What's trending, explained.
What's trending, explained.
The World Health Organization's cancer research agency has released what it calls the most complete picture yet of how infections cause cancer — and the number is startling. The International Agency for Research on Cancer (IARC) estimates that about 2.3 million new cancer cases worldwide in 2024, roughly 12 percent of the global total — one in eight — were caused by infections.
The study, published in *The Lancet Oncology* in late September 2026 and reported widely this week, analyzed 12 infectious agents that IARC classifies as definite causes of cancer in humans, using data from the agency's Global Cancer Observatory. Five pathogens account for the vast majority of the total: the stomach bacterium *Helicobacter pylori* (about 760,000 cases), human papillomavirus or HPV (about 750,000), hepatitis B (about 360,000), the Epstein-Barr virus or EBV (about 260,000), and hepatitis C (about 160,000).
In percentage terms, *H. pylori* and HPV each account for roughly 4 percent of all new cancer diagnoses worldwide, hepatitis B for about 2 percent, EBV for about 1 percent, and hepatitis C for less than 1 percent. All cervical cancer — around 600,000 cases — is attributed to HPV. Hepatitis B is linked to about half of hepatocellular carcinoma, the most common liver cancer, and hepatitis C to a fifth. EBV is linked to 88 percent of nasopharyngeal cancer, a cancer of the upper throat.
The finding reframes where cancer prevention can actually work. Cancer is usually discussed in terms of aging, genetics, tobacco, and alcohol — factors that are hard to change at a population level. Infections are different: many of the tools to fight them already exist and are cheap. HPV and hepatitis B vaccines are among the most effective cancer-prevention interventions ever developed, hepatitis C can be cured with a short course of antivirals, and *H. pylori* can be found with testing and treated with antibiotics.
That makes the geography of the problem the real scandal. More than three quarters of infection-linked cancers occur in low- and middle-income countries: East Asia accounts for about 42 percent of them, sub-Saharan Africa about 28.5 percent, and Southeast Asia carries a larger share than the world average — 16 percent of its cancers are infection-linked versus 12 percent globally. Researchers point to vaccine hesitancy, cuts to development aid, and weak health systems as reasons proven prevention programs still fail to reach the people who need them most.
The study also expands the map of infection-linked cancer. It adds infectious agents that earlier estimates left out, such as HIV and the Merkel cell polyomavirus, and incorporates newer findings — including recent evidence linking EBV with stomach cancer. The mechanisms are now fairly well understood: some pathogens damage cells through chronic inflammation that produces mutations over time; others insert their own DNA into human cells or disable the proteins that stop cells from dividing out of control.
One important caveat: a population-level link is not an individual prediction. Getting an infection does not mean you will develop cancer — these are slow processes that unfold over many years, and only a fraction of infected people ever develop the associated disease. The study's numbers describe what could be prevented across populations, not what will happen to any one person. As always with health news, questions about your own risk are for your doctor, not a headline.
The study is, at its core, an argument for spending. IARC and WHO researchers say many of these cancers could be prevented by scaling up measures that are already proven: HPV and hepatitis B vaccination, testing and treatment for *H. pylori* and viral hepatitis, and wider access to prevention basics. They also identify a research priority: new prevention tools, such as a vaccine against EBV, which currently does not exist.
Whether that argument lands will depend on funding decisions in the coming years — an uncertain prospect given the current pressure on development aid budgets. Watch for national vaccination policy changes, expanded screening programs in high-burden regions, and whether the stark regional imbalances in the data push global health funders to treat infection control as cancer policy. The headline number is 2.3 million. The policy question is how many of next year's 2.3 million could simply never happen.