This common virus is much more dangerous than previously thought, increasing the risk of developing cancer by five times.

A link between this virus and cancer had already been established, but the risk would be much greater than previously thought.

Tobacco, alcohol, unhealthy diet, lack of physical activity, genetics... We're all familiar with these widely proven causes of cancer. But others are less well known. For example, certain viruses can increase the risk of developing cancer. Among them: the Epstein-Barr virus (EBV). While little-known to the general public, it's "the most common and persistent human virus. It infects approximately 95% of the world's population with lifelong, asymptomatic infection." It can also cause mononucleosis... or worse, cancer.

This virus from the herpes family was in fact classified as "carcinogenic to humans" by the International Agency for Research on Cancer (IARC), which is part of the WHO, in 1997. It has already been linked to certain cancers, including lymphomas, carcinomas, and stomach cancers. But " although the association of EBV infection with certain types of cancer, such as lymphomas and nasopharyngeal carcinoma, is well established, there is less data on the risk of cancer in general ," explained Dr. Zisis Kozlakidis, co-author of a new study conducted by the IARC and published in the journal Nature in early July 2025, in a press release.

To better understand this risk, researchers monitored the health of nearly 75,000 people in China for a decade. They observed that people who had antibodies to - and therefore had been infected with - the Epstein-Barr virus " were nearly 5 times more likely to develop cancer " than those who did not have antibodies to the virus. For cancers already associated with the virus, the risk was multiplied by 3.2 for lymphoma and even by... 26 for nasopharyngeal carcinoma!

The researchers also discovered a previously unknown link with certain types of cancer. People who had Epstein-Barr virus antibodies had a 1.76 times greater risk of developing lung cancer and a 1.7 times greater risk of developing liver cancer.

According to the researchers, nearly 8% of cancers in southern China—where the study was conducted—could be "attributed " to the Epstein-Barr virus. This is four times higher than previously estimated. Further studies are needed to confirm and assess this risk in other parts of the world.