Chances are you have been exposed to the human papillomavirus (HPV) and don't even know it. In fact, most adults who have been sexually active have been exposed to HPV, with as many as 20 million Americans estimated to be infected with the genital form of the virus.
It is estimated that as many as 75 percent of the reproductive-age population has been infected with one or more types of genital HPV and up to 5.5 million new infections occur each year.
The good news: In the vast majority of cases, the virus causes no symptoms or health problems. The bad news: It causes nearly all cases of cervical cancer, which the American Cancer Society estimates will affect an estimated 10,370 women in 2005, killing about 3,710.
In many ways, the issues raised by HPV infection are similar to those raised by genital herpes. Both are incurable and rarely have symptoms. Both can cause medical problems in some women and both have become widespread in this country.
Unlike herpes, however, HPV causes cancer in a small percentage of women and men. In addition to cervical cancer, HPV can also cause cancers of the vulva, penis, head, neck and anus, but these diagnoses are extremely rare.
The viruses are called papillomavirus because they tend to cause warts, or papillomas—benign (noncancerous) tumors. Warts may appear on the hands and feet, or on the genital area. The strains of HPV that cause warts to grow on hands and feet, however, are rarely the same type that causes warts in the genital area. And, not all HPV viruses cause warts.
There are about 200 different types of HPV. Only about 40 strains are spread through sexual contact and only a handful are associated with cervical cancer. More than 95 percent of HPV viruses cause no symptoms and problems.
The U.S. Food and Drug Administration recently approved a HPV vaccine—called Gardasil—for women ages 13 to 26 after clinical trials showed the vaccine is safe and 100 percent effective in preventing HPV strains 16 and 18, which cause 70 percent of cervical cancers. Gardasil, given in three injections over six months, is also 99 percent effective in preventing HPV strains 6 and 11, which cause about 90 percent of genital wart cases. Although Gardasil prevents the bulk of HPV strains, it doesn't protect against all of them, so the FDA recommends it as a complement to Pap tests. Furthermore, the vaccine does not work if a woman is already infected with one of these HPV types. It has to be given before infection.
The number of invasive cervical cancer cases and deaths in the U.S. has steadily decreased over the past several decades because of prevention and early detection by screening—so, despite the breakthrough of an HPV vaccine, Pap tests remain a recommended screening option for abnormalities that may develop into cervical cancer.
HPV is spread by skin-to-skin contact with an HPV-infected area. Infections can be subclinical, meaning the virus lives in the skin without causing symptoms. This is why many people with HPV do not know they have it or that they could spread it. It can take weeks, months or years for genital warts to surface after sexual relations with an infected person.
Researchers already know that condoms don't always protect against the virus because warts can grow on areas of the genitals not covered by a latex barrier. A study in Great Britain, for example, found evidence that HPV may be transmitted from one's hands to a partner's genitals. Consequently, some lawmakers are pushing for better labeling of condoms so the public knows that no barrier contraceptive method can completely safeguard against the virus.
Researchers don't know whether people infected with genital HPV but who don't have symptoms are as contagious as people with symptoms. They also don't know how much HPV is transmitted through sexual contact versus skin-to-skin contact.