(Human Papillomavirus Infection)
In this condition factsheet:
The Facts on HPV Infection
The human papillomavirus (HPV) is a virus that causes skin and mucous membrane (the moist lining of body cavities such as the mouth and nose that connect with the outside of the body) infections. It is passed from one person to another by skin-to-skin contact, including sexual contact.
There are more than 100 types of HPV that can affect different parts of the body. Some types of HPV can cause warts (such as genital or plantar warts) and others can cause cancer (such as cervical or anal cancer).
HPV infection is one of the most common sexually transmitted infections (STIs) in Canada and around the world. At least 70% of sexually active men and women will have at least one HPV infection in their lifetime, and approximately 3 to 9 million Canadians are infected with HPV.
The different HPV types are classified into low and high risk based on their association with cancer. "Low risk" types rarely cause cancer. "High risk" types have a greater likelihood of causing cancer but they do not necessarily lead to cancer. These various types can cause different conditions, including:
- skin warts: These infections are also known as common, plantar, or flat warts and are caused by low-risk types. The warts can appear on your arms, face, feet, hands, and legs. They can develop at any age but are most common in children.
- genital warts: HPV types 6 and 11 cause most cases of genital warts and are low-risk types.
- cervical dysplasia: HPV can cause lesions of abnormal cells called cervical dysplasia in a woman's cervix. These lesions are considered to be precancerous (they are not cancerous cells, but they may develop into cancer cells later). The HPV infection often resolves and clears on its own, but cervical dysplasia should be treated because it can lead to cervical cancer.
- cervical cancer: The high-risk HPV types 16 and 18 cause about 70% of all cervical cancers. Types 16 and 18 have also been linked to penile cancer and anal cancer.
HPV can cause infections and lesions in other areas of the body, such as in the upper respiratory tract.
The majority of HPV infections are generally harmless, though they can be embarrassing. However, the HPV infections that can lead to cervical cancer and other types of cancers are a concern.
Causes of HPV Infection
HPV enters the body, usually through a break in the skin, and then infects the cells in the layers of the skin. The virus then replicates or multiplies in the body. The time between first contracting HPV and the appearance of lesions can be weeks to months or even years. Many people don't even know they are infected with HPV.
HPV is transmitted by skin-to-skin contact. HPV infections that cause skin warts (e.g., plantar or common warts) can be acquired through a cut, but the risk of transmission is low. Walking barefoot in public areas such as the gym or pool can be a risk for infection with the types of HPV that cause plantar warts.
HPV infections that cause genital warts are very contagious and are usually contracted through sexual activity with an infected person. This includes kissing or touching the skin of the infected areas (e.g., scrotum, vagina, vulva, anus) and having intercourse. Although HPV is more likely to be transmitted when lesions or warts are visible, transmission is possible even without the presence of visible warts.
A mother with a genital HPV infection may also transmit the virus to the infant during labour.
The risk factors for HPV infection include:
- age: Children and young adults are most at risk for developing common warts and flat warts. Genital HPV infections usually occur in teenagers and young adults.
- number of sexual partners: The higher the number of sexual partners, the greater the risk of genital HPV infection.
- immune system: People who have a compromised immune system (e.g., HIV or AIDS, organ transplant recipient, or who are taking medication that suppresses the immune system) are at an increased risk of genital HPV infection.
Symptoms and Complications of HPV Infection
Most HPV infections go unnoticed because they don't cause any symptoms. The virus may have been contracted years ago and it can remain in the body for weeks, years, or even a lifetime without showing any symptoms of an infection.
For those who experience symptoms, the type of symptoms depends on the type of HPV infection.
- Common warts are painless, firm growths with a rough surface and appear on the knees, face, fingers, and around the nails.
- Flat warts are small, smooth warts appearing in clusters on the back of the hands, face, or legs.
- Plantar warts are those appearing on the soles of the feet. They can be painful because of their weight-bearing location on the feet.
- Filiform warts form long, thin projections around the eyes, face, and neck.
- Genital warts are small, cauliflower-shaped, or flat lesions. They occur on the genital areas including the vagina, cervix, vulva, penis, scrotum, and anus. They are usually painless but they can bleed, itch, or have some discharge.
- Precancerous lesions or cervical dysplasia are abnormal cells in the cervix. These are painless and can only be detected with a Pap smear.