A study in The Lancet Oncology tied 2.3 million new cancer cases in 2024 to infections. Cancer-causing infections therefore account for roughly one in eight cases, or about 12 percent of the total. Researchers said vaccination, testing and treatment could prevent many of these cases.

Five infections caused most of the burden. Helicobacter pylori led the list with about 760,000 cases, or 4 percent of the global total. Human papillomavirus (HPV) followed with about 750,000 cases.

Hepatitis B added 360,000 cases, while Epstein-Barr virus (EBV) accounted for 260,000. Finally, hepatitis C caused another 160,000 cases. David Greenberg of Hackensack Meridian Jersey Shore University Medical Center said the findings show better infection control could prevent a large part of the global cancer burden.

HPV can cause cervical, anal, genital, mouth and throat cancers. A vaccine prevents it and works best before a person becomes sexually active. Meanwhile, chronic hepatitis B and C can damage the liver and lead to cirrhosis and liver cancer.

A vaccine and antiviral medicines can manage hepatitis B, although treatment usually does not cure it. However, no vaccine exists for hepatitis C. Still, direct-acting antiviral medicines cure more than 90 percent of patients within two or three months.

H. pylori is the most common bacterial cause of cancer. It spreads through saliva and contaminated food or water, and most infections begin in childhood. Doctors can treat it with antibiotics and medicines that reduce stomach acid.

EBV also stays in the body and can contribute to nasopharyngeal cancer, some lymphomas and stomach cancer. More than 90 percent of adults show signs of past EBV infection. Moreover, no vaccine or approved antiviral treatment exists for it yet.

The study also included HIV, a known cancer-causing virus. People with advanced HIV can develop Kaposi sarcoma and non-Hodgkin lymphoma. Even people with well-controlled HIV still face a higher risk of several cancers.

HHV-8 usually causes no illness in healthy people but can cause tumors when immunity is weak. Other infections in the study include human T-cell lymphotropic virus, Merkel cell polyomavirus, Schistosoma haematobium and two liver flukes. These can cause bladder, liver and bile duct cancer.

More than three-quarters of these cases occurred in low- and middle-income countries. East Asia had the largest number, with around 990,000 cases, or 42 percent of the global total. Rates also ran higher than average in sub-Saharan Africa, Central and Eastern Europe, and Southeast Asia.

Researchers highlighted HPV and hepatitis B vaccination, along with testing and treatment for HIV, H. pylori and hepatitis. They also pointed to safer injection practices, condom access, HIV PrEP and cervical screening. Furthermore, they called for more investment in new prevention tools, especially for EBV.

Overall, cancer-causing infections remain a major but preventable part of the global cancer burden.