Which Common Infections Are Worth Getting Tested For?

Most people think about smoking, sun exposure and family history when they think about risk. A large new global analysis points to something a good deal more ordinary.

Researchers at the International Agency for Research on Cancer, the specialized cancer agency of the World Health Organization, estimated that 2.3 million new cancer cases worldwide in 2024, or roughly 12 percent of all new cases, were caused by infection. The analysis was published in The Lancet Oncology on Sept. 28, 2026, and the practical reading of it for Canadians is that several common infections on the list are testable, treatable or preventable using tools that already exist in this country.

Key takeaways

The International Agency for Research on Cancer estimates that 2.3 million new cancer cases in 2024, about 12 percent of the global total, were attributable to infection.

The analysis assessed 12 infectious agents already classified as carcinogenic to humans, using the agency's Global Cancer Observatory data.

Five agents account for almost all of the burden, led by Helicobacter pylori at roughly 760,000 cases and human papillomavirus at roughly 750,000.

Hepatitis B virus accounted for about 360,000 cases, Epstein-Barr virus for about 260,000, and hepatitis C virus for about 160,000.

Canadian estimates are considerably lower, with published research attributing about 3.7 percent of Canadian cancers diagnosed in 2015, more than 7,000 cases, to infection.

Vaccination exists for human papillomavirus and hepatitis B, and Helicobacter pylori is detectable by simple testing and treatable with a course of antibiotics.

What Did The New Global Study Actually Measure?

The new global study calculated population-attributable fractions across 12 infectious agents already classified as carcinogenic to humans, drawing on the agency's own Global Cancer Observatory incidence estimates for 2024. That method answers a specific question, which is how many cancer cases would not have occurred in the absence of those infections, rather than describing how many people carry them.

The agency framed its own findings around prevention, noting that a significant proportion of the global cancer burden is preventable through better infection control. Several of the common infections on its list already have a vaccine, a test or a cure available in Canada. The researchers also pointed to limited access to vaccination, screening, diagnosis and treatment, alongside social stigma attached to some infections, as reasons the burden falls unevenly across regions and income levels.

Screening programs are the mechanism through which findings of this kind eventually reach patients, and Canadian provinces move at different speeds on that front, as our reporting on Ontario lowering the colorectal screening age to 45 illustrated.

Which Five Infections Account For Most Of The Burden?

The five infections responsible for almost all attributable cases make a short and fairly familiar list. Helicobacter pylori, a stomach bacterium identified in the early 1980s, topped it at roughly 760,000 cases globally, concentrated heavily in eastern Asia. Human papillomavirus followed closely at roughly 750,000 cases, and it is responsible for nearly all cervical cancers along with anal, vulvar, vaginal, penile and a proportion of head and neck cancers.

Hepatitis B virus accounted for about 360,000 cases and hepatitis C virus for about 160,000, both largely through liver cancer. Epstein-Barr virus accounted for about 260,000 cases and now ranks as the fourth largest infectious cause of cancer globally, ahead of hepatitis C. Epstein-Barr is the outlier on the list because no vaccine or treatment currently exists for it, and researchers describe it for that reason as an increasingly important target for prevention work.

Viruses that persist in the body long after the original illness are more common than most people realize, and the mechanism is familiar from the virus behind chickenpox, which our explainer on spotting shingles symptoms early describes in detail.

How Big Is The Canadian Share Of This Problem?

The Canadian share looks considerably better than the global picture without being negligible. Research led by Canadian epidemiologists estimated that 3.7 percent of the cancers diagnosed among Canadian adults in 2015 were attributable to seven infectious agents, which still amounted to more than 7,000 diagnoses in a single year. Human papillomavirus and Helicobacter pylori accounted for the largest shares of that total.

Provincial analysis points in very much the same direction. Ontario Health has reported that roughly four per cent of new cancers diagnosed in the province in 2013, approximately 3,100 cases, were attributed to seven infectious agents, with human papillomavirus responsible for more than 1,300 of them and Helicobacter pylori for more than 1,000. The same modelling work found that meaningful reductions in the prevalence of hepatitis B, hepatitis C and Helicobacter pylori, combined with higher vaccination coverage, could prevent thousands of Canadian cancers over the following two decades.

Reading numbers like these without panicking is a skill in itself, and the fear that follows a cancer diagnosis or a frightening statistic is something we have written about directly in why the fear never fully leaves after treatment ends.

What Should You Expect From Testing And Treatment?

For most of the agents on this list, testing and treatment are unremarkable procedures rather than major undertakings. Helicobacter pylori can be detected through a blood test, a breath test, a stool sample or an endoscopy, and where it is found, it is treated with a course of antibiotics running roughly two weeks. Most people carrying the bacterium never develop problems from it, although left untreated it can cause ulcers,s and in a minority of people it contributes to stomach cancer.

Hepatitis B and hepatitis C testing is a blood draw; hepatitis C is curable with modern antiviral treatment in the great majority of cases, and hepatitis B is manageable with monitoring and medication. Cervical screening detects the changes caused by human papillomavirus long before they become dangerous, and several provinces have moved to testing that looks for the virus itself rather than for cell changes alone.

Expect your clinician to ask about family history, symptoms and risk factors before ordering anything, since testing is targeted rather than universal in Canada. Be cautious about any service offering to sell you testing or treatment outside that system, a problem Health Canada has acted on before, as our coverage of the injunction against an unauthorized peptide seller described.

What Are The Steps To Take With Your Own Family?

The encouraging part of a study like this is how much of it converts into steps to take at an ordinary appointment rather than into anything dramatic. Working out where your household stands on these common infections takes one conversation rather than a project.

Check whether the young people in your household have completed their human papillomavirus vaccination through the school program or through your province's catch-up schedule.

Ask a physician or pharmacist whether catch-up vaccination makes sense for you personally, since eligibility depends on age and circumstances rather than on a single national rule.

Confirm that your cervical screening is current, and ask which test your province now uses, because several have changed their approach recently.

Raise any family history of stomach cancer or persistent unexplained stomach trouble, and ask directly whether testing for Helicobacter pylori is worth doing in your case.

Request hepatitis testing if you have risk factors, have never been tested, or are unsure whether you were vaccinated against hepatitis B as a child.

Combine these into one appointment rather than five, since a single visit can reasonably cover screening status, vaccination status and testing questions together.

Frequently asked questions

How Do You Get Tested For A Stomach Bacterium In Canada?

Testing is arranged through a family physician or a walk-in clinician and can be done by blood test, breath test, stool sample or endoscopy depending on your situation. Testing is targeted rather than routine in Canada, so expect questions about symptoms and family history first. A positive result is treated with a course of antibiotics lasting about two weeks.

Is Vaccination Against This Virus Free For Young People?

Human papillomavirus vaccination is delivered through publicly funded school programs in every Canadian province and territory, although the grade of delivery and the catch-up rules differ between them. Adults outside the school program may be eligible for publicly funded doses in some provinces and may need to pay in others. Ask a pharmacist or physician about your own eligibility.

Does This Virus Affect Men And Boys As Well?

Yes, and the exposure is not limited to one sex. Human papillomavirus is linked to anal and penile cancers and to a substantial share of head and neck cancers, alongside the cervical, vulvar and vaginal cancers it causes in women. That is the reason Canadian school vaccination programs now include boys rather than girls alone. Vaccination works best when it happens before any exposure occurs.

Who Should Be Screened For Liver Infections In Canada?

Testing is generally recommended for people with specific risk factors, people born in regions where hepatitis B is common, and anybody who has never been tested and is unsure of their vaccination history. Hepatitis C is curable with antiviral treatment in the great majority of cases, and hepatitis B is manageable with monitoring, so testing is worthwhile on both counts.

How Common Is This Stomach Bacterium In Canada?

Stomach cancer is far less common in Canada than in parts of eastern Asia, which is why screening for the bacterium behind much of it is targeted here rather than universal. That distribution is also why clinicians who advocate wider testing focus on higher-risk groups, including people with a family history of the disease, rather than on the general population.

What Is Your Next Step From Here?

Your next step fits inside one appointment, so book it and bring the list. Medimap can help you find a family practice clinic near you, compare walk-in clinics with wait times you can check before leaving, or locate a pharmacy offering vaccination. For more coverage of the screening decisions Canadians face, including our explainer on the skin cancer signs that do not look like the pictures, visit the Medimap Health Hub.

Sources: findings and figures from the International Agency for Research on Cancer announcement of its global analysis of cancers attributable to infections, published in The Lancet Oncology on Sept. 28, 2026, with Canadian and provincial estimates from Ontario Health's report on the burden of cancer caused by infections and the McGill and McMaster research on infection-attributable cancers in Canada.

Disclaimer: This article is for general information and is not medical advice, a diagnosis, or a substitute for care from a qualified health professional. Medimap does not prescribe medication or provide treatment. Screening and vaccination eligibility vary by province, so confirm details with your own clinician. If you are experiencing a medical emergency, call 911 or go to your nearest emergency department.