Human papillomavirus (HPV) is a common infection that affects skin and mucous membranes. The term HPV refers to a group of viruses. They are called papillomaviruses because certain types may cause warts, or papillomas.

The term HPV actually refers to a group of viruses. According to the Centers for Disease Control and Prevention (CDC), about 100 types of HPV have been identified, over 30 of which are passed through sexual activity. The type of HPV that infects the genitals is called genital HPV, which is a sexually transmitted disease (STD). The CDC estimates that at least 50 percent of all sexually active people will develop HPV at some time in their lives.

HPV is not genital herpes, another STD. Both are caused by a virus, but HPV can cause genital warts (known as condylomata acuminatum) and herpes can cause blisters or sores. Certain types of HPV may also cause cervical dysplasia (precancerous changes in the cervix). In both cases, the patient may experience no symptoms. There is no cure for either disease, but in most cases of HPV, the body’s immune system fights off the infection, and is able to eradicate the virus from the system. With herpes, the virus lays dormant in the body and can recur.

HPV is the most common sexually transmitted disease in the United States. According to the CDC, approximately 20 million people are infected with HPV. About 6.2 million Americans get a new genital HPV infection each year, but the vast majority of people are unaware of it. The virus typically causes no symptoms or health problems in the majority of cases, according to the National Women’s Health Resource Center.

Some HPV types cause warts in areas such as hands and feet. A few types cause genital warts (single or multiple growths or bumps that appear in the genital area and can be cauliflower shaped). Certain types of genital HPV, known as high-risk HPV, are a major risk factor for cervical cancer. Several studies have suggested that HPV infection plays a role in cancers of the anus, vulva, vagina and penis, as well as some cancers of the oropharynx (the middle part of the throat that includes the soft palate, bases of the tongue and tonsils).

Almost all cases of precancerous changes in the cervix are caused by HPV. An estimated 10,000 cases of invasive cervical cancer will be diagnosed in the United States in 2006, according to the American Cancer Society and nearly 4,000 women will die from the disease. Although most people are exposed to the cell-changing types of HPV at some point in their lives, not everyone will develop abnormal cell changes.

Most women who have had genital warts in the past (but no longer have them) will not experience problems during pregnancy or childbirth. If genital warts develop during pregnancy, they may grow and/or bleed. Genital warts that grow larger during pregnancy can make it difficult for a woman to urinate. Genital warts during pregnancy may require removal by a physician. In addition, warts may very rarely block the birth canal, requiring the physician to perform a Caesarean section to deliver the baby.

In rare instances, a pregnant woman may pass HPV to her baby. As a result, warts may develop in the baby’s throat (laryngeal papillomatosis). This is a potentially life-threatening condition that requires repeated laser surgery to prevent blockage of the breathing passages. Fortunately, this is extremely rare, occurring in only one per 30,000 cases of HPV infected mothers.  

It is unknown when a person with HPV can transmit the virus, how long a person with HPV is able to transmit it and why some people exposed to HPV gets warts while others do not.