Human papillomavirus (HPV) is a group of more than 100 different types of viruses. More than 40 types of HPV are transmitted through sexual intercourse, genital skin-to-skin contact and oral sex. These types can infect the genital areas of both men and women, including the penis, anus, vulva, vagina and cervix, as well as the oral cavity and throat (the oropharynx).
Infection with HPV usually occurs soon after the onset of sexual activity. It is estimated that about 75% of sexually active men and women will have at least 1 HPV infection in their lifetime. Young women 20-24 years old generally have the highest rates of cancer-causing HPV infection (24%). Infection rates decrease as women get older because most develop immunity against the virus. Most HPV infections come and go over the course of a few years. This makes it hard to know exactly when or from whom a person got the virus.
There are many different types of HPV and becoming immune to one type does not protect you from getting other types. It is possible to have more than one type of HPV infection at a time. It is also possible that your immune system’s memory of a type of HPV can fade over time, so that you may get another infection from the same HPV type later (reactivation of a previous infection).
Sexually transmitted HPV are either high-risk or low-risk.
Infection with high-risk HPV can cause the cells in a woman’s cervix to change or become abnormal. These precancerous changes can lead to cervical cancer. HPV 16 and 18 are the most common high-risk types and are responsible for 70% of cervical cancers.
Infection with high-risk HPV, especially HPV 16, is also linked to cancers of the penis, anus, vulva, vagina, as well as the oral cavity and throat. Not all cases of these rare cancers are linked to having an HPV infection.
Infection with low-risk HPV doesn’t cause precancerous changes in the cervix and doesn’t increase a woman’s risk of cervical cancer. But low-risk types of HPV can cause genital warts. The two low-risk types of HPV that are responsible for 90% of genital warts are HPV 6 and 11.
HPV 11 can also cause recurrent laryngeal papillomatosis (tumours that grow inside the larynx, vocal cords or respiratory tract). This is a rare condition that can affect children, adolescents, and young adults.
Symptoms of HPV infection
Most people will never know they have been infected because HPV usually doesn’t cause any symptoms (unless you are infected with the type that causes genital warts). This means you can get HPV and pass it along without ever knowing it. While an HPV infection can’t be treated, what it causes can.
- Precancerous cervical changes can develop if there is a persistent or continuous high-risk HPV infection. Precancerous cervical changes and cervical cancer can be treated.
- Genital warts caused by low-risk types of HPV can appear weeks or months after skin-to-skin sexual contact with an infected person. There are treatments for genital warts
HPV and cervical cancer
Most men and women who are sexually active will have an HPV infection at some point over their lifetime. In most cases, high-risk type HPV infections go away on their own within a few months. For most women, the virus will no longer be detected after 2 years. Sometimes the HPV infection does not go away. This can lead to changes in the cells of the cervix. These changes can develop into cervical cancer if they are not detected early and treated.
HPV infection is a well-established cause of cervical cancer. HPV is present in nearly all cervical cancers. HPV-16 and HPV-18 cause about 70% of cervical cancers. Other high-risk HPVs also cause cervical cancer, including HPV types 31, 33, 35, 39, 45, 51, 52, 56, 58 and 59.
HPV and other cancers
HPV infection can cause anal, vaginal, vulvar, penile and some oral cavity and oropharyngeal cancers. Most of these cancers are attributed to high-risk HPV-16 and HPV-18. HPV-33 has also been found in cancer of the anus and vulva. HPV infection is associated with about:
- 80–90% of anal cancers
- 40% of vaginal and vulvar cancers
- 40–50% of penile cancers
- 25–35% of oral cavity and oropharyngeal cancers
Preventing HPV infection
The only sure way to prevent HPV infection is to completely avoid any genital contact with another individual. If you are sexually active, you can reduce your risk by:
- having as few sexual partners as possible
- being in a monogamous relationship with someone who hasn’t had a lot of sexual partners
- using condoms
Using a condom can reduce HPV infection if it is put on before skin-to-skin sexual contact. However, areas not covered by a condom still allow some skin-to-skin contact during sexual activity. So using them will reduce, but not eliminate, the risk of HPV infection.
Two vaccines that protect against HPV 16 and 18 infections are available in Canada.
Find out more about HPV vaccines.