Among the most commonly identified contributors to cancer development are tobacco use, alcohol consumption, excess body weight, environmental pollutants, genetic predisposition, and advancing age. Recent research has pointed to infections as a noteworthy contributing factor in this context.
Research published in The Lancet Oncology estimates that roughly 2.3 million newly diagnosed cancer cases globally during 2024 — approximately 12 percent of the total — were attributable to infectious agents. Roughly one in eight cancer cases recorded worldwide that year had an infectious cause.
Drawing on cancer figures from 2024, the International Agency for Research on Cancer (IARC) team examined the role of infection-causing agents in driving cancer development. Twelve pathogens with documented carcinogenic properties in humans were examined by the research. Nearly all cancer cases linked to infection were attributable to a handful of pathogens — just five in total.
Among the pathogens identified were Helicobacter pylori (H. pylori), human papillomavirus (HPV), hepatitis B virus (HBV), Epstein-Barr virus (EBV), and hepatitis C virus (HCV). Of the 2.3 million infection-linked cancer diagnoses recorded in 2024, just five pathogens accounted for the vast majority of cases.
Accounting for approximately 760,000 diagnoses, H. pylori ranked as the leading infectious contributor to cancer development, predominantly through its association with gastric malignancies. Approximately 750,000 diagnoses were attributed to HPV, a virus whose prolonged presence in high-risk strains drives the development of cervical cancer and has also been connected to malignancies affecting the anus, vulva, vagina, penis, and certain regions of the head and neck.
Hepatitis B virus was linked to approximately 360,000 new cancer diagnoses, predominantly involving the liver. Researchers associated EBV with roughly 260,000 diagnoses, spanning certain stomach and nasopharyngeal cancers as well as select lymphoma types. Approximately 160,000 cases were linked to hepatitis C virus, with the majority involving liver cancer.
The revised examination also incorporated more recent data connecting EBV to stomach cancer, alongside further cancer categories and pathogenic agents.
Dr. Harriet Rumgay, a researcher in the Cancer Surveillance Branch at IARC and co-author of the study, noted that the results highlight how infection control measures could contribute to lowering cancer rates worldwide.
Progress in immunisation programmes and early detection methods has brought down rates of infection-linked cancers, yet these conditions remain an ongoing concern for public health systems worldwide, with the greatest concentration of cases found in nations with fewer economic resources. An infection diagnosis does not necessarily lead to a cancer outcome for every person affected.
Whether a particular infection leads to cancer depends on variables such as the pathogen's characteristics, how long it remains active in the body, the individual's immune defences, and additional contributing health factors. Persistent infections may lead to prolonged inflammatory responses or cellular and tissue deterioration over time. Prolonged infection may gradually alter cellular behaviour in ways that raise the likelihood of malignancy developing over time.
Long-term hepatitis B and hepatitis C infections can lead to liver deterioration and elevated susceptibility to hepatocellular disease. Ongoing exposure to high-risk HPV strains can trigger abnormal cellular developments in the cervix that may advance toward cancer when left undiagnosed and untreated. Persistent infection with H. pylori triggers ongoing gastric inflammation and carries a well-established association with the development of stomach cancer.
The IARC data showed that roughly three-quarters of those cancer cases were recorded in lower-income nations. Variations in infection prevalence, vaccination uptake, cancer screening programmes, diagnostic access, and treatment availability are among the factors contributing to this disparity.
Vaccination, routine screening, diagnostic testing, and timely treatment have been identified as tools that can help prevent a range of cancers linked to infectious causes. Research indicates that vaccination against HPV may offer protection from the strains linked to the majority of cervical cancer cases, along with several other malignancies associated with the virus. Early detection through screening can reveal precancerous cervical abnormalities before they progress to invasive disease.
Vaccination against hepatitis B has been shown to lower the likelihood of developing chronic HBV infection, thereby decreasing the probability of liver cancer. While no vaccine exists for hepatitis C, antiviral therapies are able to eliminate the HCV infection in the vast majority of cases. Vaccination, screening, and early treatment are among the preventive tools identified as capable of reducing infection-related cancer rates.
