Cancer of the cervix is caused by HPV infection, which is usually transmitted through sex. It occurs when cells on the cervix become abnormal and grow uncontrollably. Girls and women who are sexually active are most at risk. Early signs may include bleeding after sex or between periods. However, HPV infection often does not show signs for 10-15 years. Vaccination against HPV is available for girls aged 10 and can help prevent cervical cancer later in life.