but both are strongly connected to liver cancer.
The new analysis estimated that hepatitis B was responsible for approximately 360,000 cancer cases worldwide, while hepatitis C accounted for about 160,000. Most of those cases involved hepatocellular carcinoma, the most common form of primary liver cancer.
The prevention strategies are not identical.
There is a vaccine for hepatitis B, while hepatitis C has no vaccine. For hepatitis C, prevention depends on avoiding transmission and identifying and treating infections.
That distinction matters because “preventing infection-related cancer” is not one single intervention. Depending on the infection, it can mean vaccination, screening, antiviral treatment, or eradication therapy.
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The U.S. numbers are much smaller than the global total
The global figure should not be applied directly to American cancer statistics.
A 2024 American Cancer Society analysis estimated that 60,310 cancer cases among U.S. adults age 30 and older in 2019, or about 3.4% of cancers in that population, were attributable to seven infections. Those included HPV, H. pylori, hepatitis B and C, Epstein-Barr virus, Kaposi sarcoma-associated herpesvirus, and HIV.
The difference reflects the populations and methods used. The IARC analysis covers cancer worldwide in 2024, while the ACS analysis examined U.S. adults age 30 and older using 2019 data.
Earlier global research also found a substantial infection-related cancer burden. An IARC analysis published in 2019 estimated 2.2 million infection-attributable cancer cases in 2018, representing about 13% of cancers worldwide.
So the new analysis is not discovering that infections and cancer are connected for the first time. It’s updating and expanding the picture.
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The burden is heaviest in some parts of the world
The numbers also reveal a major geographic divide.
The researchers estimated that low- and middle-income countries accounted for 77% of infection-attributable cancer cases. In some parts of Asia and sub-Saharan Africa, infections account for more than one-quarter of all cancers.
Harriet Rumgay, an IARC scientist and co-author of the study, said the burden falls disproportionately on low- and middle-income countries and that the findings underscore the role infection control can play in reducing cancer worldwide.
That makes access part of the cancer-prevention story.
A vaccine that exists but does not reach the people who need it cannot prevent the cancers it was designed to prevent. The same applies to infection testing and treatment.
Prevention is the part researchers want to change
The most encouraging aspect of the findings may be that several of the infections involved already have established prevention tools.
HPV and hepatitis B can be targeted through vaccination. H. pylori can be detected and treated. Hepatitis C can be diagnosed and treated with antiviral medication.
And researchers are still looking for new tools.
Clifford has pointed specifically to Epstein-Barr virus, which was associated with about 260,000 cancer cases worldwide in 2024 and does not currently have an approved vaccine. He has argued that developing prevention tools for infections without vaccines could have a major impact.
That puts the new numbers in a different light.
The headline may be that one in eight cancers worldwide was linked to infections. But the more consequential question is how many of those cancers could be prevented if existing vaccines, screening, and treatments reached more people.
As Clifford told reporters, “Prevention works.”
The challenge is making sure people have access to it.
Were you surprised that infections such as HPV, H. pylori, and hepatitis account for such a large share of cancer worldwide?
