1 in 8 Cancer Cases Linked to Infections, New Study Finds

Approximately 1 in 8 cancer cases diagnosed worldwide in 2024 were driven by infections with viruses, bacteria, or parasites, according to a study published on September 28 in the journal The Lancet Oncology. Researchers at the International Agency for Research on Cancer, an arm of the World Health Organization, mapped the global impact of 12 cancer-causing pathogens and estimated they accounted for about 2.3 million new cancer cases that year. The findings suggest a significant proportion of the global cancer burden could be avoided through improved infection control and vaccination.

Pathogens Fueling Global Cancer Rates

A bacterium called Helicobacter pylori led the list with 760,000 cases, primarily involving gastric cancers concentrated heavily in Eastern Asia. Human papillomavirus followed closely behind with 750,000 cases, encompassing cervical, anal, vulvar, vaginal, and penile cancers and some head and neck cancers. Hepatitis B virus accounted for 360,000 cases driving liver cancers, while the Epstein-Barr virus drove 260,000 cases tied to nasopharyngeal cancer, some gastric cancers, and Hodgkin lymphoma. Hepatitis C virus added another 160,000 cases mostly linked to liver cancer.

Global Disparities in Prevention and Screening

The global impact of infection-driven cancers highlights stark regional and economic disparities.

The Debate Over Infection Risk Estimates

While the study calculates that infections account for 12% of worldwide cancer diagnoses, experts disagree on whether that figure captures the true scope. Dr. Patrick Moore, chair in Innovative Cancer Research at the University of Pittsburgh, told Newsweek that the estimates may be very conservative, adding that the actual fraction of cancers caused by infection is likely larger. On the other hand, Karl Munger, a professor of developmental, molecular and chemical biology at Tufts University, noted to Newsweek that the estimate was lower than expected, pointing out that other analyses have suggested infection-associated cancers account for 15% to 20% of cases globally, though proportions remain considerably lower in the United States and other high-income countries.

Low Vaccine Coverage and Research Gaps Hinder Cancer Prevention

Efforts to curb these cancers face distinct hurdles depending on the pathogen. While vaccines exist for HPV and hepatitis B, coverage remains well below targets, with the World Health Organization reporting that just 31% of eligible adolescent girls worldwide received at least one dose of the HPV vaccine in 2024. Meanwhile, no approved vaccine exists yet for the Epstein-Barr virus.