About 2.3 million new cases of cancer worldwide were caused by viral, bacterial and parasitic infections in 2024. This represents 12% of all new cancer cases worldwide, according to a new study from the International Agency for Research on Cancer (IARC), the cancer agency of the World Health Organization.
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“Despite advances 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,” said Harriet Rumgay, a scientist at IARC’s Cancer Surveillance Branch and co-author of the study.
“The results highlight the important role that infection control can play in reducing the global burden of cancer,” she added.
The authors recommend measures covering primary prevention, screening, treatment, research and policy, from scaling up existing vaccines and developing new ones to introducing parasite-specific control measures and expanding testing.
Investing in “new prevention tools could have the biggest impact,” said Gary Clifford, co-lead author of the study.
Such future investment could be made for infections such as Epstein-Barr herpesvirus (EBV) – one of the most prevalent human viruses in the world – for which there is no approved vaccine, Clifford said. This infection can cause six different types of cancer, including throat cancer or stomach cancer.
EBV is just one of 12 infectious agents that cause cancer in humans, including viruses, bacteria and parasites.
What are the most common infections?
The main infectious cause of cancer is Helicobacter pylori, a bacteria that infects the stomach, often causing gastric ulcers. It caused 760,000 new cases of cancer in 2024, or 4% of all cases.
This bacteria is associated with three types of cancer: non-cardiac and cardia stomach cancer, as well as a form of non-Hodgkin’s lymphoma that develops there.
Human papillomavirus (HPV) comes in second, responsible for 750,000 new cases, followed by hepatitis B virus (HBV).
HPV can cause eight types of cancer, ranging from cancer of the cervix to the penis to the larynx. The authors noted that all cervical cancers can be attributed to HPV, making this virus a key target for screening and vaccination strategies.
Geographic disparities
Although infection-related cancers can affect anyone, the burden is not shared equally across the world. The study found stark inequalities, with low- and middle-income countries accounting for almost three-quarters of the total.
East Asia recorded the highest number of cancers attributed to infections in 2024, with 990,000 cases, or 42% of the global total – largely due to H. pylori and hepatitis B.
Sub-Saharan Africa has the highest proportion of all regions, with a quarter of all cancers linked to infection, largely due to high rates of HPV-related cancers.
The least affected regions are Northern, Western and Southern Europe, North America and Oceania.
Geographic inequalities also reflect differences in prevention policies and strategies.
The study noted that in East Asia, for example, Japan, South Korea and China have established population-based screening programs using endoscopy to combat high rates of gastric cancer, primarily caused by Helicobacter pylori.
Because endoscopic screening is invasive and expensive, several European countries are piloting H. pylori “screen and treat” programs, which use noninvasive testing to identify an infection and clear it with targeted antibiotics.
Gn Health
