A new study published in The Lancet Oncology estimates that infections caused approximately 2.3 million new cancer cases worldwide in 2024—about 12 percent of all new cases—according to research conducted by The International Agency for Research on Cancer (IARC), an arm of the World Health Organization.
The bacterium Helicobacter pylori caused the largest number of infection-linked cancer cases globally, accounting for 760,000 cases predominantly in eastern Asia, primarily by increasing the risk of stomach cancer. Human papillomavirus (HPV) followed closely behind, linked to nearly 750,000 new cases globally with high rates in sub-Saharan Africa. HPV causes 100 percent of cervical cancer cases and also anal, vulvar, vaginal, penile, and some head and neck cancers.
Hepatitis B virus (HBV) and hepatitis C virus (HCV) were also linked to a significant number of liver cancer cases. According to Gary Clifford, a cancer epidemiologist and study co-author, the science has advanced considerably, with researchers identifying new infectious agents as cancer-causing and finding increased evidence about the range of cancers existing agents can cause.
The study expanded its list to include 16 additional infectious agents for the first time. New agents identified include HIV and its link to cervical cancer, and Merkel cell polyomavirus, a rare virus causing an aggressive form of skin cancer. Epstein-Barr virus (EBV) was linked to approximately 260,000 cases globally in 2024, leading to nasopharyngeal cancer, some gastric cancers, and Hodgkin’s lymphoma. Clifford noted that EBV represents “quite a big burden of cancer” that was not previously counted.
The global report highlights vast regional differences, mostly driven by historical disparities. High-income countries with established cancer screening and vaccination programs perform better than lower- and medium-resourced countries where access to prevention and treatment is limited. In North America, the burden of cancer-causing infections is much lower, with H. pylori and HPV being the most common sources.
In Canada, a 2019 study estimated the rate of cancers attributable to infections at 4 percent, leading to more than 7,000 cancer diagnoses annually. Cervical cancer rates had been steadily declining in Canada due to robust childhood vaccination programs, but plateaued last year. Canada’s cervical cancer elimination plan aims to increase vaccination rates to 90 percent and screening rates to 90 percent, though currently only about five provinces are above 80 percent.
Key facts
- Infections caused an estimated 2.3 million new cancer cases worldwide in 2024, representing 12 percent of all new cases
- Helicobacter pylori caused 760,000 cases, predominantly in eastern Asia
- Human papillomavirus (HPV) accounted for nearly 750,000 new cases globally
- Epstein-Barr virus was linked to approximately 260,000 cases in 2024
- In Canada, infections are estimated to cause about 4 percent of cancer cases, or more than 7,000 diagnoses annually
- High-income countries with screening and vaccination programs have lower infection-related cancer burdens than lower- and medium-resourced countries