October 5, 2026, 5:54 p.m. ET
Millions of cancer cases worldwide, or about 1 in 8, have an underlying cause that is not only treatable but preventable, according to a new study.
The answer lies in infections, according to a study published this month in The Lancet Oncology, including two of the most common infections in the United States. According to the authors, about 12% of new cancer cases reported worldwide in 2024 could be attributed to just 12 infections, meaning that about 2.3 million cancers worldwide could have been prevented.
Five of these infections accounted for more than 2.2 million of the 2.3 million infection-attributable cancer cases recorded in the study, and two – common H. pylori stomach infection and sexually transmitted HPV – accounted for about 1.5 million.
The good news? According to researchers, we already know how to stop and treat these infections. The bad news? In some countries this does not happen.
Top five infections associated with cancer, study finds
- Helicobacter pylori (aka H. pylori): A common stomach infection that can cause stomach pain, bloating, gas, and similar symptoms. More than half of the world’s population could have an H. pylori infection at some point in their life, according to the Mayo Clinic. It is most associated with gastric cancers, according to the study (around 760,000 cases, or 4% of new cancer diagnoses worldwide).
- HPV (human papilloma virus): A common infection with more than 100 types, HPV is the most common sexually transmitted viral infection in the United States, infecting approximately 14 million people annually, according to the Cleveland Clinic. Certain strains are high-risk factors for certain cancers, including those of the cervix, vagina and vulva. It was most associated with cervical cancer in the study (about 750,000, or 4%, of new cases). There is a vaccine that is ideally given before a person becomes sexually active.
- Hepatitis B (HBV): A vaccine-preventable liver infection, often asymptomatic, that can range from a short acute illness to a serious chronic infection, according to the CDC. Acute infections are more common in people aged 40 to 59. In the study, they were mainly associated with liver cancers (around 360,000, or 2%, of new cases).
- Epstein-Barr virus (EBV): A very common viral infection and type of herpesvirus that often does not cause symptoms and mainly affects children, adolescents and young adults. According to the Cleveland Clinic, up to 95% of adults become infected with EBV during their lifetime. In the study, it was most associated with head and neck cancers (about 260,000, or 1%, of new cases).
- Hepatitis C (HCV): A viral infection that causes inflammation of the liver and can lead to serious damage. Like hepatitis B, it can cause a short-term acute illness or a long-term chronic illness. It is often asymptomatic; Experts estimate that more than 2 million people have chronic hepatitis C in the United States, according to the Cleveland Clinic. In the study, it was most associated with liver cancers (around 160,000, or just under 1%, of new cases).
Other infections identified as being linked to cancer include HIV, Kaposi’s sarcoma-associated herpesvirus, Schistosoma haematobium (a blood parasite common in Africa and the Middle East), human T-cell lymphotropic virus type 1, Opisthorchis viverrini (a liver parasite found in Southeast Asia), Clonorchis sinensis (another liver parasite from Southeast Asia), and Merkel cell polyomavirus (a virus known primarily to cause cancer, called an oncovirus).
What to keep in mind
The study does not track each individual cancer case. Instead, it uses global cancer data and previous research to estimate how many cancers are linked to infections. The authors say these figures are the best estimates available, but gaps in cancer reporting in some parts of the world mean the totals are not accurate. Additionally, it only considers infections that are already known to be associated with cancer – there could be others for which there is not yet enough evidence to link the two.
Cancer registries are less complete in some regions, particularly low-income countries, making it difficult to measure the true global burden of infection-related cancers. This is particularly important for this study because it found that 77% of infection-related cancer cases occurred in low- and middle-income countries. East Asia, sub-Saharan Africa and Southeast Asia were among the regions with the highest cancer burden.
It’s important to remember that although 12% of all cancer cases worldwide is a significant number, most cancers are not caused by infection, at least not according to what scientists currently know.
When preventing infections could mean preventing cancer
Although infection may not be the leading cause of all cancers nationwide, it accounts for a disproportionate number of cases in certain types of cancer, such as cervical cancer. The study found that the vast majority of cases of cervical cancer can be attributed to HPV, for example.
The researchers also noted that this means that several cancers could be prevented with tools we already have but are not being used. In these cases, the fight against infections, which is already a well-established science, could lead to the fight against cancer.
Although the authors note that more research is needed, particularly for some still-explored infection-cancer relationships, such as Epstein-Barr, we already have proven methods for addressing some risks. Areas with the highest cancer burden do not have as easy access to resources used to track, prevent and control infection, they found.
- HPV vaccination is a major prevention tool, according to the authors of the study. CDC data shows that it can be very effective in preventing both infections and related cancers.
- In the 12 years since the Gardasil vaccine was introduced in the United States, infections of the four HPV types it targets declined by 88% among women ages 14 to 19 and by 81% among women ages 20 to 24.
- Cervical precancer rates among screened women fell 50% among 18- to 20-year-olds and 36% among 21- to 24-year-olds in the six years after Gardasil hit the market, and cervical lesions from vaccine-prevented HPV types fell 40% among vaccinated women after the vaccines were introduced.
- Hepatitis B vaccination is also available and is recommended by the CDC for all infants, children, and adults ages 19 to 59, as well as adults 60 and older at high risk of infection. Vaccination reduces the risk of liver cancer linked to HBV infection. Every adult should be tested at least once in their life for hepatitis B, says the CDC, and people at higher risk (people of certain ages, races, family history, and with certain conditions) should be tested regularly.
- More frequent testing and treatment for H. pyloriwhich may include stool, breath or endoscope examinations and antibiotics, can reduce its spread and prevalence and therefore its likelihood of contributing to cancer.
- Testing and treatment for hepatitis B, hepatitis C and HIVlike H. pylori mentioned above, can not only help reduce transmission, but also prevent infections from becoming chronic, leading to a higher risk of cancer.
- Safer injection practices, condom use, PrEP to use and making the tools needed for these practices more available can help stop the transmission of HIV, hepatitis B and hepatitis C, thereby reducing the associated cancer burden.
- Screening and treatment of precancerous lesionsespecially in cases of HPV-related cervical and anal cancer, may contribute to early diagnosis and better cancer-related outcomes.
Gn Health
