Human papillomavirus (HPV) is a common infection that affects the skin and mucous membranes of both men and women. The term HPV refers to a group of viruses. They are called papillomaviruses because certain types may cause warts, or papillomas. Not all types of HPV cause warts, but all warts are caused by HPV. According to the Centers for Disease Control and Prevention (CDC), about 100 types of HPV have been identified, more than 30 of which are passed through sexual activity. The type of HPV that infects the genitals is called genital HPV and is a sexually transmitted disease (STD). The CDC estimates that at least 50 percent of sexually active women and men will develop HPV at some time in their lives.

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. Infection by more than one different type of HPV seems to increase this risk. 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).

HPV is one of 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.

Certain types of HPV may also cause cervical dysplasia (precancerous changes in the cervix) in women. Almost all cases of precancerous changes in the cervix are caused by HPV. An estimated 9,700 cases of invasive cervical cancer will be diagnosed in the United States in 2006, according to the American Cancer Society and about 3,700 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. Rates of cervical cancer are much higher outside the United States, which can be attributed to less rigorous gynecological screening for abnormal cervical changes.

The cancerous effects of HPV in men are much more rare. Penile cancer (one of the cancers linked to HPV) accounts for 0.2 percent of all cancers in men. Anal cancer is also very rare, and is more common among gay and bisexual men.

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 1 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.

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.  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.