Human papillomaviruses (HPV)

HPV infections usually go unnoticed, don't cause any symptoms, and clear up on their own. In rare cases, though, they can cause cervical cancer. The cancer may develop years or even decades after the woman was infected.

More than 200 different types of HPV are currently known. Some cause warts on the skin (also called papillomas) – for instance on the face, hands or feet. About 40 HPV strains infect the skin and mucous membranes in the genital area and are spread through sexual contact. People can have several different types of HPV at the same time.

Some types of HPV are harmless. They can cause unpleasant warts known as condylomas in the genital area, but these warts aren’t dangerous. On average, about 1% of the population have these genital warts, but they are more common in sexually active young people. In about a third of the people who have them, the warts go away on their own. The most common harmless types are HPV 6 and HPV 11.

High-risk HPV types often enter the cells of the mucous membrane around the opening of the cervix, where the vagina and cervix meet. There they may lead to abnormal cell changes (dysplasia). The medical term for this is cervical intraepithelial neoplasia (CIN). These abnormal cells can develop into cancer over the years. But that rarely happens. Twelve types of HPV are known to increase the risk of cervical cancer (cervical carcinoma). The main ones are HPV 16 and 18. These are also the types of HPV that are most often found in tumor tissue.

In addition to cervical cancer, HPV viruses can also increase the risk of dysplasia affecting the external female sex organs such as the vulva (VIN) and the vagina (VAIN), as well as the anus (AIN) and the mouth and throat area. In men, dysplasia of the penis (PIN) is possible. Compared to cervical dysplasia, dysplasia on these parts of the body is less likely to develop into cancer.

HPV is very common, so most men and women who are sexually active will be infected at least once in their lives. The body’s immune system usually fights off the viruses successfully, and they disappear without having caused any symptoms. People can get infected with HPV more than once.

Because HPV viruses can infect the entire genital area, you can catch HPV through any intimate contact in that area (not only sexual intercourse). Infection through body fluids like sperm, blood or saliva is considered to be unlikely. But viruses might be spread during oral sex if mucous membranes in the mouth touch areas of skin infected with HPV.

HPV infection is equally common in men and women. The possible consequences of the infection, such as cancer, are less common in men, though. The risk of infection in women is highest up until the age of about 30.

HPV infections can be diagnosed directly with an HPV test – or indirectly with a Pap test (smear test), which detects abnormal cells in the mucous membranes.

Because HPV is so common, you can already become infected with HPV the first time you have sexual contact with someone. If you would like to protect yourself from infection, you would either have to avoid sexual contact altogether or be sure that your partner has also never had sexual contact with other people.

Condoms don’t cover all areas of skin in the genital area that could be infected, so they don’t offer full protection from HPV. But they still reduce the risk of infection. And they provide protection against many other sexually transmitted diseases too.

Girls and boys can have a vaccine to protect them from infection with certain types of HPV. This also reduces the risk of cervical cancer.

HPV infections only rarely cause symptoms, in men or in women. Because women are examined more frequently than men, they are also more likely to be tested for HPV – for example, as part of a screening program. Some women find it difficult to tell their partner about their infection. But both partners may be infected, even in long-term relationships. It is usually not possible to find out who became infected first or how long ago they were infected. And that doesn’t affect the course of this usually harmless infection either.

It is not known whether partners can infect each other again and again. But research suggests that abnormal cells on the woman’s cervix are more likely to go back to normal again if a couple regularly uses condoms when having sex. This supports the belief that condoms offer at least some protection.

Most HPV infections clear up on their own because the immune system recognizes the viruses and kills them. If that doesn't happen and the HPV infection lasts for a long period of time, the tissue may change. This tissue often becomes normal again on its own. But it may stay abnormal or change even more. Sometimes, depending on the type of virus, the cells and tissue change so much that they develop into cancer.

So far there's no treatment to fight the HPV viruses themselves.

Many genital warts can’t be seen or felt, but some form hard nodules with an uneven surface. Their size ranges from just a few millimeters to several centimeters, and they may be a reddish, brownish, or whitish color. They usually appear in clusters. Depending on their size and location, they can cause symptoms like itching or burning.

Genital warts can be treated locally with a medication (a cream or a solution), or they can be removed surgically. The treatment options will depend on the texture and location of the warts, and how far they have spread.