Human papillomavirus (HPV) is a group of more than 100 different types of related viruses. Certain types of papillomaviruses can cause warts (papillomas), which are non-cancerous (benign). They can occur on different parts of the body, such as the hands, feet, genitals (such as the penis or vulva) or anus.
Types of HPV
HPVs are often given a number to identify them. The different types of HPVs are grouped into low-risk and high-risk types based on the degree of risk of developing cancer after infection. Low-risk HPV types are rarely associated with cancer, whereas high-risk HPV types can cause certain cancers.
The most common low-risk types are HPV-6 and HPV-11, although there are others.
About 90% of genital warts (condylomata acuminata) are caused by low-risk HPV-6 and HPV-11. Genital warts do not turn into cancer.
HPV-6 and HPV-11 can also cause an uncommon condition called recurrent respiratory (laryngeal) papillomatosis. This condition causes benign tumours to grow inside the larynx or the respiratory tract.
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HPV is the most common sexually transmitted infection. More than 40 types of HPV are transmitted through sexual intercourse, genital skin-to-skin contact and oral sex. They can infect the genital areas of men and women, including the penis, vulva, vagina, cervix, rectum and anus. They can also infect the mouth (oral cavity) and throat (oropharynx).
Infection with HPV usually occurs soon after the onset of sexual activity. About 75% of sexually active males and females will have an HPV infection at some point in their lifetime. The incidence of HPV infection tends to peak in adolescents and young adults and slowly declines with age. In fact, females under the age of 20 generally have the highest rates of HPV infection.
- Certain types of sexual behaviour increase a person’s risk of HPV infection, such as having many sexual partners and having unprotected sex.
- People with a weakened immune system have an increased risk of HPV infection.
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).
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Most people never know they have an HPV infection because many types of HPV don’t cause any symptoms. This makes it easy to pass along HPV without even knowing you have it.
Some types of HPV cause genital warts. External genital warts may look like a small cauliflower, may be flat or may be too small to be seen.
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HPV and cancer
The body’s immune system usually gets rid of an HPV infection on its own. Most HPV infections (about 70%) go away without any treatment within 1–2 years. Persistent infection with high-risk HPV types over many years can cause precancerous changes and cancer. However, not everyone with an HPV infection will develop cancer. Only a small number of infections with high-risk HPV will progress to cancer.
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 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
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Testing for an HPV infection can be done on a sample of cells, such as cells from the cervix. In this case, the cells are collected in basically the same way as a Pap test and HPV testing can be done on the same sample taken during a Pap test. The HPV test looks at the DNA in the cells to identify the type of HPV. HPV testing is not part of regular cervical cancer screening, but it is done in certain situations. It helps identify women who have cervical abnormalities or are likely to have precancerous changes that could develop into cervical cancer.
The HPV test does not replace a Pap test. Pap testing is still the main tool for detecting cervical cancer. However, research has shown that HPV testing is more accurate than the Pap test in detecting precancerous changes in the cervix. While this test could be an important part of cervical cancer screening in the future, its role for screening in the general population is not yet well defined. Research so far tells us that it works better for some groups of women than others.
- Studies have shown that HPV testing as a cervical cancer screening tool is most effective for women 30 years of age and older.
- The HPV test is usually not appropriate for woman younger than 30 because temporary HPV infections are very common in this age group. These infections are unlikely to result in abnormal cervical changes that could lead to cancer.
The HPV test is available in Canada, but not in all provinces or territories. Where it is available, the HPV test is usually used only for women 30 years of age and older as a follow-up to an abnormal Pap test result. Research is being done to see how HPV testing can best be included in cervical screening programs. HPV causes cervical cancer and HPV DNA is detected in virtually all cervical cancers, so researchers are studying new screening techniques based on HPV with the hope of improving detection and prevention of precancerous conditions of the cervix and cervical cancer. The impact that HPV vaccination will have on cervical cancer screening is also being looked at.
HPV testing in men
Currently in Canada there is no approved DNA test for HPV in men. However, genital warts associated with an HPV infection can be found during a physical examination by a healthcare professional.
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There is no treatment for HPV infection, but there are treatments for the health problems caused by HPV, such as genital or anal warts, precancerous conditions and cancer. Treatment depends on the type of changes in the cells or the stage of cancer.
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Reducing your risk
You can reduce your risk of being exposed to HPV. The only sure way to prevent HPV infection is to completely avoid any genital contact with another person. If you are young, delay having sex. If you are sexually active, you can reduce your risk by:
- limiting the number of sexual partners
- being in a monogamous relationship with someone who hasn’t had many sexual partners
- using a condom
- Using a condom can reduce the risk of HPV infection if it is put on before skin-to-skin sexual contact.
- Areas not covered by the condom still allow some skin-to-skin contact during sex. So using a condom will reduce, but not eliminate, the risk of HPV infection.
You can also reduce your risk of HPV infection by getting vaccinated against HPV.
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