1 in 8 Cancers Is Caused by an Infection. Here’s What That Means for You

If you have ever wondered whether a chronic infection could be doing something more serious than causing occasional discomfort, a major new analysis published in The Lancet Oncology gives that concern concrete shape. The study quantified how many of the world's new cancer diagnoses in 2024 can be traced directly to infectious pathogens, and the answer is more than 2.3 million cases, or roughly 12 percent of all cancers diagnosed that year. The leading culprits are bacteria and viruses most people have heard of, and for many of them, vaccines and treatments already exist.

Key takeaways:

• 2.3 million new cancers in 2024 were caused by infectious pathogens, representing 12% of all new cases worldwide.
• H. pylori, HPV, and hepatitis B and C viruses together account for the vast majority of infection-driven cancers.
• Existing vaccines (for HPV and HBV) and antibiotic regimens (for H. pylori) mean a large share of these cancers are preventable.
• This data applies unevenly across regions: East Asia and sub-Saharan Africa carry a disproportionate burden.

H. pylori, HPV, and Hepatitis Viruses Drive Most Infection-Linked Cancers

The single largest infectious cause of cancer is Helicobacter pylori, a bacterium (a corkscrew-shaped microbe that colonizes the stomach lining) responsible for 760,000 new cancer cases in 2024, nearly all of them stomach cancers. H. pylori is not rare: estimates suggest more than half the world's population carries it, though most people never develop cancer. The risk concentrates heavily in East Asia, where both infection rates and gastric cancer incidence are highest.

Close behind is human papillomavirus (HPV), a sexually transmitted virus that caused almost 750,000 new cancer cases in 2024. HPV-related cancers include cervical, anal, vulvar, vaginal, and penile cancers. Sub-Saharan Africa carries the highest incidence of HPV-driven cancers, a pattern that maps closely onto lower rates of HPV vaccination coverage in that region.

Hepatitis B virus (HBV) and hepatitis C virus (HCV) are the third major driver, both linked to liver cancer (hepatocellular carcinoma). And Epstein-Barr virus (EBV), the pathogen responsible for mononucleosis, caused 260,000 cancer cases, including nasopharyngeal carcinoma (a cancer of the upper throat behind the nose), some stomach cancers, and Hodgkin's lymphoma.

Why These Numbers Matter for People Managing Chronic Gut and Digestive Issues

For readers who suspect their gut health is connected to a broader health problem, the H. pylori figure deserves particular attention. H. pylori is the dominant microbial driver of chronic gastritis (persistent stomach inflammation) and peptic ulcers, and it is the most common infectious cause of cancer anywhere in the body. A person carrying H. pylori and experiencing recurring upper abdominal pain, bloating, or unexplained nausea has a medically recognized reason to ask their doctor about testing.

The hepatitis virus findings matter for anyone with a history of liver disease, unexplained liver enzyme elevations, or risk factors for HBV or HCV exposure. Liver cancer remains one of the harder cancers to catch early; knowing that a substantial fraction of cases trace to viruses for which we have screening tests and, in HBV's case, a vaccine, shifts what proactive care looks like.

Researchers have also noted, though this study focuses on incidence rather than survivorship, that people dealing with unmet needs after a cancer diagnosis often lack adequate follow-up guidance for the infectious conditions that may have contributed to their cancer in the first place, a gap this kind of population-level data can help address by directing attention and resources.

How Researchers Quantified 2.3 Million Cases

The study team analyzed global cancer incidence data for 2024, then applied established attributable-fraction methods to estimate how many cases of each cancer type could be attributed to a specific infectious pathogen. Attributable fraction is an epidemiological measure that estimates the proportion of cases that would not have occurred if the infection had been absent, based on the known relative risk of cancer among infected versus uninfected individuals combined with the prevalence of infection in each population.

This kind of ecological analysis draws on large surveillance datasets and is well-suited to estimating population-level burden, though it cannot tell you with certainty that any individual's cancer was caused by a specific pathogen. What it does establish clearly is the order of magnitude: more than one in eight cancer diagnoses globally is infection-linked, a figure robust enough to shape public health priorities.

What This Means If You Are Actively Monitoring Your Health

The most actionable part of this finding is the preventability angle. HPV vaccines, when given before exposure, are highly effective at preventing the viral strains responsible for most HPV-related cancers. HBV vaccination has existed for decades and is included in routine childhood immunization schedules in most countries. For H. pylori, standard testing (breath test, stool antigen test, or endoscopy biopsy) is widely available, and confirmed infections can be cleared with a one-to-two-week antibiotic and acid-suppressing regimen.

If you have been diagnosed with chronic gastritis, atrophic gastritis, or a stomach ulcer, or if you have a first-degree relative who developed gastric cancer, asking your physician specifically about H. pylori testing is reasonable and supported by current guidelines. Similarly, anyone with risk factors for hepatitis B or C exposure who has not been screened has a clear case for doing so.

None of this means an infection guarantees a cancer diagnosis. The relationship is probabilistic: infection raises risk, not certainty. But the Lancet Oncology data underscore that these are modifiable risks, not random ones.

Open Questions: Regional Disparities and Pathogen Interactions

The geographic concentration of infection-driven cancers points to the study's most important unresolved question: why do H. pylori rates in East Asia translate to such dramatically higher gastric cancer rates than equivalent infection rates elsewhere? Diet, host genetics, bacterial strain variation, and co-infections all appear to play a role, but the relative weight of each factor is not fully established.

Similarly, researchers do not yet have a clear picture of how co-infection with multiple pathogens (H. pylori and EBV both contribute to gastric cancer, for instance) compounds cancer risk beyond what either infection does alone. Better characterizing these interactions is likely to be a focus of follow-up work. Separately, regulatory and research bodies are increasingly investing in tools to detect and treat infection-linked cancers earlier; the FDA's Breakthrough Devices Program has expanded its oncology portfolio substantially between 2016 and 2024, reflecting growing institutional attention to exactly this problem.

Common Questions

Can you catch a cancer-causing infection without knowing it? Yes. H. pylori, HPV, HBV, and EBV often cause no obvious symptoms for years or decades after initial infection. Many people only discover they are infected during workup for an unrelated problem or routine screening.

If I test positive for H. pylori, does that mean I will get stomach cancer? No. H. pylori infection substantially raises the relative risk of gastric cancer, but the absolute lifetime risk for any individual remains low. Treating the infection reduces that risk further, which is why confirmed H. pylori is generally treated even in asymptomatic people.

Are there gut-health interventions that reduce cancer risk from these pathogens? The established intervention for H. pylori is antibiotics plus acid suppression, not probiotics or dietary changes alone. Some research into the role of microbial therapies in oncology settings is ongoing, but no probiotic or dietary regimen has been shown to substitute for antibiotic eradication of H. pylori.

What about EBV? Is there a vaccine? Not yet for general use. EBV vaccine candidates are in development and have shown early promise, but none has reached the broad deployment stage that HPV and HBV vaccines have.

References

1. www.thelancet.com. https://www.thelancet.com/journals/lanonc/article/PIIS1470-2045(26)00307-4/fulltext
2. Jennifer White, Joanne Park, K. Brooke Russell, et al. (2018). Falling through the cracks. A thematic evaluation of unmet needs of adult survivors of childhood cancers. Psycho-Oncology. https://doi.org/10.1002/pon.4754
3. Kushal T. Kadakia, Sanket S. Dhruva, Joseph S. Ross, et al. (2025). FDA Authorization of Therapeutic Devices Under the Breakthrough Devices Program. JAMA Internal Medicine. https://doi.org/10.1001/jamainternmed.2025.2235
4. Brian P. Hanley, Alejandro J. Betancourt, Gustavo Gross, Wilbur (Bo) Bowne (2026). Perspective on Lessons Not Learned: From Coley’s Toxins to Microbial Drug Delivery, Guidance for Institutional Review Boards (IRBs). International Journal of Molecular Sciences. https://doi.org/10.3390/ijms27135985