There are more than 100 types of the human papilloma virus, or HPV. About 40 of these viruses are responsible for genital warts in both men and women, according to the Centers for Disease Control. HPV infection is the most common sexually transmitted infection, with about 20 million people in the United States currently infected. Genital warts are the most common result of an HPV infection. But some types of HPV also carry a high risk of cancer: cervical, vulvar, vaginal or anal cancer for women and penile or anal cancer for men, according to MedlinePlus.
Transmission of HPV
HPV is the most common sexually transmitted infection. The virus is transmitted from person to person by genital contact, usually during vaginal or anal sex. Other skin-to-skin contact in the genital region may also transfer the virus from an infected person to an uninfected person, according to the Mayo Clinic. The National Institute of Allergy and Infectious Diseases reports that an infected person will transfer the virus to an uninfected sexual partner about two thirds of the time and that symptoms usually appear in the partner within three months.
Genital Warts
Some people infected with HPV never develop symptoms, although asymptomatic people are still able to transmit the virus to uninfected partners. According to the Centers for Disease Control, 90 percent of infected people without symptoms are virus-free within two years because the immune system destroys the virus. But in symptomatic people, the most common finding is the appearance of one or more genital warts. These nonmalignant growths may be large or small and they may develop singly or in groups.
HPV and Cervical Cancer
There is a close relationship between HPV infection and cervical cancer. The American Cancer Society reports that almost 99 percent of cervical cancers are caused by HPV. It also says that many of the 500,000 cases of precancerous cell changes in the cervix, vagina and vulva detected in American women each year are due to HPV. Sometimes, these precancerous changes appear many years after a women is infected with HPV. Precancerous cells in the cervix return to normal in some women while in others they develop into cancer. The most common symptoms of cervical cancer are unusually heavy menstrual bleeding or bleeding between menstrual periods.
Risk Factors
Several factors raise the likelihood that a person will contract HPV. First, the risk is related to the number of sex partners a person has, with higher numbers increasing the risk. Sex with a person who has had multiple partners also increases the risk of transmission. Genital infection is most often diagnosed in sexually active girls and women under 25 years old, possibly because younger people are more susceptible to the virus. Anyone whose immune system is compromised, for example through immunosuppressive drugs or because of HIV infection, is also at a higher risk of contracting an HPV infection.
Prevention of HPV
One way a person may avoid contracting HPV is to limit the number of sexual partners. Use of a condom may help, although the Centers for Disease Control says this is not a guarantee, because the virus may also be transmitted through skin to skin contact in the genital area. There are two vaccines that can prevent infection with the most common forms of HPV. These are called Cervarix and Gardisil. Both vaccines prevent cervical cancer, and Gardisil also prevents genital warts. The vaccines may be given to girls as young as 9 years old and they are also recommended for older girls and young women who have not previously received any vaccine. For boys, Gardisil is recommended to prevent HPV infection and genital warts. Three doses are given, and the Centers for Disease Control recommends that all three doses should be of the same vaccine brand.
