How Infections Linked to Cancer Became One in Eight Cases

A startling share of the world's cancers begins with something far smaller than a tumor: a germ. A sweeping new analysis estimates that about 2.3 million new cancer cases in 2024 — roughly one in eight diagnoses worldwide — trace back to just 12 infectious agents that scientists classify as carcinogenic. For anyone trying to understand infections linked to cancer, this is the most complete global accounting ever published, and it carries an uncomfortable message: a large share of these cases could have been prevented with tools that already exist.

The analysis comes from the International Agency for Research on Cancer, the World Health Organization's cancer research arm, and appeared in The Lancet Oncology in late September 2026. Its authors worked from 2024 figures in the agency's GLOBOCAN database, which compiles statistics on 36 cancer types from registries around the world. Compared with the agency's previous estimate in 2018, the update adds 16 newly recognized infection-cancer links — among them HIV and Merkel cell polyomavirus — according to lead author Harriet Rumgay of the agency's Cancer Surveillance Branch in Lyon, France, as reported by Medscape.

The five infections doing nearly all the damage

Just five pathogens account for almost the entire burden:

• Helicobacter pylori — a stomach bacterium tied to about 760,000 cases, mostly stomach cancer.
• Human papillomavirus (HPV) — linked to roughly 750,000 cases, and the cause of virtually all cervical cancer.
• Hepatitis B — an estimated 360,000 cases, concentrated in liver cancer.
• Epstein-Barr virus (EBV) — around 260,000 cases, including nasopharyngeal cancers and lymphomas.
• Hepatitis C — roughly 160,000 cases, again mostly in the liver.

The concentration is extreme. The top two germs on that list account for roughly one and a half million cases between them, and every cervical cancer case — about 600,000 a year — is attributed to HPV. EBV sits behind an estimated 88 percent of nasopharyngeal cancers, tumors of the upper throat, while hepatitis B is connected to about half of hepatocellular carcinoma, the most common form of liver cancer, according to health outlet RecaTools, which reviewed the findings.

The burden lands hardest where care is scarcest

More than three-quarters of these cancers struck people in low- and middle-income countries, where vaccination and screening programs are thinnest. East Asia carried the heaviest regional load — around 900,000 cases, about two in five of the global total — a reflection of how widespread chronic H. pylori and hepatitis infections remain there, as reported by WE News English.

The pattern holds across Asia. In Southeast Asia, infections sit behind roughly one in six cancers, above the global average, and researchers estimate India alone recorded about 190,000 infection-driven cases in 2024. Most infections linked to cancer cluster in places where the preventive tools are least available — which is exactly why researchers call this a solvable inequity, according to a Particle summary of the study.

What actually lowers your risk

Here is the part that matters for you: many of these cancers never had to happen. HPV and hepatitis B both have effective vaccines. Cervical screening catches HPV-driven cell changes years before they turn dangerous. H. pylori can be found with a simple breath or stool test and cleared with antibiotics, and modern antivirals cure most hepatitis C infections. Public health researchers describe infections linked to cancer as some of the most preventable cancers of all — the payoff comes from scaling up vaccination, screening, and treatment of chronic infections, according to Medical Dialogues.

Doctors who treat these diseases see the same upside. Nina R. Salama, PhD, a researcher at the Fred Hutchinson Cancer Center in Seattle who studies H. pylori but did not take part in the analysis, said the numbers should remind physicians of a blunt fact: that these cancers are, in her words, "an important cause of mortality that they have tools to address," as reported by Medscape.

One caution before anyone panics: carrying one of these infections is not a cancer sentence. Most people infected with HPV or H. pylori never develop cancer — the danger climbs when an infection lingers for years, when the immune system cannot clear it, or when it combines with other risk factors like smoking. The estimates themselves come from population-level math rather than tracking individual patients, so they lean on the quality of each country's cancer records. And because the study counts only infections already proven to cause cancer, the true figure could run higher, according to a Particle summary of the research.

For more on what the science says about protecting your health, browse our health section — including a recent look at how heart risk can hide behind a healthy BMI.