Only 5 infections responsible for more than 2 million new cases of cancer per year: ScienceAlert

Cancer may seem like an inevitable part of life, but many factors can help reduce your risk.

When we think about reducing cancer risk, we usually think about lifestyle factors: smoking, alcohol consumption, exercise.

But a new study by a team of cancer epidemiologists, published in The Lancet Oncologyhighlights how infections actually contribute to your cancer risk.

According to global data, infections were linked to 12% of all cancers diagnosed in 2024. This represents 2.3 million new cases of cancer.

Five key pathogens were responsible for almost all of these infection-related cases.

The most common attacker was stomach bacteria, Helicobacter pylori, which was involved in 4 percent of the total cancers diagnosed in 2024, or 760,000 cases.

H. pylori is a very common bug: statistically speaking, one in two people in the world is infected with it. For most people, infection with H. pylori does not cause any symptoms, but some strains can cause gastric ulcers and ultimately stomach cancer.

Human papillomavirus (HPV) was also associated with 4% of total new cancers diagnosed in 2024, or 750,000 cases.

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Hepatitis B virus (HBV) was linked to 2 percent of new cases, Epstein-Barr virus (EBV) to 1 percent, and hepatitis C virus (HCV) to less than 1 percent.

EBV is a newcomer to this list. Since the release of previous global estimates, the evidence that EBV causes cancer has increased significantly.

It’s quite bizarre to think that these infections, which can already make us very sick, could also lead to cancer, but these findings also give us an opportunity.

They suggest that proper treatment and prevention of these infections could make a very big difference in cancer rates across the world.

“Our updated estimates highlight the continued importance of infection control in global cancer prevention strategies,” note lead author Harriet Rumgay and colleagues.

“Many cancer-causing infectious agents are the subject of existing or potential preventative interventions, including vaccines, diagnostics, treatments, and safe injection practices.”

For many of these pathogens, it’s about making sure that these public health interventions are accessible to people.

“Despite progress in vaccination and screening, infection-related cancers remain a major challenge globally, with persistent inequalities particularly affecting low- and middle-income countries,” the authors add.

Three-quarters of infection-related cancers came from low- and middle-income countries, primarily East Asia, sub-Saharan African countries, and Southeast Asia.

The majority of infection-related cancer diagnoses in 2024 were made in East Asia, accounting for 42% of the global total. Infections linked to these diagnoses were mainly H. pylori and HBV.

Getting more people vaccinated against HPV (especially men, who have often not been targeted by HPV vaccines) and HBV is expected to significantly reduce cancer rates worldwide, but for H. pylorithe answer is not so simple.

“So far, little progress has been made in the development H. pylori vaccines or very effective H. pylori therapies that can minimize ineffective antibiotic exposure, which would have a significant impact on the control of gastric cancer globally,” the authors write.

We also don’t have a vaccine or any other method to control the spread of EBV (which infects about 95 percent of adults), although several vaccine clinical trials are underway.

“Even if investments in the development of new preventive vaccines against EBV, H. pylori, and Kaposi’s sarcoma (another virus-related cancer) is key, many prevention strategies are known to be cost-effective,” the authors write.

“Unfortunately, these strategies are often underutilized due to societal, financial and political barriers, often in the contexts that need them most.

“Given the overwhelming economic and social costs of cancer, investing in prevention is crucial.”

The research was published in The Lancet Oncology.