One in three of us will get cancer at some stage in our lives. From the moment of diagnosis, the common cry is, 'why me?' We blame our genes, our environment and our lifestyle, but could we be overlooking another crucial cause of cancer?

In Australia, a mysterious cancer cluster has led to an unusual investigation. Sixteen women working in one workplace have developed breast cancer. The majority are young, none have a family history of the disease and no environmental cause has been found for the illness. A team of scientists has begun to investigate if the cause could be a virus. It is a controversial idea, with extraordinary implications.

Approximately 20 per cent of all cancers worldwide are caused by infections. Some scientists say it could be as high as 50-95 per cent . Across the planet, startling new evidence is emerging that links viruses and bacteria to an increasing number of cancers. And two Nobel prizes in the last five years mean the story of infections causing cancer cannot be ignored.