An estimated 2.3 million new cancer cases worldwide in 2024, representing approximately 12% of the global total, are attributable to infections. This significant finding comes from a recent analysis by the International Agency for Research on Cancer (IARC), a specialized cancer research agency of the World Health Organization (WHO).
While factors like smoking, alcohol, unhealthy diets, and environmental exposures are commonly associated with cancer, infections caused by specific bacteria and viruses contribute substantially to the global cancer burden. The IARC's findings, published in The Lancet Oncology, pinpoint five major infectious agents responsible for the vast majority of these cases.
How Infections Trigger Cancer
It's important to note that an infection does not automatically lead to cancer; most infected individuals will not develop the disease. However, persistent infections can initiate biological changes that heighten cancer risk. Some infections induce long-term inflammation, damaging cells and increasing the likelihood of cancerous mutations. Others interfere with normal cell growth regulation or enable abnormal cells to survive and multiply unchecked.
For example, chronic hepatitis B and C infections can progressively damage the liver, potentially leading to cirrhosis and liver cancer. Certain high-risk human papillomavirus (HPV) types can cause persistent cellular changes that eventually progress to cancer. Similarly, Helicobacter pylori can cause prolonged inflammation of the stomach lining, increasing the risk of stomach cancer.
The Five Key Infection-Related Cancer Agents
The IARC analysis identified these five agents as the primary drivers of infection-related cancers globally:
- Helicobacter pylori (H. pylori): This bacterium colonizes the stomach lining and is the leading infectious cause of cancer, accounting for an estimated 760,000 cases worldwide in 2024 (about 4% of all new cancers). Persistent infection can cause chronic gastritis, increasing the risk of stomach cancer and certain non-Hodgkin lymphomas. H. pylori infection can be diagnosed and treated with antibiotics, which can significantly reduce stomach cancer incidence.
- Human Papillomavirus (HPV): Transmitted primarily through intimate contact, HPV was linked to approximately 750,000 cancer cases in 2024 (around 4% of all new cancers). High-risk HPV types are responsible for nearly all cervical cancers, as well as some cancers of the anus, penis, vagina, vulva, and throat. HPV vaccination is highly effective in preventing these cancers, and screening remains a crucial intervention.
- Hepatitis B Virus (HBV): Infecting the liver, chronic HBV can lead to liver inflammation, cirrhosis, and liver cancer. HBV was associated with an estimated 360,000 cancer cases globally in 2024 (about 2% of new cancers). Vaccination is the primary preventive measure, with the WHO recommending infant vaccination within 24 hours of birth. Antiviral treatments can manage chronic HBV.
- Epstein-Barr Virus (EBV): A member of the herpesvirus family, EBV infects about 95% of people worldwide, often asymptomatically. It was linked to an estimated 260,000 cancer cases in 2024, including Burkitt lymphoma, Hodgkin lymphoma, nasopharyngeal cancer, and some stomach cancers. While no licensed vaccine exists yet, candidates are under development.
- Hepatitis C Virus (HCV): Primarily affecting the liver, chronic HCV infection can cause liver damage, cirrhosis, and liver cancer. HCV was responsible for around 160,000 cancer cases worldwide in 2024. There is no vaccine for HCV, but direct-acting antiviral medicines can cure over 95% of infections, substantially reducing liver cancer risk.
Global Disparities in Cancer Burden
The risk of infection-related cancer is not evenly distributed globally. The IARC analysis found that a staggering 77% of these attributable cancer cases in 2024 occurred in low- and middle-income countries. Eastern Asia recorded the highest number of cases, primarily driven by H. pylori and hepatitis B, accounting for about 42% of the global total.
Sub-Saharan Africa, however, had the highest proportion of cancers linked to infections, with roughly one in four new cancer cases in the region being infection-related, largely due to HPV.
These findings underscore a critical public health opportunity: vaccination, screening programs, early diagnosis, and effective treatments can prevent or significantly reduce the risk of many infection-related cancers. However, equitable access to these life-saving interventions remains a considerable challenge across different countries.