Researchers at the International Agency for Research on Cancer report that infections caused an estimated 2.3 million new cancer diagnoses worldwide in 2024. The findings, published in The Lancet Oncology, link approximately 12 percent of all global cancer cases to pathogens such as Helicobacter pylori and human papillomavirus.
Led by researchers at the International Agency for Research on Cancer (IARC), which operates as an arm of the World Health Organization, the study evaluates incidence data from the Global Cancer Observatory database to capture how viruses, bacteria, and parasites drive malignancies globally.
The Five Pathogens Driving Most Cases
While the analysis associates infections with more than 20 different types of cancer, a small group of five key pathogens accounts for the vast majority of those 2.3 million cases. At the top of the list is Helicobacter pylori, a common stomach bacterium linked to around 760,000 cases of gastric cancer, with heavy concentrations in eastern Asia where roughly every second person carries the bug.
Human papillomavirus (HPV) follows closely behind with approximately 750,000 cancer diagnoses globally in 2024. While HPV is responsible for every cervical cancer case, it also causes anal, vulvar, vaginal, penile, and specific head and neck cancers. Hepatitis B virus (HBV) contributed to 360,000 liver cancer cases, Epstein-Barr virus (EBV) accounted for 260,000 diagnoses spanning nasopharyngeal cancer and Hodgkin lymphoma, and hepatitis C virus (HCV) was linked to 160,000 cases.
Cellular Mechanisms and New Additions to the List
The updated incidence figures reflect not only improved global data collection but also an expanded roster of recognized pathogens. For the first time, researchers factored in human immunodeficiency virus (HIV) and the rare skin cancer driver Merkel cell polyomavirus, alongside growing evidence connecting Epstein-Barr virus to certain gastric cancers.
According to study co-author Gary Clifford, infectious agents hijack the cellular machinery that controls the normal cell cycle in order to help their own replication
while disabling pathways designed to repair mutated genes or trigger cell death. Other microorganisms, such as the stomach bacterium H. pylori or liver-infesting parasitic worms, induce chronic inflammation and repeated tissue damage that forces rapid cellular repair, increasing the likelihood of genetic mutations.
This fraction, one in eight cancer patients, is the same fraction as lung cancer in all cancers in the U.S. It is not a rare or insignificant problem.
Dr. Patrick Moore, chair in Innovative Cancer Research at the University of Pittsburgh
Global Disparities and Preventable Burdens
The burden of infection-linked malignancies is distributed unevenly across regions.
Experts note that targeted public health measures could alter these trajectories. Expanding neonatal HBV vaccination in Asia, improving HPV immunization coverage for both adolescents and males, and scaling up screening and treatment for hepatitis C offer immediate pathways to drive down cases.
