Human papillomavirus (HPV) is the most common sexually transmitted infection. There are more than 40 types of HPV that can infect the genital areas of men and women. You cannot see HPV. Most people who become infected with HPV do not know they have it.

What are the symptoms of HPV?
Most people with HPV do not develop symptoms or health problems. But sometimes, certain types of HPV can cause genital warts. Other 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 different from those that can cause cancer.

HPV types are often referred to as “low-risk” (wart-causing) or “high-risk” (cancer-causing).  The body’s immune system clears up the HPV infection within two years in 90% of cases, for 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. 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.

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, may not have signs or symptoms until they are advanced.

How do people get HPV?
Genital HPV is passed on through genital contact. Most infected people do not realize they are infected or that they are passing the virus to a partner.

How does HPV cause cancer?
HPV can cause normal cells on infected skin or mucous membranes to turn abnormal. Most of the time, you cannot see or feel these changes, and in most cases, the body fights off  the infection and returns the infected cells  to normal. 

• Sometimes, low-risk types of HPV cause visible changes that take the form of genital warts.
• If a high-risk HPV infection is not cleared up by the immune system, it can linger for many years and turn abnormal cells into cancer. 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, it can cause cancer in those areas. But these cancers are much less common than cervical cancer.

How common is HPV and related diseases?
Approximately 20 million Americans are currently infected with HPV, and another 6.2 million people become infected each year. At least 50% of sexually active men and women will contract a genital HPV infection.

How can HPV be prevented?
The HPV vaccine can protect women from the four types of HPV that cause most cervical cancers and genital warts. This vaccine is recommended for 11- and 12-year-old girls, as well as girls and women aged 13 through 26 who have not completed the vaccine series.
 
For those who choose to be sexually active, condoms may lower the risk of HPV and HPV-related diseases, such as genital warts and cervical cancer — if used  correctly and consistently.  But HPV can infect areas that are not covered by a condom — so condoms may not fully protect against HPV. You may lower your chances of getting HPV by choosing a mutually exclusive relationship, but the only sure way to prevent HPV is to avoid sexual activity.

Source: www.cdc.gov