A study by the International Agency for Research on Cancer (IARC), part of the World Health Organization, published in The Lancet Oncology, found that about one in eight cancers worldwide is caused by infections. These cancers are largely preventable through measures like vaccination and treatment. In 2024, approximately 2.3 million cancer cases were attributed to viruses, bacteria, or parasites. Helicobacter pylori, human papillomavirus (HPV), and hepatitis viruses are among the main infectious agents identified. The findings update previous research from 2018, which showed new links between infections and cancer. For example, the Epstein-Barr virus, known for causing certain lymphomas and nasopharyngeal cancers, is now also linked to stomach cancer and other rare lymphomas. In 2024, this virus was responsible for about 260,000 cancer cases. Helicobacter pylori remains the leading cause, with around 760,000 cases, followed by HPV (750,000 cases), hepatitis B (360,000), and hepatitis C (160,000). The study also highlights significant regional differences. Infectious cancers mainly affect people in low-income countries with limited access to prevention and treatment. East Asia accounts for 42 percent of these cases, and sub-Saharan Africa for 28.5 percent. Dr. Anna Giuliano, an epidemiologist from the Moffitt Cancer Center, emphasizes that infectious agents can cause cancer and that solutions exist. She mentions the importance of screening and treating hepatitis C, vaccinating against hepatitis B and HPV, and using antibiotics for Helicobacter pylori infections. Globally, about 20 million new cancer cases are diagnosed each year. In 2022, lung cancer was the most common, with 2.5 million new cases, followed by breast cancer (2.3 million) and colorectal cancer (1.9 million). According to the IARC, about 2.3 million of the new cancer cases in 2024 were caused by infections, often preventable. These findings were published in The Lancet Oncology. Researchers estimated that twelve infectious agents, including viruses, bacteria, and parasites, were responsible for new cancer cases in 2024. Helicobacter pylori caused around 760,000 cases, followed by HPV (750,000 cases), hepatitis B (360,000), Epstein-Barr virus (260,000), and hepatitis C (160,000). Dr. Gary Clifford, a co-principal author of the study, noted that the understanding of infection-related cancers is evolving with new scientific discoveries. For example, the Epstein-Barr virus, which causes infectious mononucleosis, is also linked to certain cancers like lymphomas and stomach cancer. The study also highlighted geographical disparities. East Asia accounts for 42 percent of infectious origin cancers, largely due to Helicobacter pylori and hepatitis B. However, there are solutions, such as vaccines for HPV and hepatitis B, and treatments for HIV and Helicobacter pylori. Prevention methods include using condoms and screening for precancerous lesions in cervical and anal cancers. Breast cancer is now the most diagnosed cancer globally, surpassing lung and colorectal cancers. However, lung cancer remains the deadliest. About half of the world’s population is infected with Helicobacter pylori, which can cause stomach ulcers and sometimes gastric cancer. The Pasteur Institute spoke with Hilde De Reuse, head of the Helicobacter Pathogenesis unit, to learn more about this bacterium and the research being conducted in her laboratory.