1 in 8 Cancer Cases Worldwide Linked to Infections: Which Viruses and Bacteria Increase the Risk?

Around one in eight cancer cases worldwide may be linked to infections, highlighting the importance of vaccination, screening and timely treatment in cancer prevention. A new global analysis estimates that approximately 2.3 million new cancer cases in 2024 were attributable to infections caused by viruses, bacteria, and parasites.

The study published in The Lancet Oncology examined the contribution of cancer-causing infectious agents across countries and found that many infection-related cancers could be prevented or reduced through existing healthcare measures.

According to researchers from the International Agency for Research on Cancer (IARC), infection control is an important but often overlooked part of cancer prevention.

Which Infections Are Linked to Cancer?

The analysis identified several infectious agents responsible for a significant proportion of infection-related cancer cases worldwide.

Helicobacter pylori (H. pylori), a bacterium that infects the stomach lining, was linked to approximately 760,000 cancer cases. It is associated with stomach cancer and certain types of non-Hodgkin lymphoma.

Human papillomavirus (HPV) accounted for around 750,000 cases. Persistent infection with high-risk HPV types is the leading cause of cervical cancer and can also cause cancers of the anus, penis, vulva, vagina, and oropharynx.

Hepatitis B virus (HBV) was associated with approximately 360,000 cases, while Epstein-Barr virus (EBV) was linked to around 260,000 cases. Hepatitis B can cause liver cancer, while EBV is associated with certain lymphomas and other cancers, including some stomach cancers.

Hepatitis C virus (HCV) was linked to approximately 160,000 cases, primarily through its association with liver cancer.

Together, these findings show how certain persistent infections can contribute to cancer development over time.

Also Read: Everyday Habits That May Increase Women’s Risk of Gynaecological Cancers

How Can Infections Lead to Cancer?

Not every infection causes cancer, and most people who experience these infections will not necessarily develop the disease.

However, certain pathogens can increase cancer risk by causing long-term inflammation, damaging cells, or interfering with normal cell growth. Persistent infections may also allow abnormal cells to survive and multiply, increasing the likelihood of cancer developing over time.

For example, chronic hepatitis B and C infections can damage the liver, leading to scarring and an increased risk of liver cancer. Persistent infection with high-risk HPV types can cause changes in cervical cells that may eventually become cancerous if left undetected and untreated.

The risk depends on the infectious agent, the duration of infection, the person's immune response, and other factors.

Can Infection-Related Cancers Be Prevented?

Researchers emphasise that many infection-related cancers can be prevented or their risk reduced through established healthcare measures.

Vaccination is an important preventive tool. HPV vaccination helps protect against the virus types responsible for most cervical cancers and several other cancers. Hepatitis B vaccination can prevent infection and reduce the risk of liver cancer.

Screening and timely treatment are also important. Cervical screening can detect precancerous changes before they develop into cancer. Testing and appropriate treatment for hepatitis B and C can help reduce complications, while identifying and treating H. pylori infection when medically indicated may lower the risk of certain stomach cancers.

Safe injection practices, condom use, and measures to prevent HIV transmission can further reduce the risk of relevant infections.

Also Read: HIV Injections May Work Better Than Daily Tablets for Young People, Lancet Study Finds

Why Do These Findings Matter?

The burden of infection-related cancer is not evenly distributed across the world. The study found that eastern Asia accounted for approximately 42% of the global total, while several other regions also recorded rates above the global average.

Limited access to vaccination, screening, diagnostic services and treatment can make prevention more difficult, particularly in low- and middle-income countries.

The findings underline that cancer prevention involves more than lifestyle changes and early diagnosis. Controlling cancer-causing infections through vaccination, testing and appropriate treatment could help prevent a substantial number of future cases.