Infections play a larger role in cancer than many people realize

A new analysis has sharpened an old public-health message: some cancers are linked to infections, and several of those infection-related cancers are at least partly preventable. The research estimates that about 12% of new cancer cases worldwide in 2024 were attributable to infectious agents.

That does not mean infection explains all cancer risk, and it does not mean most infections lead to cancer. But it does mean that vaccination, testing, treatment and safer exposure practices can make a real difference for some of the most common infection-linked cancers.

What the new analysis found

The study, published in The Lancet Oncology and indexed in PubMed, estimated that about 2.3 million new cancer cases in 2024 were attributable to 12 infectious agents classified as Group 1 carcinogens by the International Agency for Research on Cancer. The list included Helicobacter pylori, human papillomavirus, hepatitis B virus, hepatitis C virus, Epstein-Barr virus, HIV and several less familiar parasites and viruses.

The estimate is global, not U.S.-specific, and it is based on incidence modeling rather than direct measurement of every case. Still, it reinforces a practical point: some infections are established cancer causes, not just temporary illnesses.

Why it matters

Infection-related cancers are important because prevention tools already exist for several of the main infectious causes. CDC guidance says HPV vaccination helps prevent the infections that most commonly cause cancer, and hepatitis B vaccination helps prevent a virus that can lead to liver cancer. For Helicobacter pylori, evidence also supports testing and treatment as a way to lower stomach-cancer risk in appropriate settings.

For people reading a health story like this, the key takeaway is not to panic about every infection. It is to recognize that some routine preventive steps can lower risk before cancer develops.

What the evidence actually shows

HPV

Human papillomavirus is one of the clearest examples of infection-related cancer prevention. CDC says persistent HPV infection can cause cervical, vaginal, vulvar, penile, anal and oropharyngeal cancers, and that vaccination helps prevent the HPV types that most commonly cause cancer. The CDC also notes that studies in the United States and other countries show HPV vaccination is already preventing cancer-causing infections and precancers.

This is strong preventive evidence because the vaccine blocks infection before it can persist. It is not a treatment for existing HPV infection, and it does not eliminate the need for routine screening where recommended.

Hepatitis B

Hepatitis B is another well-established cancer-related infection. CDC says chronic hepatitis B can lead to liver cancer, and that hepatitis B vaccine is safe and effective and recommended for almost everyone. Preventing infection matters because chronic infection can linger for years before causing symptoms, while liver damage may already be developing.

Helicobacter pylori

Helicobacter pylori is a stomach bacterium linked to gastric cancer. A Cochrane review found that eradicating H. pylori in healthy asymptomatic people reduced the later development of gastric cancer compared with placebo or no treatment. Other reviews and government summaries say screening and treatment can be a promising prevention strategy, especially in higher-risk settings.

That said, broad population-wide screening is not routinely recommended everywhere. The National Toxicology Program notes that in the United States, where stomach-cancer risk is relatively low, general-population screening and treatment programs are not recommended at this time. This is one reason the prevention approach has to be matched to risk and local disease patterns.

Other infections

The broader estimate also included infections such as Epstein-Barr virus and HIV. These associations matter, but the prevention picture is less straightforward than it is for HPV or hepatitis B. For some of these infections, there is no vaccine that prevents the cancer-linked infection itself, and risk reduction may depend more on infection control, HIV treatment, or managing immune suppression.

What remains uncertain

Even good epidemiology has limits. The new analysis estimates how much cancer is attributable to infection worldwide; it does not prove that every individual cancer in the count was caused solely by that infection. It also does not mean infection prevention would eliminate cancer, since many cancers have multiple causes, including smoking, alcohol use, obesity, genetics and environmental exposures.

There is also variation by region. The biggest infection-related cancer threats are not the same everywhere, and the best prevention strategy can depend on vaccine coverage, access to testing, antibiotic resistance patterns and local cancer rates.

Practical context: what can lower risk

For most adults, the most actionable steps are familiar public-health measures rather than anything exotic. Staying current on recommended vaccines is one of the simplest ways to reduce infection-related cancer risk. HPV vaccination helps prevent several cancers linked to HPV, and hepatitis B vaccination helps prevent chronic infection that can lead to liver cancer.

For stomach-cancer prevention, discuss H. pylori testing if you have symptoms, a personal history that raises concern, or if a clinician thinks you live in or come from a higher-risk setting. If testing is positive, treatment can reduce the infection burden and may lower future cancer risk.

Safer sex practices, not sharing items that can carry blood exposure, and routine medical care for chronic infections also matter. In some settings, treatment of HIV or hepatitis C can lower the long-term consequences of infection, although the exact cancer-prevention benefit depends on the infection and the cancer type.

When to seek care

Most infections linked to cancer do not cause immediate alarm. But if you have persistent trouble swallowing, unexplained weight loss, ongoing stomach pain, blood in the stool or vomit, jaundice, or a lump, contact a clinician promptly. Those symptoms are not proof of cancer, but they do deserve timely evaluation.

The bottom line

The new analysis adds momentum to a straightforward idea: some cancers are preventable because some of their infectious causes are preventable. Vaccination remains the strongest tool for HPV and hepatitis B. Testing and treatment can also matter, especially for H. pylori in the right clinical context. The evidence does not remove the need for cancer screening or broader healthy-lifestyle prevention, but it does show that infection control is an important part of cancer prevention.