The short answer: yes. A global analysis published in The Lancet Oncology in late September 2026 found that about 2.3 million new cancer cases in 2024, roughly 1 in 8 of all diagnoses worldwide, can be attributed to infections. Just five infections, Helicobacter pylori, human papillomavirus (HPV), hepatitis B, Epstein-Barr virus and hepatitis C, account for almost the entire burden. Many of the resulting cancers are preventable with tools we already have: vaccines, screening and straightforward treatment.
When we think of what causes cancer, we usually think of smoking, sun exposure and family history. This new research, led by epidemiologist Harriet Rumgay and senior author Gary Clifford at the International Agency for Research on Cancer (IARC), says infections belong on that list too. Here is what the study found, which infections matter most, how an infection can turn into cancer, and what you can do about it.
The 2026 study in numbers
The IARC team estimated the share of 2024’s global cancer cases caused by 12 infectious agents that are classified as definite (Group 1) carcinogens. The headline figures:
- 2.3 million new cancer cases in 2024 attributed to infections
- 12% of all new cancer diagnoses worldwide, about 1 in 8
- 5 infections drive more than 2.2 million of those 2.3 million cases
- More than 20 different cancer types are linked to these infections
The burden is not shared evenly. Roughly three-quarters of infection-linked cancers occur in low- and middle-income countries. Eastern Asia alone accounted for about 990,000 cases in 2024, or 42% of the global total, and its age-standardised incidence rate was the highest in the world at 31.9 cases per 100,000 people, against a worldwide average of 22.7. Sub-Saharan Africa, central and eastern Europe and south-eastern Asia also sat above the global average.
As senior author Gary Clifford put it: “We can intervene before it gets anywhere near cancer… Prevention works.” The question is which infections to act on, and how.
Which infections cause cancer?
Five pathogens account for nearly all infection-attributable cancers. Here they are, with what each one causes and what can be done about it.
1. Helicobacter pylori: the stomach bacterium behind 760,000 cases
H. pylori is the single largest contributor: an estimated 760,000 cancer cases in 2024, about 4% of all cancers globally. It is a bacterium that lives in the stomach lining of a large share of the world’s population, most of whom never notice it. Where it causes harm is in chronic gastritis that can progress over years to stomach cancer, most often non-cardia gastric tumours.
The encouraging part is that H. pylori can be tested for and cleared with antibiotics. The researchers flag test-and-treat strategies, alongside investment in an effective vaccine, as a priority, because no licensed vaccine against it exists yet.
2. Human papillomavirus (HPV): 750,000 cases, mostly cervical
HPV is the second-largest contributor, with roughly 750,000 cases in 2024, also about 4% of global cancers. Around 600,000 of those were cervical cancers. HPV is also linked to cancers of the anus, vulva, vagina, penis and throat. It is one of the most common infections in the world, and persistent infection with high-risk HPV types is what drives cancer risk.
This is the infection where prevention is furthest along: safe and effective HPV vaccines have existed for years, and cervical screening catches precancerous changes before they turn into cancer. Together, vaccination and screening are the reason cervical cancer is one of the most preventable cancers we know of.
3. Hepatitis B: 360,000 cases, mostly liver
Hepatitis B virus was linked to an estimated 360,000 cancer cases in 2024, about 2% of the global total, mostly liver cancers. It is linked to about half of hepatocellular carcinoma, the most common form of liver cancer. Chronic hepatitis B damages the liver over decades, progressing through inflammation and scarring toward cancer.
A hepatitis B vaccine has been available for decades and is now part of routine childhood immunisation in most countries, which makes the ongoing burden a failure of delivery rather than of science. For people already living with chronic hepatitis B, monitoring and antiviral treatment reduce the risk of liver damage.
4. Epstein-Barr virus (EBV): 260,000 cases
EBV, the virus best known for causing glandular fever, was associated with about 260,000 cancer cases in 2024, around 1% of the total. It is linked to 88% of nasopharyngeal cancer, a cancer of the upper throat behind the nose, as well as certain lymphomas. The new analysis elevates EBV as a larger contributor than earlier estimates suggested.
There is currently no vaccine against EBV, though the study authors call for investment in developing one. For now, there is no routine prevention route beyond general awareness of the cancers it is linked to.
5. Hepatitis C: 160,000 cases, with a cure available
Hepatitis C virus was linked to about 160,000 cancer cases, under 1% of the global total, mostly liver cancers: it accounts for roughly a fifth of hepatocellular carcinoma. Unlike the others on this list, hepatitis C can now be cured with a short course of direct-acting antiviral drugs, which makes its ongoing cancer burden almost entirely a matter of finding and treating infections.
How can an infection cause cancer?
The routes differ by pathogen, but they fall into a few patterns. Some viruses insert their own DNA into human cells or disrupt the cell’s normal control systems, so the cell keeps dividing when it should stop. HPV works this way, which is why a persistent infection can, years later, become cervical or throat cancer.
Bacteria take a different route. H. pylori causes long-lasting inflammation in the stomach lining. Chronic inflammation increases the chance of mutations occurring in cells, and over time that damage can create the conditions for cancer. Chronic liver inflammation from hepatitis B and C works on the same principle: decades of repair and regrowth raise the odds that a cell goes rogue.
The common thread is time. These infections almost never cause cancer quickly. Cancer develops after years or decades of persistent infection, which is exactly why prevention and early treatment have so much room to work.
What can you actually do about it?
The researchers’ message is that most of these cancers were avoidable with tools that already exist. The actions that matter:
- Get the HPV vaccine if you or your children are eligible. Check your country’s age recommendations, since catch-up programmes vary.
- Keep up with cervical screening when invited. It catches precancerous changes that can be treated before they become cancer.
- Make sure hepatitis B vaccination is complete, especially for children and for adults in higher-risk groups.
- Get tested for hepatitis B and C if you have risk factors or were born before routine screening programmes began in your country. Hepatitis C is curable; hepatitis B is manageable.
- Ask your doctor about H. pylori testing if you have persistent indigestion or a family history of stomach cancer. A short course of antibiotics can clear the infection.
- Know the symptoms of liver disease, such as persistent fatigue, yellowing of the skin or eyes, and unexplained abdominal pain, and seek care promptly.
What this study does not say
Three caveats keep the headline honest. First, “attributable to infection” is an estimate, not a count of cases where a doctor traced a single patient’s cancer back to a single bug. The researchers combined global infection data with cancer registries to estimate how many cases would not have occurred without these infections.
Second, infection is rarely the only factor. Smoking, alcohol, diet and genetics all shape individual risk, and an infection raises the odds rather than guaranteeing cancer. Most people carrying H. pylori or EBV will never develop cancer.
Third, the prevention picture has real gaps. There is still no licensed vaccine for EBV or H. pylori, and the study’s authors say new investment is needed. Where vaccines and cures exist, the barrier is delivery: the poorest countries carry three-quarters of the burden but have the weakest access to vaccination, screening and treatment.
Frequently asked questions
Can infections cause cancer?
Yes. A 2026 global analysis by the International Agency for Research on Cancer, published in The Lancet Oncology, attributes about 2.3 million new cancer cases in 2024, roughly 12% of all diagnoses, to 12 infectious agents classified as definite carcinogens.
Which infection causes the most cancer?
Helicobacter pylori, a stomach bacterium, tops the list with an estimated 760,000 cancer cases in 2024, just ahead of HPV at 750,000. Together the two account for more than 1.5 million cases, mostly stomach and cervical cancers.
Is cancer contagious?
No. You cannot catch cancer from someone who has it. The infections that raise cancer risk can spread between people, but cancer itself does not. The long gap between infection and cancer is why vaccination and early treatment are so effective.
Does having HPV or H. pylori mean I will get cancer?
No. These infections are extremely common and the large majority of people who carry them never develop cancer. They raise risk over many years; vaccination, screening and treatment bring that risk back down.
Which infection-related cancers are preventable?
Cervical cancer is the standout: HPV vaccination plus cervical screening make it one of the most preventable cancers. Hepatitis B vaccination prevents liver cancer. Hepatitis C can be cured with direct-acting antivirals, and H. pylori can be cleared with antibiotics.
Sources
- Rumgay H et al. Global estimates of infection-attributable cancers, 2024. The Lancet Oncology. 2026.
- CNN: About 1 in 8 cancer cases worldwide are tied to these infections, most of them preventable (5 Oct 2026)
- USA Today: These infections are behind 1 in 8 cancer cases worldwide, study finds (5 Oct 2026)
- New Zealand Doctor / The Conversation: One in eight cancers are likely caused by an infection worldwide, new study
- WebProNews: One in Eight Cancers Traced to Infections as New Data Spotlights Prevention Gaps
- RecaTools: Infections Caused 2.3 Million Cancers in 2024, IARC Finds
This article is for information only and is not medical advice. If you are worried about infections or your cancer risk, speak to a qualified clinician.
