1 in 8 Cancers Are Caused by Infections: What the New Study Means for You

October 1, 2026 avinashmittal

Most people think of cancer as something caused by genes, smoking or bad luck. A major new study adds another cause to the list: infections. Here’s what the research found, which infections that cause cancer matter most, and what you can do to lower your risk.

Quick answer: About 1 in 8 new cancers worldwide in 2024, an estimated 2.3 million cases, were caused by infections, according to a study by the International Agency for Research on Cancer (IARC), the World Health Organization’s cancer agency. Five infections caused almost all of them: H. pylori, HPV, hepatitis B, Epstein-Barr virus and hepatitis C. Many of these cancers can be prevented with vaccines, testing and treatment, and screening.

What the New Study Found

The study, published in The Lancet Oncology on September 28, 2026, used IARC’s global cancer database to estimate how many 2024 cancer cases could be traced back to 12 infections known to cause cancer in humans. The answer was about 2.3 million, or 12% of all new cancer cases worldwide.

IARC scientist Dr. Harriet Rumgay, a co-author, said the findings show the “major role that infection control can play in reducing the global cancer burden.”

The 5 Infections That Cause Most Infection-Related Cancers

Infection	Estimated cancer cases (2024)	Main cancers linked	Prevention or treatment
Helicobacter pylori (bacteria)	760,000	Stomach cancer	Testing and antibiotic treatment; vaccines in development
Human papillomavirus (HPV)	750,000	Almost all cervical cancers; some anal, penile, vaginal, vulvar and throat cancers	HPV vaccine; cervical screening
Hepatitis B virus	360,000	Liver cancer	Hepatitis B vaccine
Epstein-Barr virus (EBV)	260,000	Nasopharyngeal cancer, Burkitt and Hodgkin lymphoma, some stomach cancers	No vaccine yet; candidates in development
Hepatitis C virus	160,000	Liver cancer	Testing and antiviral treatment, which cures most infections

Sources: IARC and Gavi’s summary of the study. Together, these five infections account for almost all cancers caused by infections.

H. pylori: The Biggest Cause

H. pylori is a bacterium that lives in the stomach lining. It’s usually picked up in childhood and can stay for decades if it isn’t treated. According to Gavi, most infected people never get cancer, but long-term inflammation raises the risk of stomach cancer. Antibiotic treatment has been linked to 36% fewer stomach cancers and 22% fewer deaths from the disease in infected people.

HPV: Very Common, Usually Harmless, Sometimes Not

About 80% of people are thought to get HPV at some point, and most infections clear on their own. When certain high-risk types persist, they can cause cancer. HPV vaccines have been shown to cut persistent infections and precancerous changes, and cervical cancer rates are falling in countries that started vaccinating early. A Memorial Sloan Kettering oncologist told Scientific American that HPV-related throat cancer is a growing concern in the U.S.

Hepatitis B and C: The Liver Viruses

Both viruses can cause long-term liver infections that lead to scarring (cirrhosis) and liver cancer. A full course of hepatitis B vaccine gives 98% to 100% protection against infection. There’s no vaccine for hepatitis C yet, but a short course of antiviral drugs cures more than 95% of infections. Because hepatitis C can cause no symptoms for years, many people don’t know they have it.

Epstein-Barr Virus: Nearly Everyone Has It

EBV infects about 95% of people and stays in the body for life, usually without causing problems. The new study ranks it as the fourth-largest infectious cause of cancer, ahead of hepatitis C, partly because of new evidence linking it to some stomach cancers. There’s no licensed EBV vaccine yet.

The Other 7 Cancer-Causing Infections

The study also counted seven less common infections that cause cancer:

Kaposi sarcoma-associated herpesvirus, which causes Kaposi sarcoma
Human T-cell lymphotropic virus type 1, linked to a type of leukemia
Merkel cell polyomavirus, linked to a rare skin cancer
Schistosoma haematobium, a parasitic worm linked to bladder cancer
Two liver flukes, Opisthorchis viverrini and Clonorchis sinensis, linked to bile duct cancer
HIV, which doesn’t cause cancer directly but weakens the immune system and raises the risk of cancers caused by other infections

Where the Burden Is Highest

More than three-quarters (77%) of cancers caused by infections occurred in low- and middle-income countries, where prevention and treatment are harder to reach. Eastern Asia had the most cases, about 990,000 or 42% of the global total, mostly from H. pylori and hepatitis B. In sub-Saharan Africa, infections caused about 1 in 4 new cancers, driven mainly by HPV and Kaposi sarcoma-associated herpesvirus and made worse by HIV.

How to Protect Yourself From Infections That Cause Cancer

IARC says most infection-related cancers can already be prevented with well-established measures. In an interview with Fox News Digital, Dr. Joshua Cohen of City of Hope Orange County also stressed getting treatment or preventive care for infections linked to cancer. Practical steps include:

Get the HPV vaccine at the right age. In the U.S., it’s routinely recommended at age 11 or 12 and can start at 9, with catch-up vaccination through age 26. Adults aged 27 to 45 can decide with their provider, according to the National Cancer Institute’s summary of CDC advisory committee recommendations.
Make sure you’re protected against hepatitis B. Ask your doctor whether you’ve had the full vaccine series.
Get tested for hepatitis C if your doctor recommends it. It’s curable, but only if it’s found.
Treat H. pylori if you have it. If your doctor tests you and finds it, finish the full course of treatment. A gut cleanse or detox won’t clear it.
Keep up with cervical cancer screening, which can find HPV-related changes before they become cancer.
Prevent and treat HIV, which also lowers the risk of cancers linked to other infections.

Recommendations can change, so check what’s right for you with your health care provider.

What Comes Next

The researchers say two things are needed: wider use of the tools that already work, such as vaccines, screening, and testing and treatment, and new vaccines for infections like EBV that have none yet. According to CIDRAP, the authors describe prevention as a question of equity, since the burden falls hardest on countries with the fewest resources.

Frequently Asked Questions

Which infection causes the most cancers?

H. pylori, a stomach bacterium, was linked to about 760,000 cancer cases in 2024, closely followed by HPV with about 750,000.

Can you catch cancer from someone?

No. You can catch some of the infections that raise cancer risk, but most infected people never develop cancer. Cancer itself isn’t passed from person to person.

Can COVID or dengue cause cancer?

Neither COVID nor dengue was among the 12 infections counted in this study as known causes of cancer.

Can HPV cause cancer in men?

Yes. HPV can cause some anal, penile and throat cancers, which is why the vaccine is recommended for boys as well as girls.

Are viruses that cause cancer preventable?

Some are. Vaccines protect against HPV and hepatitis B, and hepatitis C can be cured with antiviral drugs. There’s no vaccine yet for EBV or the other herpesviruses on the list.

The Bottom Line

About 1 in 8 cancers worldwide are caused by infections, and five of them, H. pylori, HPV, hepatitis B, Epstein-Barr virus and hepatitis C, account for almost all of those cases. Many infections that cause cancer can be prevented or treated today, so talk to your provider about HPV and hepatitis B vaccines, hepatitis C testing, H. pylori treatment and regular screening.