Summary
A groundbreaking Lancet Oncology study reveals that infections cause 1 in 8 cancers globally, equivalent to 2.3 million cases annually. In Canada, microbes like HPV, H. pylori, Hepatitis B/C, and Epstein-Barr cause over 7,000 preventable cancers each year. Canadians can protect themselves through routine vaccinations, provincial screenings, Hepatitis testing, and antibiotic treatments for stomach bacteria.
When most people think of cancer risk factors, smoking, sun exposure, genetics, and diet usually come to mind. However, major new research highlights another critical factor: preventable infections.
According to a global study published in The Lancet Oncology by the World Health Organization’s International Agency for Research on Cancer (IARC), about 1 in 8 new cancer cases worldwide (12% of the global total, or an estimated 2.3 million cases in 2024) are caused by viruses, bacteria, and parasites.
While low- and middle-income regions bear the heaviest burden globally (accounting for 77% of these cases), the findings hold essential lessons for healthcare consumers here in Canada.
The Top Infections Linked to Cancer
Advances in medical research have expanded the list of known cancer-causing bugs. The study highlights 12 infectious agents classified as top-tier (“Group 1”) carcinogens. Five main microbes account for the vast majority of these cases globally:
- Helicobacter pylori (H. pylori) – Bacteria
- Global Impact: 760,000 cases in 2024 (the #1 infectious cause globally).
- Associated Cancers: Responsible for 85% of stomach (gastric) cancers that occur outside the upper stomach area.
- How it Spreads: Transmitted through close personal contact, crowded living conditions, or unhygienic environments during childhood. It causes chronic stomach inflammation that can eventually turn cancerous.
- Human Papillomavirus (HPV) – Virus
- Global Impact: 750,000 cases in 2024.
- Associated Cancers: Causes more than 99% of cervical cancers, as well as a large share of anal, throat, mouth, vaginal, vulvar, and penile cancers.
- How it Spreads: Transmitted through intimate skin-to-skin sexual contact.
- Hepatitis B (HBV) and Hepatitis C (HCV) – Viruses
- Global Impact: Over 520,000 liver cancer cases combined each year.
- Associated Cancers: Primarily liver cancer (hepatocellular carcinoma) and bile duct cancer.
- How it Spreads: Transmitted through infected blood or bodily fluids, unsterilized medical or tattooing equipment, and shared needles.
- Epstein-Barr Virus (EBV) – Virus
- Global Impact: 260,000 cases in 2024.
- Associated Cancers: Upper throat (nasopharyngeal) cancer, certain stomach cancers, and blood cancers like Hodgkin lymphoma and Burkitt lymphoma.
- How it Spreads: Spread through saliva (often known as the virus behind “mono”). Because almost all adults carry EBV, scientists are prioritizing research into new vaccines.
The Canadian Picture
In Canada, our robust public health infrastructure keeps our infection-related cancer burden significantly lower than the global average, accounting for roughly 4% of all cancer diagnoses (over 7,000 cases annually). However, health experts stress that many of these cases are preventable or treatable if caught early.
- HPV Screening & Vaccines: Canada aims to eliminate cervical cancer by 2040 through school vaccination and routine screening. However, provincial vaccination rates vary (66% to 80+%), and gender-neutral vaccination is crucial because HPV also drives throat, mouth, and anal cancers in men.
- Stomach Cancer & H. pylori: With ~2,000 Canadian stomach cancer deaths annually, experts are pushing for “screen-and-treat” antibiotic programs for high-risk groups, including people with a family history of stomach cancer and First Nations communities.
- Hepatitis B & C (Liver Protection): An estimated 262,000 Canadians live with chronic hepatitis B, and 214,000 Canadians live with chronic hepatitis C, which is a major cause of liver cancer in Canada. Because modern oral medications can cure Hepatitis C in just a few months, Canadian guidelines recommend a one-time blood test for adults born between 1945 and 1975 or anyone exposed to unsterilized needles or pre-1990 blood products.
- Epstein-Barr Virus (EBV): Over 90% of Canadians carry EBV. While no vaccine or clearing treatment exists yet, tracking EBV is a top priority for Canadian researchers studying its links to lymphomas, stomach cancer, and autoimmune diseases like Multiple Sclerosis.
Taking control of your long-term health begins with understanding that many cancers are not purely written in our genes or dictated by chance. Because infectious agents like HPV, H. pylori, and Hepatitis B and C are biological drivers, they represent some of the most treatable and preventable targets in modern medicine.
By staying up to date on routine vaccinations, participating in recommended provincial cancer screenings, and discussing persistent stomach or digestive symptoms with a primary care provider, Canadians can take active, proven steps to protect themselves and their families before an infection ever has the chance to turn into cancer.
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