THAT'S THE WHY:When you think of illnesses caused by viruses, conditions such as colds, flu, hepatitis and Aids might spring to mind.

But viruses can be linked to cancer too, and in the case of cervical cancer, which is cancer in the cervix of the womb, the human papillomavirus (HPV) is a prime suspect.

In 2008, German virologist Harald zur Hausen scooped a share in a Nobel Prize for discovering that high-risk HPV types can be linked with cervical cancer, and today we can vaccinate against the types of HPV that are linked with about 70 per cent of cases.

But why can infection with a virus raise the risk of cancer further down the road? In the cases of HPV 16 and 18, which are the types of HPV most often linked to cervical cancer, infection can disable parts of the molecular machinery in human cells that normally protect against cancer developing.

In particular, the infecting virus produces “oncoproteins” called E5, E6 and E7, which affect various biochemical processes in the human host cells in a manner that raises the risk of those cells eventually “transforming” into cancerous cells.

“The HPV oncoproteins E5, E6 and E7 are the primary viral factors responsible for initiation and progression of cervical cancer, and they act largely by overcoming negative growth regulation by host cell proteins and by inducing genomic instability, a hallmark of HPV-associated cancers,” write the authors of a 2010 paper in Nature Reviews Cancer