It’s been called one of the most significant cancer clusters in the world. Sixteen women in one workplace in Australia have developed breast cancer. Most are young; none have a family history of the disease. Experts declared the chances of this being a statistical fluke were “one in a million”. But despite an intense investigation no cause was found. Now a team of scientists will re-examine this medical mystery asking, could the cause be a virus? It’s not as bizarre a question as you might think. One in five cancers are caused by infections, according to the World Health Organization. The question is: could there be more?