About 2.3 million of the cancers diagnosed worldwide in 2024, roughly one in eight, were caused by infections, according to a new analysis in The Lancet Oncology. Two microbes account for most of the total: the stomach bacterium Helicobacter pylori was tied to about 760,000 cases, and human papillomavirus (HPV) to about 750,000.
The paper, led by Harriet Rumgay of the International Agency for Research on Cancer with IARC’s Gary Clifford as senior author, was published on September 28. It counts only five pathogens, and every one of them is something medicine can already test for, vaccinate against or treat.
Five pathogens, one large total
The paper itself puts the top-line figure at 12 percent of all cancers diagnosed in 2024, or about 2.3 million new cases, and ScienceAlert’s summary of the paper repeats it. H. pylori accounts for 4 percent of all cancers and HPV for another 4 percent. Hepatitis B virus follows at 2 percent, Epstein-Barr virus at 1 percent, and hepatitis C virus at less than 1 percent.
In absolute terms, Newsweek’s account of the analysis lists roughly 760,000 cases for H. pylori, 750,000 for HPV, 360,000 for hepatitis B, 260,000 for Epstein-Barr virus and 160,000 for hepatitis C. Those five figures sum to about 2.29 million, which is where the 2.3 million total comes from. The cancers involved are mostly stomach cancer for H. pylori, cervical cancer for HPV, liver cancer for both hepatitis viruses and nasopharyngeal cancer for Epstein-Barr.
The ranking matters because the two leading causes are a bacterium and a virus, each with a clear route to prevention: antibiotics clear H. pylori, and a vaccine blocks HPV.
Where the burden falls
The geography is uneven. About 75 percent of infection-related cancers occurred in low-income and middle-income countries, and Eastern Asia alone accounted for 42 percent of the global total, driven mainly by H. pylori and hepatitis B, the ScienceAlert report says. Sub-Saharan Africa and southeastern Asia also carry a heavy load, and Newsweek adds Central and Eastern Europe to the regions with the highest infection-related burdens. The distribution follows where infections are common and where health services are thin, which is why the same five pathogens produce very different cancer patterns from one region to the next.
The authors write that “many carcinogenic infectious agents have existing or potential preventive interventions, including vaccines, diagnostics, treatments, and safe injection practices,” and that such strategies “are often underused due to societal, financial, and political barriers.” The gap, in other words, is mostly one of delivery. The tools exist, and the places with the most infection-driven cancer tend to be the places where vaccination, screening and treatment reach the fewest people.
What separates 2024 from earlier counts
IARC has run this exercise before. Its earlier analysis, published in The Lancet Global Health in December 2019, estimated 2.2 million infection-attributable cases in 2018, or 13 percent of new cancers worldwide, and named four main agents: HPV, H. pylori, hepatitis B and hepatitis C. The new paper puts the count slightly higher in absolute terms at 2.3 million but slightly lower as a share, at 12 percent, and adds Epstein-Barr virus to the group of five.
Global cancer cases have grown, so infection-related cancers are falling as a fraction of the whole while remaining enormous in raw numbers. Vaccination and treatment have not yet bent the curve enough to shrink the count itself, and the newest estimate still spans more than 20 types of cancer, among them cervical, stomach, liver and lymphatic disease, according to reporting on the analysis.
Testing, vaccinating, treating
Clifford framed the findings as a to-do list rather than a warning. In Scientific American’s coverage, he calls these “very actionable risk factors” that health systems can test for and vaccinate against. The prevention menu named there includes hepatitis B vaccination, screening and treatment for hepatitis C, antibiotics for H. pylori, and the HPV vaccine, which protects against six cancer types.
Newsweek quotes Clifford as saying the findings “demonstrate that a large fraction of cancers are caused by known infectious causes, and are thus preventable.” Nancy Lee of Memorial Sloan Kettering Cancer Center, quoted in the Scientific American piece, said, “HPV vaccination is critical to preventing infection and reducing the burden of HPV-related cancers.”
Speed is now the unresolved part. The 2018 and 2024 estimates are separated by six years in which the number barely moved, and the authors point to financial and political barriers rather than missing technology. Whether the next IARC count, covering a later year, shows a figure below 2.3 million will depend on how much of the vaccination, screening and treatment already available is actually delivered.
This article was produced with the assistance of AI and reviewed by Morning Overview editors prior to publication.
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