Merck Manual

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Human Papillomavirus (HPV) Infection

(Genital Warts; Condylomata Acuminata; Venereal Warts)


Sheldon R. Morris

, MD, MPH, University of California San Diego

Last full review/revision Apr 2020| Content last modified Apr 2020
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Human papillomavirus (HPV) causes warts. Some types of HPV cause skin warts, and other types cause genital warts (growths in or around the vagina, penis, or rectum). Infection with some HPV types can lead to cancer. HPV is sexually transmitted.

  • Different types of human papillomavirus (HPV) cause different infections, including visible genital warts and less visible genital warts in the cervix, vagina, vulva, urethra, penis, anus, as well as common skin warts.

  • Genital warts grow rapidly and sometimes cause burning pain.

  • Some types of HPV infection increase the risk of cancers of the cervix, vagina, vulva, penis, anus, and throat.

  • Doctors identify visible warts based on their appearance, and they examine the cervix and anus to check for less visible warts.

  • Vaccines can prevent most types of HPV infection that can cause cancer.

  • Visible warts can usually be removed with a laser or by freezing (cryotherapy) or surgery, but sometimes drugs are applied to the warts.

HPV is the most common sexually transmitted disease (STD). HPV is so common that nearly all sexually active men and women get the virus at some point in their life. In the United States, about 14 million people become newly infected with HPV each year. Before the HPV vaccine became available, each year roughly 340,000 to 360,000 patients sought care for genital warts caused by HPV. As more and more people are being vaccinated against HPV, the percentage of people with evidence of HPV infection has been decreasing.

Most infections go away within 1 to 2 years, but some persist. Persistent infection caused by some types of HPV can increase the risk of certain types of cancer.

There are over 100 known types of HPV. Some types cause common skin warts. Other types cause different types of genital infections:

  • External (easily seen) genital warts: These warts are caused by certain types of HPV, especially types 6 and 11. Types 6 and 11 are unlikely to cause cancer. These types are transmitted sexually and infect the genital and rectal areas.

  • Internal (less visible) genital warts: Other HPV types, especially types 16 and 18, infect the genital area but do not cause easily visible warts. They cause tiny flat warts on the cervix or in the anus, which may be visible only with a magnifying instrument called a colposcope. Warts may also develop in the vagina, vulva, urethra, penis, anus, or throat. These less visible warts usually cause no symptoms, but the HPV types that cause them increase the risk of developing cervical cancer and vaginal, vulvar, penile, anal, and throat cancer. Therefore, these warts should be treated. Being infected with the human immunodeficiency virus (HIV) increases the risk of developing HPV-related cancer.

The types of HPV that affect the genital and rectal areas are usually spread during vaginal or anal intercourse but may also be spread through other types of contact.

HPV can also be spread during oral sex, causing infections of the mouth and increasing the risk of throat cancer.

Did You Know...

  • Some types of HPV that causes genital warts can also cause cancer.


In men, warts usually occur on the penis, especially under the foreskin in uncircumcised men, or in the urethra. In women, genital warts occur on the vulva, vaginal wall, cervix, and skin around the vaginal area. Genital warts may develop in the area around and inside the anus, especially in people who engage in anal sex.

Warts cause no symptoms in many people but cause occasional burning pain, itching, or discomfort in some.

The warts usually appear 1 to 6 months after infection with HPV, beginning as tiny, soft, moist, pink or gray growths. They grow rapidly and become rough, irregular bumps, which sometimes grow out from the skin on narrow stalks. Their rough surfaces make them look like a small cauliflower. Warts often grow in clusters.

Warts may grow more rapidly and spread more widely in pregnant women and in people who have a weakened immune system, such as those who have HIV infection.


  • For external genital warts, a doctor's evaluation

  • For internal genital warts, colposcopy or anoscopy

External genital warts usually can be diagnosed based on their appearance. If warts look unusual, bleed, become open sores (ulcerate), or persist after treatment, they should be removed surgically and examined under a microscope to check for cancer. Because syphilis can cause certain types of genital warts, doctors usually do a blood test for syphilis.

Colposcopy (use of a binocular magnifying lens to examine the cervix) is done to check for less visible, internal warts on the cervix. Anoscopy (use of a viewing tube to examine the interior of the anus) is done to check for warts in the anus. A stain may be applied to the area so that warts can be seen more easily.

A sample taken from a wart may be analyzed using tests, such as the polymerase chain reaction (PCR). This test produces many copies of a gene, which may enable doctors to identify HPV’s unique genetic material (DNA). These tests help confirm the diagnosis and enable doctors to identify the type of HPV.

Testing people who have no symptoms (screening) is usually not recommended. Women age 30 to 65 are an exception. These women should be screened when they have a Papanicolaou (Pap) test. If HPV is detected, colposcopy is done. Often, a sample of tissue is removed for examination under a microscope (biopsy).


There are three vaccines to choose from to vaccinate against HPV:

  • Nine-valent: Protects against nine types of HPV

  • Quadrivalent: Protects against four types of HPV

  • Bivalent: Protects against two types of HPV

Only the nine-valent vaccine is now available in the United States.

All three HPV vaccines protect against the two types of HPV (types 16 and 18) that cause about 70% of cervical cancers. The quadrivalent vaccine includes protection against the two types of HPV (types 6 and 11) that cause more than 90% of genital warts and the nine-valent vaccine adds protection against 5 other types of HPV (types 31, 33, 45, 52 and 58) that cause about 15% of cervical cancers.

The nine-valent vaccine and quadrivalent vaccine are recommended for everyone age 9 to 26 years who was not previously vaccinated. Adults age 27 to 45 years may benefit from the nine-valent vaccine and should discuss with their doctor whether to be vaccinated. The bivalent vaccine is recommended only for girls and women, not for boys and men.

These vaccines are given by injection into a muscle, usually in the upper arm. Preferably, the vaccine is given at age 11 or 12 years, but it can be started as early as 9 years. Children younger than 15 years receive two doses; people 15 years and older receive three doses.

Consistent correct use of male condoms can reduce the risk of HPV infection and disorders related to HPV, such as genital warts and cervical cancer. Condoms may not completely eliminate the risk because HPV can infect areas that are not covered by the condom.

Other general measures can also help prevent HPV infection (and other sexually transmitted diseases):

  • Avoidance of unsafe sex practices, such as frequently changing sex partners or having sexual intercourse with prostitutes or with partners who have other sex partners

  • Prompt diagnosis and treatment of the infection (to prevent spread to other people)

  • Identification of the sexual contacts of infected people, followed by counseling or treatment of these contacts

Not having sex (anal, vaginal, or oral) is the most reliable way to prevent sexually transmitted diseases but is often unrealistic.


  • Usually laser, electrocautery, freezing, or surgery

  • Sometimes various topical treatments

If the immune system is healthy, it often eventually controls HPV and eliminates the warts and the virus, even without treatment. HPV infection is gone after 8 months in half of people and lasts longer than 2 years in fewer than 10%. If people with genital warts have a weakened immune system, treatment is required, and the warts often return.

No treatment for external warts is completely satisfactory, and some treatments are uncomfortable and leave scars. External genital warts may be removed with a laser or an electric current (electrocautery) or by freezing (cryotherapy) or surgery. A local or general anesthetic is used, depending on the number and size of the warts to be removed.

Alternatively, podophyllin toxin, imiquimod, trichloroacetic acid, or sinecatechins (an ointment made from extracts of green tea) can be applied directly to the warts. However, this approach requires many applications over weeks to months, may burn the surrounding skin, and is frequently ineffective. After treatment, the area may be painful. Imiquimod cream causes less burning but may be less effective. The warts may return after apparently successful treatment.

For warts in the urethra, a viewing tube (endoscope) with surgical attachments may be the most effective way to remove them, but this procedure requires a general anesthetic. Drugs, such as thiotepa inserted into the urethra or the chemotherapy drug 5-fluorouracil injected into the wart, are often effective.

Interferon-alpha injections into the wart have been found to be somewhat effective.

In men, circumcision reduces the risk of getting HPV infection, as well as HIV infection and genital herpes, but not syphilis.

All sex partners should be examined for warts and other STDs and treated, if necessary. Sex partners should also have regular examinations to check for HPV infection.

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