Around 12% of the world’s total cancer cases in 2024 were likely caused by an infection, according to new research from the World Health Organization (WHO).

The study, published today in The Lancet Oncology, analysed the frequency and causes of different cancers, specifically examining the role of infections.

It linked 2.3 million new cancer cases to an infection. Most were caused by just five pathogens: Helicobacter pylori (4%), human papillomavirus, or HPV (4%), hepatitis B (2%), Epstein-Barr virus (1%) and hepatitis C (under 1%). These infections can cause more than 20 different types of cancer, including stomach, liver, blood and cervical cancers.

So, how can an infection cause cancer? And does this mean these cancers are preventable?

Did we already know about this link?

Some of the study authors have been researching this field for around thirty years. Their previous work investigated cancer cases caused by infections in 1990, 2002, 2008, 2012, and 2018.

The proportion of cancer cases caused by infections may appear to have dropped during those years (from a high of 18% in 2002), but the authors stress these comparisons cannot really be made confidently, as the sources and quality of the data have changed over time.

In fact, the latest study wasn’t trying to compare between the years. Instead, it aims to highlight where controlling and preventing infections can help to........

© The Conversation