Infections caused 2.3 million cancer cases in 2024, led by H. pylori and HPV

Pathogen burden in 2024

Infectious pathogens contributed to approximately 2.3 million new cancer cases worldwide in 2024, accounting for roughly 12% (or one in eight) of all cancer diagnoses that year. The findings come from a study conducted by researchers at the International Agency for Research on Cancer (IARC), the specialized cancer division of the World Health Organization based in Lyon, France, and published in The Lancet Oncology. The analysis updates a previous tally completed in 2018, incorporating newer research on the carcinogenicity of infections such as HIV and Merkel cell polyomavirus. According to WHO data, around 20 million people worldwide receive a cancer diagnosis each year, with more than one-third of overall cases preventable through individual behavioral changes.

Harriet Rumgay and her research team at the IARC documented the global impact:

An estimated 2.3 million new cancer cases worldwide were attributable to infections, corresponding to 12 percent of all cancer cases.

Leading biological culprits

The analysis evaluated 12 distinct Group 1 carcinogenic pathogens, which include eight viruses, one bacterium, and three parasitic fluke worms. The single largest individual burdens came from the stomach bacterium Helicobacter pylori, responsible for about 760,000 cases of mostly stomach cancer, and human papillomavirus (HPV), which caused about 750,000 cases, mostly cervical cancer. Together with hepatitis B and hepatitis C, these agents form the primary drivers of infectious malignancies. The only Group 1 pathogen omitted from the analysis was hepatitis D, a satellite virus that exclusively infects individuals who already carry hepatitis B. Other analyzed pathogens include Epstein-Barr virus, Kaposi's sarcoma-associated herpesvirus, human T-cell lymphotropic virus type 1, and the fluke worms Opisthorchis viverrini, Clonorchis sinensis, and Schistosoma haematobium.

Ute Mons, head of the primary cancer prevention department at the German Cancer Research Center (DKFZ) in Heidelberg, reviewed the findings:

Not every infection with these pathogens leads to cancer.

Unlike bacteria, viruses incorporate segments of their genomic information into host cells. This genetic insertion can generate subsequent mutations in genes that foster tumor development, allowing scientists to trace viral genes directly within tumor cell genomes. Additional potential links remain under investigation; for instance, the agency currently classifies the association between the malaria parasite Plasmodium falciparum and Burkitt lymphoma only as probable.

Regional and socioeconomic disparities

The burden of infection-driven cancer varies substantially across geographic regions and income levels. East Asia accounts for 42% of all infection-caused cancer cases worldwide, dominated primarily by Helicobacter pylori and hepatitis B infections. In Sub-Saharan Africa, approximately one in four cancer cases stems from an infection, representing the highest proportional burden on any continent. This African toll is driven predominantly by HPV transmission and exacerbated by high rates of concurrent HIV infection.

More than three-quarters of all infection-related cancers occur in low- and middle-income countries. In these regions, health systems face persistent resource constraints, leaving populations with unequal access to preventive measures and cancer therapies.

Prevention and health interventions

Public health researchers emphasized that most cancers caused by infectious diseases can be avoided through established medical measures. These approaches include routine vaccination programs for HPV and hepatitis B, broad diagnostic testing and medical treatments for Helicobacter pylori and viral hepatitis, expanded HIV care and prevention, and systematic screening initiatives for HPV-related cervical lesions.

Current global adoption of these preventive measures remains uneven. Financial, political, and healthcare delivery obstacles continue to limit access to vaccinations, diagnostic tests, and screening programs in developing and middle-income nations.