Some 2.3 million cancer cases worldwide were attributable to infections in 2024, with five pathogens accounting for almost all cases and low- and middle-income countries bearing the greatest burden.
Infections caused an estimated 12% of all cancers diagnosed worldwide in 2024, highlighting major opportunities for cancer prevention through vaccination, screening, and treatment, according to new research.
The global analysis, published in The Lancet Oncology, was led by researchers at the International Agency for Research on Cancer (IARC).
They found that about 2.3 million new cancer cases were attributable to infectious agents, with Helicobacter pylori and human papillomavirus (HPV) responsible for almost two-thirds of the burden.
“Previous global estimates indicated that approximately 2.2 million cancers worldwide were attributable to infections in 2018, with the highest burden in eastern Asia and sub-Saharan Africa,” the researchers wrote.
“These estimates have informed prevention strategies but, since then, evidence has strengthened on carcinogenicity for additional infectious agents not previously considered (notably HIV and Merkel cell polyomavirus [MCV]) and on causal associations between established Group 1 infectious agents and additional cancer types, such as Epstein–Barr virus (EBV) and gastric cancer.”
The researchers assessed 12 infectious agents classified as carcinogenic to humans, combining GLOBOCAN 2024 cancer incidence estimates with population-attributable fractions for 37 established infection–cancer associations.
H. pylori accounted for the largest number of cases, with an estimated 760,000 cancers, or 4% of all new cancer diagnoses globally.
Human papillomavirus (HPV) followed closely with 750,000 cases (4%), while hepatitis B virus (HBV) accounted for 360,000 cases (2%), EBV for 260,000 cases (1%), and hepatitis C virus (HCV) for 160,000 cases (<1%).
The findings revealed substantial geographical inequalities, with low- and middle-income countries accounting for 77% of infection-attributable cancers.
Eastern Asia recorded the greatest absolute burden, with approximately 990,000 cases, representing 42% of the global total. The region’s burden was predominantly driven by H. pylori, responsible for 410,000 cases, and HBV, which accounted for 260,000 cases.
Sub-Saharan Africa had the highest proportion of cancers attributable to infections, at 25% of all new diagnoses, compared with the global average of 12%. HPV was the leading contributor in the region, accounting for approximately 130,000 cases, or 14% of all cancers diagnosed there.
By comparison, infections accounted for 8% of cancers in high-income countries and 5% in Oceania, where approximately 11,000 infection-attributable cancers were estimated in 2024.
The global age-standardised incidence rate for infection-attributable cancers was 22.7 per 100,000 person-years, rising to 31.9 in eastern Asia and 28.5 in sub-Saharan Africa. Oceania recorded a rate of 16.7 per 100,000.
The analysis also identified marked differences in the cancer types associated with individual pathogens.
Of the 760,000 cancers attributable to H. pylori, approximately 700,000 were non-cardia gastric cancers, representing 85% of all cancers diagnosed at that site.
HPV was responsible for an estimated 600,000 cervical cancers, as well as 58,000 oropharyngeal cancers and 32,000 anal squamous cell carcinomas.
HBV and HCV were predominantly associated with hepatocellular carcinoma, accounting for approximately 330,000 and 130,000 cases respectively.
EBV was linked to a broader range of malignancies, including 110,000 nasopharyngeal cancers, 78,000 gastric cancers, and 47,000 cases of Hodgkin lymphoma.
The researchers noted that EBV had overtaken HCV as the fourth-largest infectious contributor to cancer globally, reflecting expanded evidence of its causal involvement in additional malignancies, particularly gastric cancer and certain lymphomas.
This finding also strengthened the case for developing new preventive interventions, including EBV vaccines.
The researchers said the results demonstrated the continued importance of infection control in cancer prevention, particularly in countries where access to established interventions remained limited.
“Our updated estimates highlight the continued importance of infection control in global cancer prevention strategies,” they wrote.
“Despite progress in vaccination and screening, infection-related cancers remain a major challenge globally, with persistent inequities especially impacting low-income and middle-income countries.
“Our findings emphasise the need to invest in new prevention tools, such as EBV vaccines, and also reinforce the need to scale-up proven interventions, such as HPV and HBV vaccination; testing and treatment of HIV, H. pylori, HBV, and HCV; safe injection practices; access to condoms and pre-exposure prophylaxis to prevent HIV transmission; and screening of precancerous lesions for HPV-driven cervical and anal cancers.
“Many of these strategies are cost-effective and well established, yet remain underutilised due to societal, financial, and political barriers, particularly in settings with the greatest need.
“Tackling infection-related cancers requires coordinated and equity-based strategies within global and local cancer prevention frameworks.”
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However, the authors cautioned that direct comparisons with earlier estimates were complicated by changes in the evidence base and methodology, including the addition of 16 infection–cancer associations not included in the previous analysis.
They also acknowledged limitations arising from differences in the quality and availability of cancer incidence and infection prevalence data across countries. Uncertainty intervals were not calculated because of the heterogeneity of the underlying data sources and methods.
“It is also worth noting that the impact of these infectious agents extends to other non-cancer outcomes that could theoretically be avoidable through primary prevention of these agents,” the researchers noted.
“These conditions include liver cirrhosis for HBV and HCV; multiple sclerosis, mononucleosis, and systemic lupus erythematosus for EBV; and peptic ulcer, dyspepsia, and gastrointestinal bleeding for H. pylori.”
