A recent study published in The Lancet Oncology reveals that infections play a significant role in causing cancer, with around one in eight new cancer cases globally linked to various viruses, bacteria, and other microbes. The research, conducted by experts at The International Agency for Research on Cancer (IARC), found that infectious agents were responsible for an estimated 2.3 million new cancer cases in 2024, representing 12 percent of all new cancer diagnoses.
Among the infections identified, Helicobacter pylori was found to be the leading cause of cancer cases, particularly stomach cancer, with 760,000 cases attributed to this bacterium, mainly in eastern Asia. Human papillomavirus (HPV) closely followed, causing nearly 750,000 new cancer cases globally, including cervical, anal, vulvar, vaginal, penile, and some head and neck cancers, with high prevalence in sub-Saharan Africa. Hepatitis B virus (HBV) and hepatitis C virus (HCV) were also associated with a significant number of liver cancer cases.
The study expanded the list of cancers linked to infections, adding 16 more types to the existing list. Noteworthy findings included the role of Epstein-Barr virus (EBV), which was linked to approximately 260,000 cancer cases globally in 2024, contributing to nasopharyngeal cancer, certain gastric cancers, and Hodgkin’s lymphoma.
According to Gary Clifford, a cancer epidemiologist and study co-author, advancements in science have led to the identification of new infectious agents that can cause cancer. Notably, HIV was linked to cervical cancer, and Merkel cell polyomavirus was associated with an aggressive form of skin cancer.
The global report highlighted regional disparities driven by historical factors. High-income countries with established cancer screening and vaccination programs have fared better compared to lower-resourced regions where access to prevention and treatment is limited. In North America, although the burden of cancer-causing infections is lower, Helicobacter pylori and HPV remain predominant sources.
In Canada, a 2019 study estimated that four percent of cancer cases were attributable to infections. While the prevalence of these infections is lower in Canada, they still contribute to over 7,000 cancer diagnoses annually. Human papillomavirus is closely monitored in Canada, with efforts to increase vaccination rates to combat cervical cancer.
Dr. Paul Moayyedi, a leading gastroenterologist, emphasized the importance of screening for Helicobacter pylori, which is associated with gastric cancers. He advocated for universal screening programs, especially for high-risk groups, to detect and treat the bacterium early, potentially saving lives.