Infections caused by viruses, bacterium and parasites caused an estimated 2.3 million new cancer cases in 2024, with low- and middle-income countries bearing most of the burden.
Around 2.3 million new cancer cases globally were caused by virus, bacteria and parasite infections in 2024. That’s 12% of all new global cancer cases, according to a new study from the International Agency for Research on Cancer (IARC), the World Health Organization’s cancer agency.
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“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,” said Harriet Rumgay, a scientist in the Cancer Surveillance Branch at IARC and a co-author of the study.
“The findings underscore the major role that infection control can play in reducing the global cancer burden,” she added.
The authors recommend measures spanning 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 greatest impact,” said Gary Clifford, senior co-author of the study.
One such future investment could be done for infections such as Epstein-Barr herpes virus (EBV)— one of the most common human viruses in the world — that doesn’t have an approved vaccine, Clifford said. This infection can cause six different types of cancer, including throat or gastric cancer.
EBV is just one of 12 infectious agents carcinogenic to humans, including viruses, a bacterium and parasites.
What are the more common infections?
The leading infectious cause of cancer is Helicobacter pylori, a bacterium that infects the stomach, often causing gastric ulcers. It caused 760,000 new cancer cases in 2024, 4% of all cases.
This bacterium is associated with three cancer types: non-cardia and cardia stomach cancer, and a form of non-Hodgkin lymphoma that develops there.
Human papillomavirus (HPV) ranked second, responsible for 750,000 new cases, followed by hepatitis B virus (HBV).
HPV can cause eight cancer types, ranging from cervical and penile to laryngeal. The authors noted that all cervical cancers can be attributed 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 not shared equally across the world. The study noted stark inequities, with low- and middle-income countries accounting for nearly three-quarters of the total.
Eastern Asia recorded the most 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, with a quarter of all cancers there linked to infection, largely because of high rates of HPV-linked cancer.
The least affected regions were Northern, Western and Southern Europe, North America and Oceania.
The geographical inequalities also reflect differences in prevention policies and strategies.
The study noted that 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, mainly caused by Helicobacter pylori.
Because endoscopic screening is invasive and expensive, several European countries are piloting H. pylori "screen-and-treat" programmes, which use non-invasive testing to identify an infection and clear it with targeted antibiotics.
