Infections were linked to an estimated 2.3 million new cancer cases worldwide in 2024, accounting for about one in eight diagnoses, according to an analysis by the International Agency for Research on Cancer (IARC).
The study, published in The Lancet Oncology, examined cancer data from the IARC Global Cancer Observatory and assessed the impact of 12 infectious agents known to cause cancer in humans.
Researchers found that Helicobacter pylori was the leading infectious cause, associated with around 760,000 cases, mainly stomach cancer. About 410,000 of those cases occurred in eastern Asia.
Human papillomavirus (HPV) was linked to approximately 750,000 cases, followed by hepatitis B virus with about 360,000. Epstein-Barr virus was associated with roughly 260,000 cases, while hepatitis C virus accounted for around 160,000.
Together, those five infections were responsible for almost all cancer cases attributed to infectious agents in the analysis.
Infection-related cancer burden concentrated in poorer countries
The geographical impact was uneven. Eastern Asia accounted for 42 per cent of infection-related cancers worldwide, largely because of H. pylori and hepatitis B.
The burden was also high in sub-Saharan Africa, where HPV and Kaposi sarcoma-associated herpesvirus were significant drivers, with HIV contributing to the wider health challenge.
More than three-quarters of infection-related cancers occurred in low- and middle-income countries, where access to vaccination, screening and treatment remains unequal.
Harriet Rumgay, a scientist in the IARC’s Cancer Surveillance Branch and a co-author of the study, said the findings highlighted “the major role that infection control can play in reducing the global cancer burden”.
She added that, despite progress in vaccination and screening, infection-related cancers remained a major global challenge, with the burden falling disproportionately on people in low- and middle-income countries.
The overall proportion of cancers attributed to infections has remained broadly stable since IARC’s previous analysis, but the latest study includes newly recognised links, including evidence connecting Epstein-Barr virus with some stomach cancers.
IARC said many of the cancers could be prevented through existing public health measures, including HPV and hepatitis B vaccination, testing and treatment for H. pylori and viral hepatitis, HIV prevention and care, and screening for HPV-related cancers.
The researchers also identified a need for further preventive tools, including vaccines against Epstein-Barr virus and H. pylori, which are not currently available.
They cautioned that the figures were population-level estimates rather than the result of tracking individual patients over time. The analysis also covered only infections already proven to cause cancer, meaning the total impact could be underestimated.
