When individuals think about cancer prevention, they typically think of stopping smoking, limiting alcohol consumption, or eating healthier. However, a new global investigation by the World Health Organization (WHO) and its cancer research arm, the International Agency for Research on Cancer (IARC), indicates a lesser-known and frequently misinterpreted risk: infections. 

The analysis, released ahead of World Cancer Day on February 4, shows that infections are now the world's second greatest preventable cause of cancer, accounting for almost 7.1 million new cases in 2022—roughly one in every ten cancers. 

What did the study uncover, and why does it matter? 

The WHO-IARC investigation, which used data from 185 countries and 36 cancer types, evaluated 30 modifiable risk variables ranging from smoking and alcohol use to air pollution and physical inactivity. For the first time, a global estimate included nine cancer-causing diseases, including human papillomavirus (HPV), hepatitis B virus, and Helicobacter pylori. 

According to the data, 37% of all new cancer cases worldwide were caused by factors that could have been avoided. Tobacco remained the leading cause, accounting for 15% of new malignancies, closely followed by infections (10%) and alcohol (3%). 

"This is the first global analysis to show how much cancer risk comes from causes we can prevent," said Dr André Ilbawi, WHO Team Lead for Cancer Control and research author. "By examining patterns across countries and population groups, we can provide governments and individuals with more specific information to help prevent many cancer cases before they start." 

How might infections cause cancer? 

In contrast to smoking and nutrition, infections work silently and gradually. A virus or bacterium may enter the body years earlier, causing long-term inflammation or cell damage before eventually contributing to cancer. Helicobacter pylori, a common stomach bacterium acquired in childhood, is the leading cause of stomach cancer globally. Similarly, HPV infection causes almost all cases of cervical cancer, whereas hepatitis B is a primary cause of liver cancer. 

This explains why three malignancies—lung, stomach, and cervical—represent roughly half of all avoidable cancers worldwide. 

Who is the most affected? 

The burden of avoidable cancers is not evenly distributed. Among men, 45% of new cancer cases were due to avoidable causes, with smoking accounting for 23%. The percentage was lower for women, at 30%, but infections emerged as the biggest preventable cause, accounting for 11% of new cancer cases worldwide. 

Regional distinctions were also significant. Preventable cancer rates among women ranged from 24% in North Africa and West Asia to 38% in Sub-Saharan Africa, indicating disparities in immunisation, screening, and access to basic healthcare. 

"This landmark study is a comprehensive assessment of preventable cancer worldwide," stated Dr Isabelle Soerjomataram, Deputy Head of the IARC Cancer Surveillance Unit and the study's senior author. "Addressing these preventable causes represents one of the most powerful opportunities to reduce the global cancer burden." 

What can really be done? 

The report moves the cancer debate away from human willpower and toward public health action. Vaccines against HPV and hepatitis B, H. pylori testing and treatment, better air, safer workplaces, and stronger tobacco control could all help to avoid millions of cancer cases. 

For individuals, the report means that cancer prevention involves not just lifestyle choices but also timely immunisation, basic diagnostics, and early treatment—all of which are straightforward procedures that do not necessitate a major redesign of daily life. 

The basic message is clear: many cancers begin long before diagnosis, but they also begin at a time when prevention remains possible. Investing in infection control and prevention now could save millions of families from receiving cancer diagnoses tomorrow.