Infections Drive About 2.3 Million New Cancer Cases Annually

A new analysis from the International Agency for Research on Cancer (IARC) estimates that about one in eight new cancer cases worldwide in 2024 — roughly 2.3 million — were attributable to infections. The analysis examined 2024 data and identified twelve infectious agents linked to cancer development, but the findings show that five pathogens account for nearly all of these infection-attributable cases. Helicobacter pylori contributed approximately 760,000 cases, human papillomavirus about 750,000, hepatitis B virus about 360,000, Epstein–Barr virus about 260,000, and hepatitis C virus about 160,000. Together, these five agents represent the overwhelming majority of the 2.3 million total.

The scale of this burden places infections among the leading preventable causes of cancer globally. The estimate that approximately 12.5 per cent of all new cancer diagnoses in 2024 have an infectious origin underscores the public health significance of pathogen-driven carcinogenesis. This proportion translates into millions of individuals whose cancers might be avoided through effective control of the underlying infections. The concentration of cases among a small number of well-characterised pathogens further sharpens the focus for prevention efforts.

Helicobacter pylori, a bacterium that colonises the stomach lining, is the single largest contributor, with an estimated 760,000 cases attributed to it in 2024. Its primary cancer association is with gastric adenocarcinoma, though it is also linked to gastric mucosa-associated lymphoid tissue lymphoma. Human papillomavirus follows closely at roughly 750,000 cases, driven predominantly by cervical cancer but also including cancers of the anus, oropharynx, penis, vulva, and vagina. Hepatitis B virus accounts for about 360,000 cases, almost entirely hepatocellular carcinoma, while hepatitis C virus contributes approximately 160,000 cases, also largely liver cancer. Epstein–Barr virus, a herpesvirus that infects the vast majority of adults worldwide, is estimated to be responsible for around 260,000 cases, including nasopharyngeal carcinoma, certain lymphomas such as Burkitt lymphoma and Hodgkin lymphoma, and a fraction of gastric cancers.

The remaining seven infectious agents identified in the analysis — which include human T-cell lymphotropic virus type 1, Kaposi sarcoma herpesvirus, Clonorchis sinensis, Opisthorchis viverrini, Schistosoma haematobium, and others — collectively account for a small fraction of the total. Their inclusion confirms the diversity of infectious carcinogens but also highlights that the global burden is heavily dominated by the top five.

The analysis reframes the global cancer landscape by quantifying the infectious contribution in a single, updated estimate for 2024. Previous IARC assessments have provided similar attributions for earlier years, but the current figures reflect the most recent incidence data and methodological refinements. The consistency of the finding — that roughly one in eight cancers worldwide stems from infection — across successive analyses reinforces the robustness of the attribution.

From a public health perspective, the identification of the specific pathogens and their associated case numbers provides a quantitative foundation for prioritising interventions. The existence of effective vaccines against human papillomavirus and hepatitis B virus, the availability of antibiotic regimens that can eradicate Helicobacter pylori, and the curative antiviral therapies for hepatitis C virus mean that a substantial portion of the 2.3 million cases are theoretically preventable with existing tools. However, the analysis does not evaluate the current coverage or implementation of these interventions, nor does it project the achievable reduction under real-world constraints.

A critical distinction emerges when considering the preventability of each pathogen's contribution. For Epstein–Barr virus, which accounts for 260,000 cases, no vaccine is yet licensed, and the mechanisms linking infection to oncogenesis are complex and not fully understood, limiting immediate opportunities for primary prevention. This gap means that even with optimal deployment of all currently available measures, a residual burden of infection-attributable cancer would persist.

The geographic distribution of these infections — and consequently of the associated cancers — varies widely, reflecting differences in pathogen prevalence, socioeconomic conditions, healthcare infrastructure, and historical vaccination policies. Regions with high endemic rates of hepatitis B, hepatitis C, Helicobacter pylori, or human papillomavirus bear a disproportionate share of the infection-related cancer burden. The analysis does not break down the 2.3 million cases by region, but the global estimate aggregates these heterogeneous patterns.

Continued monitoring of infection-related cancer trends will be essential to assess the impact of expanding vaccination programmes, improved screening, and increased access to antimicrobial and antiviral therapies. The IARC's 2024 estimate serves as a benchmark against which future progress can be measured. It also highlights the need for sustained investment in research to develop preventive strategies for pathogens such as Epstein–Barr virus, where current tools are insufficient.

In summary, the IARC analysis confirms that infections remain a major driver of global cancer incidence, with 2.3 million new cases in 2024 attributable to twelve infectious agents. Five pathogens — Helicobacter pylori, human papillomavirus, hepatitis B virus, Epstein–Barr virus, and hepatitis C virus — account for nearly all of this burden. The findings quantify a substantial preventable fraction of cancer and underscore the importance of integrating infection control into comprehensive cancer prevention strategies.