While there are many factors that put women at risk of developing cervical cancer, almost all cervical cancers are caused by the human papillomavirus (HPV), the same virus responsible for genital warts. There are over 100 different types of HPV. However, only some types are associated with cervical cancer. These are called high-risk types. High-risk HPV types include:

• HPV 16
• HPV 18
• HPV 31
• HPV 33
• HPV 45

According to the American Cancer Society Trusted Source (ACS), about two-thirds of all cervical cancers are caused by HPV 16 and 18. However, both types can be prevented with vaccination. Also, not all infections from these HPV types cause cervical cancer. Most women "clear" themselves of HPV infections within two years. Infections that last more than a few years are called persistent infections. These are the infections that are most likely to cause cancer. It is not understood why some women treat HPV infections while others do not.

How common is HPV?

HPV is extremely common. According to the US Centers for Disease Control and Prevention (CDC), more than half of sexually active adults become infected during their lifetime. Fortunately, the two types of HPV responsible for most cases of cervical cancer can be prevented by vaccination. The two types responsible for most cases of genital warts can also be prevented by vaccination. However, vaccination is most effective when given before the start of sexual activity.

Safe sex and cervical cancer

HPV is transmitted during sexual intercourse. It can be spread through vaginal sex, oral sex and anal sex. Safe sexual practices can reduce the risk of transmission. Condoms should be used for vaginal and anal sex. Condoms can also reduce the risk of transmission during oral sex. However, condoms cannot completely prevent HPV. The virus is also transmitted by skin-to-skin contact. Sexually transmitted HPV has been linked to:

• cervical cancer
• anal cancer
• cancer of the vulva
• cancer of the throat

Safe sex reduces the risk of HPV-related cancers.

Risk factors for cervical cancer

Certain genetic and lifestyle factors can increase a woman's risk of contracting HPV, which can lead to cervical cancer. These include:

• first contact at an early age
• large number of sexual partners
• a history of other sexually transmitted infections, such as chlamydia or gonorrhoea
• sex with a man whose partner had an HPV/cervical cancer infection

It is important to note that other biological factors also influence HPV infection. In young women, the cervix is more susceptible to infection. Smoking increases the likelihood that HPV infection will turn into cancer. Immunodeficiency (weak immune system) also makes it harder for the body to eliminate an HPV infection. However, not all HPV infections lead to cervical cancer. Although the exact cause is unknown, factors that may increase the risk for cervical cancer include:

• more than 3 full-term pregnancies or 1 full-term pregnancy before the age of 17
• family history of cervical cancer
• long-term use (more than 5 years) of oral contraceptives
• chlamydia infection