WHO Analysis Finds Preventable Infections Cause One in Eight Cancer Cases Worldwide

Roughly 12 percent of all cancer cases diagnosed globally are caused by preventable infections, according to a comprehensive new analysis by the World Health Organization. The research demonstrates that expanding access to existing vaccines and antibiotics could eliminate millions of future diagnoses.[2][3][5]

The study, published in The Lancet Oncology by the International Agency for Research on Cancer (IARC), linked an estimated 2.3 million new cancer cases in 2024 to infectious agents. Researchers analyzed data from the Global Cancer Observatory to map the worldwide burden.[1][5]

"The findings underscore the major role that infection control can play in reducing the global cancer burden," said Dr. Harriet Rumgay, a scientist in the Cancer Surveillance Branch at IARC and co-author of the study. She noted that infection-related cancers remain a major global challenge despite medical progress.[5]

For many patients, sun exposure, smoking, and family history are the most recognized risk factors for developing tumors. However, the IARC analysis highlights that viruses, bacteria, and parasites are responsible for one in eight cases worldwide, shifting the focus toward communicable disease prevention.[1]

The researchers identified 12 specific infectious agents known to cause cancer in humans. Together, just five of these pathogens—Helicobacter pylori, human papillomavirus, hepatitis B, hepatitis C, and the Epstein-Barr virus—accounted for nearly all of the 2.3 million infection-related cases.[3][5]

The primary pathogens

The bacterium Helicobacter pylori drove the largest share of the global burden, causing an estimated 760,000 cancer cases in 2024. The infection primarily leads to stomach cancer and is highly prevalent in eastern Asia, though it can often be cleared with a simple course of antibiotics.[1][5][6]

Human papillomavirus (HPV) followed closely, responsible for approximately 750,000 new cancer cases globally. HPV is the sole cause of cervical cancer and also drives a significant percentage of anal, vulvar, vaginal, penile, and oropharyngeal cancers.[1][5]

Hepatitis B and hepatitis C viruses are major contributors to liver cancer through long-term tissue damage and chronic inflammation. The IARC analysis linked hepatitis B to roughly 360,000 cancer cases in 2024, while hepatitis C was responsible for an estimated 160,000 cases.[5]

The Epstein-Barr virus, best known for causing mononucleosis, is now recognized as the fourth-leading infectious cause of cancer. The virus was linked to approximately 260,000 cases in 2024, driving nasopharyngeal cancer in Southeast Asia and gastric cancers or lymphomas in Europe and the Americas.[2][4][6]

"This updated analysis shows that the landscape of infection-related cancers continues to evolve as scientific evidence advances," said Gary Clifford, a cancer epidemiologist and senior co-author of the study based in Lyon, France. He noted that researchers are continually identifying new links between known viruses and specific tumors.[1][6]

Mechanisms of cellular disruption

Infections trigger malignant growth through several distinct biological pathways. Some viruses directly alter host cell DNA to promote uncontrolled division, while bacteria and parasites often cause chronic inflammation that damages surrounding tissue over decades.[3]

The updated IARC analysis represents the first time researchers included HIV in their global review of cancer-causing infections. While HIV does not directly mutate host cells, the severe immune suppression it causes leaves patients highly vulnerable to cancers driven by other opportunistic pathogens.[4][5]

Scientists also expanded the list of recognized carcinogenic agents to include the Merkel cell polyomavirus. This rare but potent virus is now definitively linked to an aggressive form of skin cancer, reflecting the growing precision of molecular oncology.[1][5]

Beyond viruses and bacteria, the researchers tracked three parasitic worms known to cause human cancers. Schistosoma haematobium is linked to bladder cancer, while the liver flukes Opisthorchis viverrini and Clonorchis sinensis frequently cause bile duct cancer in specific endemic regions.[3][5]

Karena Volesky, an epidemiologist who led related research in Montreal, emphasized the practical value of the exhaustive pathogen list. "It tells us how important each of the 12 infections are," Volesky said, noting that the data provides a clear roadmap for public health interventions.[1][4]

A stark geographic divide

The burden of infection-related cancer is not distributed evenly across the globe. Approximately 75 percent of these 2.3 million cases occurred in low- and middle-income countries, highlighting severe global inequities in healthcare access and preventive medicine.[3][5]

Eastern Asia accounted for roughly 42 percent of the global total, driven heavily by endemic rates of Helicobacter pylori and subsequent stomach cancers. Improving sanitation and expanding antibiotic access in the region could drastically reduce this specific oncological burden.[1][6]

In sub-Saharan Africa, a different combination of pathogens drives the regional cancer rates. High prevalence of HPV, HIV, and the Kaposi sarcoma-associated herpesvirus creates a compounding effect, making infectious agents a leading cause of mortality across the continent.[1][5]

While North America reports lower overall rates of infection-driven cancers, public health officials remain concerned about lagging vaccination campaigns. Volesky's research estimated that carcinogenic infections still lead to more than 7,000 cancer diagnoses each year in Canada alone.[4]

Clifford emphasized that the geographic data illustrates exactly where international funding must be directed. "It also highlights where future investments in new prevention tools could have the greatest impact, particularly for infections such as EBV, for which effective vaccines are not yet available," he said.[6]

Expanding prevention strategies

Despite the availability of highly effective vaccines for HPV and hepatitis B, immunization rates remain suboptimal in many vulnerable regions. Financial barriers, social stigma, and logistical challenges continue to prevent these life-saving tools from reaching the populations that need them most.[5]

For bacterial drivers like Helicobacter pylori, population-level screen-and-treat programs remain rare. Public health advocates argue that systematically testing for the bacterium and prescribing antibiotics could prevent hundreds of thousands of stomach cancer cases annually.[6]

The World Health Organization has set an ambitious global target to vaccinate 90 percent of 15-year-old girls against HPV by 2030. Achieving that benchmark would effectively eliminate cervical cancer as a public health threat in the coming decades.[3]

Reducing the 2.3 million annual cases will require a dual approach from international health ministries. Governments must scale up the delivery of existing vaccines and antibiotics while simultaneously funding the development of novel immunizations for complex pathogens like the Epstein-Barr virus.[5][6]