Lancet Study Finds One in Eight Cancers Worldwide Is Tied to Infection and Most of Those Cases Are Preventable

About one in eight new cancer cases worldwide is linked to an infection, and most of that burden could be reduced with vaccines and treatment already in use, according to an analysis published in The Lancet Oncology.

Researchers estimated that 2.3 million new cancer cases in 2024 were attributable to infections, or 12 percent of all cancers. Helicobacter pylori accounted for the largest share, about 760,000 cases, or 4 percent. Human papillomavirus followed at about 750,000 cases, also 4 percent. Hepatitis B virus was linked to about 360,000 cases, Epstein-Barr virus to about 260,000 and hepatitis C virus to about 160,000.

More than three-quarters of the infection-linked cases were in low- and middle-income countries. Eastern Asia had the largest count, about 990,000 cases, or 42 percent of the global total. Rates were also above the global average in sub-Saharan Africa, Central and Eastern Europe and Southeast Asia.

Harriet Rumgay of the World Health Organization's International Agency for Research on Cancer and colleagues used the Global Cancer Observatory's Cancer Today database to estimate cancers tied to 12 agents already classified as carcinogenic. The list covers viruses, one bacterium and three parasites.

"This recent Lancet data is a profound reminder that a significant portion of our global cancer burden is fundamentally preventable," David Greenberg of Hackensack Meridian Jersey Shore University Medical Center said in a news release. "We have historically siloed infectious diseases and oncology, but they are deeply intertwined. By shifting our focus toward aggressive infection control, we can literally vaccinate and treat our way out of millions of future cancer diagnoses."

HPV, a common sexually transmitted virus, is the leading viral cause. It is tied to cervical, anal, genital and oropharyngeal cancers. A vaccine works best when given in adolescence, before sexual activity. Cervical and anal precancers can also be found on screening.

Chronic hepatitis B can lead to cirrhosis and liver cancer. It is preventable with a vaccine and treatable with antivirals that usually do not cure the infection. There is no vaccine for hepatitis C. Direct-acting antivirals taken for two or three months cure more than 90 percent of patients.

H. pylori, spread by saliva and contaminated food or water, is the most common bacterial cause. Infection is more common in lower-income countries and usually begins in childhood. It causes gastric ulcers and can lead to stomach cancer, a rare lymphoma and possibly colorectal cancer. Antibiotics and acid-reducing drugs can clear it.

Epstein-Barr virus, which causes mononucleosis and stays in the body, is linked to nasopharyngeal cancer, some lymphomas and stomach cancer. More than 90 percent of adults show evidence of infection, usually from childhood. There is no vaccine and no approved antiviral.

HIV is classified as carcinogenic. People with advanced disease can develop Kaposi sarcoma and non-Hodgkin lymphoma. People on antiretroviral treatment with controlled virus still face a higher risk of several cancers. Kaposi-sarcoma-associated herpesvirus, or HHV-8, usually does not cause illness in healthy people but can cause tumors in those with weakened immunity.

The analysis also included human T-cell lymphotropic virus, Merkel cell polyomavirus, the parasitic worm Schistosoma haematobium, which can cause bladder cancer, and two liver flukes, Opisthorchis viverrini and Clonorchis sinensis, which can cause liver and bile-duct cancer.

"Our findings highlight the importance of infection control to achieve cancer prevention," the authors wrote. They listed tools they called scientifically proven and often underused: HPV and hepatitis B vaccination; testing and treatment for HIV, H. pylori, hepatitis B and hepatitis C; safe injection practices; condoms and pre-exposure prophylaxis to prevent HIV; and screening for HPV-driven cervical and anal precancers. They also said the results support investment in new tools, "most notably for EBV."

The gap between what works and what is used is largest where the case counts are highest. Eastern Asia's share reflects both population and the long reach of H. pylori and hepatitis B. Sub-Saharan Africa's higher rates track HIV, HPV and hepatitis. Vaccines and short-course cures do not reach those regions at the same rate as high-income countries.

The estimate is of cases attributable to infection, not of infections that will become cancer. Most people with EBV never develop a related tumor. Most H. pylori infections do not become stomach cancer. The 12 percent figure is the share of new cancers that would not have occurred without the infection, on the study's methods.

Greenberg's claim that the fields have been siloed matches the authors' list. The tools are infectious-disease tools. The outcome they change is a cancer registry. The Lancet paper's number is 2.3 million cases in a year. The prevention case is that a large part of that number is already addressable, and that Epstein-Barr virus is the major agent on the list that still has neither a vaccine nor a treatment.