Genital human papillomavirus (HPV) is the most common sexually transmitted infection (STI). The virus infects the skin and mucous membranes. There are more than 40 HPV types that can infect the genital areas of men and women, including the skin of the penis, vulva (area outside the vagina), and anus, and the linings of the vagina, cervix, and rectum. You cannot see HPV. Most people who become infected with HPV do not even know they have it.
Most people with HPV do not develop symptoms or health problems. But sometimes, certain types of HPV can cause genital warts in men and women. Other HPV types can cause cervical cancer and other less common cancers, such as cancers of the vulva, vagina, anus, and penis. The types of HPV that can cause genital warts are not the same as the types that can cause cancer.
HPV types are often referred to as "low-risk" (wart-causing) or "high-risk" (cancer-causing), based on whether they put a person at risk for cancer. In 90% of cases, the body's immune system clears the HPV infection naturally within two years. This is true of both high-risk and low-risk types.
Genital warts usually appear as small bumps or groups of bumps, usually in the genital area. They can be raised or flat, single or multiple, small or large, and sometimes cauliflower shaped. They can appear on the vulva, in or around the vagina or anus, on the cervix, and on the penis, scrotum, groin, or thigh. Warts may appear within weeks or months after sexual contact with an infected person. Or, they may not appear at all. If left untreated, genital warts may go away, remain unchanged, or increase in size or number. They will not turn into cancer.
Cervical cancer does not have symptoms until it is quite advanced. For this reason, it is important for women to get screened regularly for cervical cancer.
Other less common HPV-related cancers, such as cancers of the vulva, vagina, anus and penis, also may not have signs or symptoms until they are advanced.
Genital HPV is passed on through genital contact, most often during vaginal and anal sex. A person can have HPV even if years have passed since he or she had sex. Most infected persons do not realize they are infected or that they are passing the virus to a sex partner.
Very rarely, a pregnant woman with genital HPV can pass HPV to her baby during vaginal delivery. In these cases, the child may develop warts in the throat or voice box -- a condition called recurrent respiratory papillomatosis (RRP).
HPV can cause normal cells on infected skin or mucous membranes to turn abnormal. Most of the time, you cannot see or feel these cell changes. In most cases, the body fights off HPV naturally and the infected cells then go back to normal.
Sometimes, low-risk types of HPV can cause visible changes that take the form of genital warts.
If a high-risk HPV infection is not cleared by the immune system, it can linger for many years and turn abnormal cells into cancer over time. About 10% of women with high-risk HPV on their cervix will develop long-lasting HPV infections that put them at risk for cervical cancer. Similarly, when high-risk HPV lingers and infects the cells of the penis, anus, vulva, or vagina, it can cause cancer in those areas. But these cancers are much less common than cervical cancer.
HPV infection. Approximately 20 million Americans are currently infected with HPV, and another 6.2 million people become newly infected each year. At least 50% of sexually active men and women acquire genital HPV infection at some point in their lives.
Genital warts. About 1% of sexually active adults in the U.S. have genital warts at any one time.
Cervical cancer. The American Cancer Society estimates that in 2008, 11,070 women will be diagnosed with cervical cancer in the U.S.
Other HPV-related cancers are much less common than cervical cancer. The American Cancer Society estimates that in 2008, there will be:
3,460 women diagnosed with vulvar cancer;
2,210 women diagnosed with vaginal and other female genital cancers;
1,250 men diagnosed with penile and other male genital cancers; and
3,050 women and 2,020 men diagnosed with anal cancer.
Certain populations may be at higher risk for HPV-related cancers, such as gay and bisexual men, and individuals with weak immune systems (including those who have HIV/AIDS).
RRP is very rare. It is estimated that less than 2,000 children get RRP every year.
A vaccine can now protect females from the four types of HPV that cause most cervical cancers and genital warts. The vaccine is recommended for 11 and 12 year-old girls. It is also recommended for girls and women age 13 through 26 who have not yet been vaccinated or completed the vaccine series.