Infections from viruses, bacteria, and parasites were responsible for an estimated 2.3 million new cancer cases in 2024, accounting for roughly 12% of all cancers diagnosed worldwide. That is the headline finding of a new study by the International Agency for Research on Cancer (IARC), the World Health Organization’s cancer agency.
The study, published in The Lancet Global Health, underscores a persistent global health divide: while infection-related cancers are largely preventable, they continue to exact a heavy toll, particularly in low- and middle-income countries. Harriet Rumgay, a scientist in IARC’s Cancer Surveillance Branch and co-author of the study, said: “Despite progress in vaccination and screening, infection-related cancers remain a major global challenge, with the burden falling disproportionately on populations in low- and middle-income countries.”
Rumgay added: “The findings underscore the major role that infection control can play in reducing the global cancer burden.” The authors argue that a combination of primary prevention, screening, treatment, research, and policy measures could dramatically reduce these numbers.
Prevention tools offer the greatest promise
Gary Clifford, senior co-author of the study, stressed that investing in “new prevention tools could have the greatest impact.” One such tool is a vaccine against the Epstein-Barr herpes virus (EBV), one of the most common human viruses worldwide. EBV is linked to six different cancer types, including throat and gastric cancers, yet no approved vaccine currently exists.
EBV is just one of 12 infectious agents classified as carcinogenic to humans, a list that includes viruses, a bacterium, and parasites. The study’s authors recommend scaling up existing vaccines, developing new ones, introducing parasite-specific control measures, and expanding testing.
Leading infectious causes
The most significant infectious cause of cancer is Helicobacter pylori, a bacterium that infects the stomach and often leads to gastric ulcers. In 2024, it was responsible for 760,000 new cancer cases, or 4% of all cancers globally. H. pylori is associated with three cancer types: non-cardia and cardia stomach cancer, and a form of non-Hodgkin lymphoma that develops in the stomach lining.
Human papillomavirus (HPV) ranked second, causing 750,000 new cases, followed by hepatitis B virus (HBV). HPV can cause eight cancer types, from cervical and penile to laryngeal cancers. The authors noted that all cervical cancers are attributable to HPV, making the virus a key target for screening and vaccination strategies.
Geographical disparities
While infection-related cancers can affect anyone, the burden is far from evenly distributed. Low- and middle-income countries accounted for nearly three-quarters of the total, the study found. Eastern Asia recorded the highest number of infection-attributable cancers in 2024, with 990,000 cases—42% of the global total—largely driven by H. pylori and hepatitis B.
Sub-Saharan Africa had the highest proportion of any region: a quarter of all cancers there were linked to infection, mainly due to high rates of HPV-related cancer. In contrast, Northern, Western, and Southern Europe, North America, and Oceania were the least affected regions.
The disparities reflect differences in prevention policies. In Eastern Asia, for example, Japan, South Korea, and China have established population-based screening programmes using endoscopy to tackle high rates of gastric cancer, primarily caused by H. pylori. These efforts have helped reduce mortality, but the study suggests that broader implementation of such measures could yield even greater gains.
For Europe, the findings serve as a reminder that while the region’s overall burden is lower, pockets of vulnerability remain. The continent’s focus on HPV vaccination and hepatitis B immunisation has been effective, but the study highlights the need for continued investment in prevention, particularly for infections like EBV that still lack vaccines. As the authors note, the potential for new prevention tools is immense—and the time to act is now.
