Researchers at the International Agency for Research on Cancer found that infections caused 2.3 million new cancer cases worldwide in 2024. The figure represents 12 percent, or roughly one in eight, of all new cancers diagnosed globally that year.
Five specific pathogens accounted for the vast majority of those cases, according to the analysis published by Newsweek. Scientists behind the study stated that better infection control measures could prevent a substantial portion of the global cancer burden.
The International Agency for Research on Cancer, based in Lyon, France, is the specialized cancer agency of the World Health Organization. Its researchers analyze global health data to evaluate environmental, lifestyle, and biological causes of cancer.
Dr Patrick Moore, chair of innovative cancer research at the University of Pittsburgh, stated that the one in eight proportion was equivalent to the share of lung cancer among all cancer cases in the United States. He emphasized that the issue was neither rare nor minor.
Moore added that the estimates from the International Agency for Research on Cancer could be very conservative, meaning the actual proportion of cancer cases linked to infections was likely even higher. He noted that infections are a far more important factor in cancer development than most people realize, though the impact of any specific infection depends heavily on the geographic region.
Reductions in HIV treatment caused by the termination of activities by the United States Agency for International Development, known as USAID, will lead to an increase in infection-related cancers in sub-Saharan Africa, Moore noted. Conversely, he pointed out that expanding hepatitis B vaccination among newborns in Asian countries could significantly reduce liver cancer cases linked to the virus.
Expert reactions on global cancer estimates
Karl Munger, a professor in the department of developmental, molecular and chemical biology at Tufts University, said the agency's estimate turned out to be lower than he had expected. He noted that other studies had suggested infections cause 15 to 20 percent of all cancer cases worldwide, while the proportion in the United States and other high-income countries remains significantly lower.
Munger stressed that the findings are important because infection often remains an underestimated and insufficiently recognized cause of cancer. He highlighted that despite this lack of recognition, many cancers linked to infectious agents can be prevented.
Dr Shan-Lu Liu, co-director of the viruses and emerging pathogens research program at The Ohio State University, described the study findings as both striking and encouraging. He explained that it was encouraging because many of these cancers can potentially be prevented through vaccination, infection control, screening, and medical treatment.
Liu added that the pronounced geographical variations in cancer rates demonstrate that the problem is closely tied to global health inequality.
Five main pathogens driving cancer cases
The study identified five main infectious causes of cancer in 2024. These included the bacterium Helicobacter pylori, human papillomavirus, hepatitis B virus, Epstein-Barr virus, and hepatitis C virus.
Helicobacter pylori accounted for the highest number of cases, linked to approximately 760,000 cancers worldwide in a single year, primarily affecting the stomach. Helicobacter pylori is a widespread bacterial infection that colonizes the human stomach lining.
Human papillomavirus, or HPV, was linked to roughly 750,000 cancer cases. The virus was most commonly responsible for cancers of the cervix, anal canal, vulva, vagina, and penis, alongside several types of head and neck cancers.
Hepatitis B virus accounted for about 360,000 cases, the majority of which involved liver cancer. Epstein-Barr virus was connected to around 260,000 cases, predominantly nasopharyngeal cancer, certain types of stomach cancer, and Hodgkin lymphoma, a cancer of the lymphatic system.
Hepatitis C virus was linked to approximately 160,000 cases, with most of those cases also involving liver damage and liver cancer.
Geographic disparities in infection burden
The highest overall burden of infection-related cancers was recorded in East Asia, sub-Saharan Africa, Central and Eastern Europe, and Southeast Asia. Researchers noted that the specific drivers varied markedly depending on the location.
In East Asia, the proportion of cancers tied to Helicobacter pylori and hepatitis B virus was particularly significant. Sub-Saharan Africa recorded very high rates of cancers linked to HPV, alongside a substantial burden from HIV and Kaposi sarcoma-associated herpesvirus.
Researchers explained that differences between regions are likely driven by varying infection rates, differences in access to prevention and treatment, and broader social and economic conditions.
Biological mechanisms triggering tumor growth
Dr Gary Clifford, a scientist at the International Agency for Research on Cancer and lead author of the study, explained how infectious agents trigger malignant growth. He stated that many infections hijack cellular machinery that controls the normal cell cycle in order to replicate themselves.
At the same time, these infections can interfere with cellular mechanisms responsible for repairing damaged genes or destroying mutated cells. As a result, the risk increases that such altered cells will transform into cancerous tumors.
Liu noted that other biological mechanisms also contribute to cancer, including chronic inflammation and repeated tissue damage. These processes can cause DNA damage and abnormal cell multiplication over time.
He explained that each main infection operates through a specific mechanism to promote cancer development, which explains why different pathogens are associated with distinct types of cancer.
Moore pointed out that at least five of seven infectious diseases involve viruses that carry oncogenes. When these viruses enter healthy cells, they can directly launch tumor development, leading to uncontrolled cell growth under conditions such as a weakened immune system.
Preventive measures and global barriers
Clifford emphasized that the study demonstrates a significant portion of cancer cases stems from known infections and is therefore preventable. He noted that infection-related cancers are particularly suitable for prevention compared to cancers linked to lifestyle factors because targeted vaccines, screening, and treatments exist.
Effective prevention tools already exist for many of these infections, according to the research team. These include vaccination against HPV and hepatitis B, testing and treatment for Helicobacter pylori, hepatitis B, hepatitis C, and HIV, as well as general measures to prevent infection transmission.
However, researchers noted that these preventive methods remain underused or inaccessible in many parts of the world, particularly in low- and middle-income countries. Obstacles include financial, social, and political barriers, such as limited access to vaccines, diagnostics, screening, and treatment, as well as social stigma surrounding conditions like HPV and HIV.
In several countries, prevention programs suffer from a lack of funding, insufficient political backing, and unequal access to medical services.
Public health priorities and future steps
Given the study findings, scientists from the agency urged policymakers and health systems to expand proven prevention programs. Key priorities include expanding vaccination against HPV and hepatitis B, alongside routine testing and treatment for Helicobacter pylori, hepatitis B, hepatitis C, and HIV.
They also called for measures to prevent transmission, such as safe injection practices, access to condoms, and HIV pre-exposure prophylaxis, commonly known as PrEP. Cervical cancer screening remains another vital preventive tool.
Liu stated that public health authorities must expand vaccination programs and make long-term infection testing and treatment more affordable. He called for stronger cancer screening among high-risk groups and better healthcare access in developing nations where the burden of infection-related cancer is highest.
Cognitive benefits of recreational reading
In separate health findings, researchers noted that reading for pleasure in spare time offers significant mental health and cognitive benefits. Choosing to read independently, rather than for work or study, reduces stress levels, improves mood, strengthens social bonds, and lowers the risk of cognitive decline in later life.
Scientists found that adults who read regularly maintain lower stress levels overall. In one survey, just six minutes of reading was linked to a reduction in stress, with more respondents reporting that they turn to books for comfort than to a hot bath.
