Infections cause a lot of cancer. But which infections? And which cancers?

A new analysis of global cancer statistics reveals that 12% of new cancers may be attributable to one of 12 infectious agents. The numbers highlight the role of infection control as an important part of cancer prevention, especially when it comes to a rising global burden of cancer as populations age.The researchers from the International Agency for Research on Cancer (IARC) had previously provided a snapshot of global burden of cancer attributable to infection in 2018. The updated paper includes more infectious agents, including HIV and the Epstein-Barr virus. The latter can lead to nasopharyngeal cancer, some gastric cancers, and Hodgkin’s lymphoma.A total of 2.3 million new cancer cases were caused by infections in 2024, the researchers estimate. This is 12% of all new cancers identified in 2024. The largest number of cases is attributable to Helicobacter pylori. While the burden differed around the world, eastern Asia had 42% of the global total of new cancer cases caused by infection.The researchers analyzed 2024 data from the Global Cancer Observatory Cancer Today (GLOBOCAN) database of cancer incidence. They estimated the proportions, absolute numbers and age-standardized incidences (ASIR) of new cancer cases attributable to 12 infectious agents. The 12 infectious agents are considered Group 1 carcinogens by IARC monographs program.Here are the infectious agents studied and the number of new cases in 2024 attributed to that agent. The most common type of cancer attributed to that infectious agent are in brackets:Helicobacter pylori (gastric cancer): 760,000 casesHuman papillomavirus (HPV) (cervical cancer): 750,000 casesHepatitis B (hepatocellular carcinoma): 357,000Epstein-Barr virus (nasopharyngeal cancers): 264,800Hepatitis C (hepatocellular carcinoma): 158,000HIV (squamous cell carcinoma of the conjunctiva): 81,300Kaposi's sarcoma-associated herpesvirus (Kaposi sarcoma): 34,450Schistosoma haematobium (squamous cell carcinoma of the bladder): 5,900Human T-cell lymphotropic virus (adult T-cell leukemia and lymphoma): 3,900Opisthorchis viverrine or Clonorchis sinensis (intrahepatic cholangiocarcinoma): 3,800Merkel cell polyomavirus (Merkel cell carcinoma): 3,200Infection by many of these viruses, bacteria and parasites can be prevented. Prevention tools includes immunization, safe injection practices, HPV screening and pre- and post-exposure prophylaxis to prevent HIV transmission.While eastern Asia had the highest proportion of global new cases linked to infections (42%), sub-Saharan Africa also had a high proportion at 25%. In both these regions the case numbers were driven by H. pylori infection. Southeastern Asia had 16% of the proportion of global new cases associated with infection, with the burden shared between HPV, Hepatitis B, Epstein-Barr virus and H. pylori. Central and eastern Europe had 10% of the global burden, driven by H. pylori and HPV, a trend also seen in the Americas. The regional differences in the infectious agents causing the cancer cases suggest historical and continuing disparities in public health and healthcare.Canada has an action plan to eliminate cervical cancer through HPV vaccination and screening. The goal is to eliminate new cases by 2040.As for gastric cancers caused by Heliobacter pylori infection, in Canada, researchers predict there will be 4,200 new cases of stomach cancer in 2026, according to projected estimates published in CMAJ. The number of deaths is estimated to be 2,000. Dr. Paul Moayyedi, a gastroenterologist at McMaster University, told CBC News that he wants to see a universal screening program for the bacterium. People at high risk for stomach cancers include those with a family history or those living in First Nations communities. “In consultation with the elders of local communities it would be important to at least offer those groups screening if they would want it,” he said.The paper was published in the Lancet Oncology.

Infections cause a lot of cancer. But which infections? And which cancers?

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