IARC Study Finds 2.3 Million Cancer Cases Linked to Infections in 2024

By Emily Carter | Health & Science Correspondent | October 1, 2026

An estimated 2.3 million new cancer cases linked to infections were recorded worldwide in 2024, accounting for about 12% of all new cancer diagnoses, according to a new study from the International Agency for Research on Cancer (IARC), the cancer research agency of the World Health Organization.

The analysis, published in The Lancet Oncology, examined global cancer data and assessed cancers attributable to infectious agents known to be carcinogenic. In simpler terms, the researchers estimated how many cancer cases were associated with infections that can contribute to cancer development.

The finding does not mean that cancer is generally an infectious disease. It also does not mean that someone who has HPV, Helicobacter pylori, hepatitis B, hepatitis C or Epstein-Barr virus will necessarily develop cancer.

Instead, the study measures the population-level cancer burden linked to specific infections. The results also point to an important public-health opportunity because several infection-related cancers can be reduced through vaccination, screening, testing, treatment and other prevention measures.

What the IARC Cancer Study Found

The new IARC cancer study used 2024 incidence estimates from the Global Cancer Observatory. Researchers calculated population-attributable fractions, which estimate the share of cancer cases associated with particular infectious agents at the population level.

The researchers assessed 12 infectious agents classified by IARC as carcinogenic to humans. The analysis also incorporated newer evidence connecting established infectious agents with additional cancer types.

Overall, approximately 2.3 million cancer cases were attributable to infections in 2024. That represented about 12% of all new cancer cases worldwide.

Put another way, roughly one in every eight newly diagnosed cancers globally was linked to one of the infectious agents included in the analysis.

The study provides a worldwide assessment broken down by factors including country, sex and age. It also shows that the burden is not distributed evenly across the globe.

That difference is important. Infection-related cancer rates depend not only on whether an infectious agent is present, but also on vaccination coverage, screening, access to healthcare, infection treatment and broader socioeconomic conditions.

H. Pylori and HPV Account for the Largest Share

Five infectious agents accounted for most of the cancer burden identified in the study. Helicobacter pylori, commonly known as H. pylori, was associated with approximately 760,000 cancer cases.

Human papillomavirus, or HPV, followed closely with about 750,000 cases. Hepatitis B virus was associated with roughly 360,000 cases, while Epstein-Barr virus accounted for approximately 260,000 and hepatitis C virus for about 160,000.

Together, these figures show why infection control has become an important part of modern cancer prevention.

However, the individual infections are linked to different cancers and operate through different biological mechanisms.

H. Pylori and Stomach Cancer

H. pylori is a bacterium that can colonize the stomach. Long-term infection can contribute to chronic inflammation and changes in the stomach lining, which can increase the risk of stomach cancer in some people.

The presence of H. pylori does not mean that a person will develop cancer. Many infected people never develop cancer, and individual risk depends on multiple factors.

Importantly, H. pylori infection can be detected and treated. Appropriate testing and treatment can therefore form part of cancer-prevention strategies in populations and patients for whom medical evaluation is recommended.

HPV and Cervical Cancer

HPV was associated with approximately 750,000 cancer cases in the 2024 analysis. Persistent infection with certain high-risk HPV types is the main cause of cervical cancer and is also associated with several other cancers.

HPV vaccination is one of the clearest examples of how an infectious-disease vaccine can also become a cancer-prevention tool. Cervical cancer screening provides another important layer of protection by identifying abnormal cells or high-risk HPV infections before invasive cancer develops.

The broader lesson is that preventing an infection can sometimes prevent the chain of biological changes that eventually leads to cancer.

Hepatitis Viruses and Epstein-Barr Virus Also Matter

Hepatitis B virus, or HBV, was associated with about 360,000 cancer cases in the IARC analysis. Chronic HBV infection can damage the liver over time and increase the risk of liver cancer.

An effective hepatitis B vaccine is available and is an established tool for preventing HBV infection. Expanding vaccination coverage is therefore an important part of reducing future liver cancer linked to the virus.

Hepatitis C virus, or HCV, accounted for approximately 160,000 infection-attributable cancer cases in the study. Like chronic hepatitis B, long-term hepatitis C infection can contribute to liver cancer.

There is currently no widely used vaccine against hepatitis C. However, highly effective antiviral treatments can cure most hepatitis C infections when appropriately diagnosed and treated.

Epstein-Barr virus, or EBV, was linked to approximately 260,000 cases. EBV is associated with several cancers, including certain lymphomas and nasopharyngeal cancer. The updated IARC analysis also incorporated newer evidence connecting EBV with some stomach cancers.

Most people exposed to EBV do not develop cancer. The cancer associations identified by researchers apply to particular biological and population-level relationships, not to every person who carries the virus.

Which Cancers Are Linked to Infections?

The cancer types associated with infectious agents vary depending on the pathogen.

Cervical cancer has one of the clearest infection-related pathways because persistent high-risk HPV infection is its main cause. Stomach cancer is strongly associated with H. pylori, while chronic hepatitis B and hepatitis C infections are important causes of liver cancer.

Other infection-related cancers include certain lymphomas, nasopharyngeal cancer and several anogenital and head and neck cancers associated with HPV.

The IARC analysis also included additional infectious agents and cancer associations beyond the five largest contributors. These include HIV, Merkel cell polyomavirus and several parasitic and other infectious agents classified as carcinogenic.

The result is a much broader picture of infection-related cancer than simply counting cancers caused by common viruses.

Why the Infection-Related Cancer Burden Is Unequal

The study found the largest absolute burden of infection-attributable cancer in Eastern Asia, where approximately 990,000 cases were linked to infections. That represented about 42% of the global total identified in the analysis.

Age-standardized incidence rates were also higher than the global average in sub-Saharan Africa, Central and Eastern Europe, and Southeastern Asia.

Low- and middle-income countries carried the majority of infection-related cancer cases. The study estimated that about 77% of these cases occurred in those countries.

That difference does not mean people in poorer countries are inherently more vulnerable to cancer. Instead, it reflects a combination of factors, including infection prevalence, vaccination coverage, screening access, testing, treatment availability and healthcare infrastructure.

When preventive services are difficult to reach, infections that can contribute to cancer may remain undiagnosed or untreated for longer periods.

The same problem can affect cancer screening. If precancerous changes are not detected early, opportunities to prevent or treat disease can be missed.

Why Some Infection-Related Cancers Can Be Prevented

One of the most important findings from the study is that several established prevention tools already exist.

HPV vaccination can prevent infection with high-risk HPV types that cause cervical cancer and contribute to other cancers. Hepatitis B vaccination can prevent HBV infection and reduce the long-term risk of related liver disease and cancer.

Other strategies involve identifying and treating infections. These include appropriate testing and treatment for H. pylori, hepatitis B, hepatitis C and HIV.

For HPV-related cervical cancer, screening can identify high-risk infections or precancerous changes before invasive cancer develops. Safe injection practices and measures that reduce infectious transmission can also contribute to prevention.

These tools do not eliminate every infection-related cancer. However, the study shows that a meaningful portion of the global cancer burden is connected to infections for which prevention or treatment strategies already exist.

Vaccination Is a Major Cancer Prevention Tool

The connection between vaccination and cancer prevention is particularly clear with HPV and hepatitis B.

HPV vaccination targets infections that can later contribute to cervical and other cancers. Hepatitis B vaccination works earlier in the disease pathway by preventing the chronic infection that can contribute to liver cancer.

However, vaccines are not currently available for every infectious agent associated with cancer. There is no widely used vaccine for hepatitis C, H. pylori or EBV.

Researchers continue to study additional prevention tools, including potential vaccines for some of these infections. That research is important, but experimental approaches should not be confused with currently available medical interventions.

For readers interested in the broader cancer research landscape, latest progress in mRNA cancer vaccines offers another example of how researchers are exploring new approaches to cancer prevention and treatment.

What the Findings Mean for Global Cancer Prevention

The IARC study adds infection control to the larger conversation about cancer prevention.

Cancer prevention is often associated with factors such as tobacco use, alcohol consumption, diet, physical activity and environmental exposures. Those factors remain important. However, infectious agents represent another major and partly preventable contributor to cancer worldwide.

The researchers argue that expanding proven interventions could reduce the future burden of infection-related cancers. That includes stronger vaccination programs, wider access to screening, better testing and treatment, and improved infection-control measures.

The challenge is implementation. A prevention method can be highly effective in clinical research but have a smaller population impact when people cannot access vaccines, screening or treatment.

For that reason, the study also highlights the importance of health-system capacity and equitable access to prevention.

The findings should also be considered alongside other cancer research. For example, research into new cancer treatments illustrates the wider scientific effort to improve outcomes after cancer develops.

What Readers Should Know About Infections and Cancer

The headline number can be easy to misunderstand.

Having an infection does not automatically mean a person will develop cancer. Cancer usually develops through a complex combination of biological, genetic, environmental and behavioral factors.

The IARC study instead estimates the number of cancer cases that can be attributed to specific carcinogenic infections at the population level.

That distinction is especially important for infections such as HPV, EBV and H. pylori, which are common but do not result in cancer for most infected people.

The public-health message is therefore not that infections inevitably lead to cancer. It is that controlling certain infections can prevent some cancers.

Vaccination, appropriate screening, testing and treatment are already available for several major infection-related cancer pathways. Expanding access to those tools could help reduce the global cancer burden, particularly in regions where prevention services remain limited.

The new IARC analysis ultimately shows that cancer prevention extends beyond lifestyle changes. For millions of cases worldwide, controlling carcinogenic infections is also an important part of reducing cancer risk at the population level.