Nearly three-fourths of adults in the United States have been infected with human papillomavirus (HPV) at some time in their lives, although the majority is unaware of it. Different types of HPV produce warts in different areas, such as hands or feet, but the focus of most recent attention has been the sexually transmitted types. Most people with HPV infection have no symptoms, but many experience warts in the genital or anal area, and women may have an abnormal Pap smear as a result. As in other areas of the body, these warts will often go away on their own. A few of the many types of this virus may persist, however, and even cause cervical cancer, the second most common cancer in women worldwide. Most importantly, infection with this virus -- and its associated cancer -- is now preventable with the use of a recently approved vaccine.

Transmission: How Does Someone Get HPV?

Anyone who is sexually active can get HPV, as it spreads readily by direct genital contact. HPV can be present in the skin and transmitted even in the absence of visible genital warts, but transmission is probably more likely to occur when warts are present. More than 30 types of HPV can infect the genital tract. About 90 percent of genital warts are caused by types 6 and 11, while types 16 and 18 cause more than 70 percent of cervical cancers and precancerous changes.

The types of HPV causing warts in non-genital areas are different, so you do not get genital warts from touching warts on hands or feet. It is also extremely unlikely that a person could acquire genital HPV from a toilet seat, bathtub, towel, or other inanimate object. The time to appear-ance of warts after exposure is quite variable: some develop within a few weeks after sexual contact, in others there may be years before warts appear. In some relationships, despite long-term contact, warts never appear. This makes it nearly impossible to know exactly when or from whom someone got the virus. Furthermore, approxi-mately 75-90 percent of HPV infections clear on their own within a year of initial infection.

Signs and Symptoms

Genital warts usually arise as small bumps or growths, slightly pink or skin-colored, sometimes roughened, similar to warts in other areas, and may be located anywhere around the genital or anal areas. They can itch, burn at times, or rarely, bleed. Most often they cause no symptoms at all, but are simply noted as a new finding on the skin. When present inside the vagina or on the cervix, warts are usually found only at the time of pelvic examination.

The most dreaded outcome of HPV infection is cancer. This occurs most often in the cervix (in women), less frequently in anal or other genital areas (in men or women). There are usually no symptoms of this cancer, which can be detected by routine Pap smear screening in women, or biopsy of a suspicious area in men or women with warts.

Diagnosis and Testing

Warts can be difficult to see, often occurring in skin folds, and may be so small as to require magnification for identification. A biopsy to remove a small piece of the wart may give a definitive answer, but is not usually needed if the appearance is typical. If warts are suspected but not seen, or to help identify a particular bump as a wart, a small amount of acetic acid (vinegar) may be applied. This painless test aids in diagnosis by turning the area white if truly a wart.

For the "flat warts" with less typical appearance often found internally in vaginal or anal areas, the use of a magnifying lens called a colposcope together with acetic acid can be especially informative. Because abnormalities on Pap smears in women are often the first sign of HPV infection, colposcopy with acetic acid helps to show the areas on the cervix most affected by HPV. In the past few years, an additional test has been added to Pap smears to detect the HPV types most likely to cause cervical cancer.

Treatment

Although there is no cure for HPV, there are several treatments available for warts to help with irritating symptoms, and perhaps prevent spread to partners. Most often this involves applying one of several topical medications to destroy the wart; these can cause temporary irritation or soreness. Other forms of wart treatment include cryotherapy (freezing, usually with liquid nitrogen), electrocautery (burning the wart tissue), laser, and even ultrasound.

Warts can also be directly removed with minor surgery, a method usually reserved for large warty areas, warts not responding to previous medical treatments, or warts in sensitive areas around the vagina, urethra, or anus. For abnormal Pap smear results that suggest early cancer or precancerous changes,specific treatment may be needed, including local surgery to remove the abnormal areas. Despite treatment with any of these methods, there remains a chance the warts can recur. An important warning: over-the-counter wart treatments for hand or foot warts are very irritating and should not be used in the genital area.

Prevention: Protecting Yourself and Others

Because of the prevalence of HPV in the United States, preventing the spread of this highly contact-contagious condition is no easy matter. The Centers for Disease Control and Prevention (CDC) has estimated that 75-80 percent of sexually active adults acquire a genital HPV infection before the age of 50. Short of abstinence, the surest way for an uninfected person to remain so is to maintain a monogamous relationship with an uninfected partner. While unprotected sexual contact with multiple partners certainly increases the risk, HPV is so prevalent that on average an individual acquires it more through bad luck than as a result of promiscuity.

Condoms are helpful, but many genital warts occur in areas not covered by a condom. If someone has visible genital warts, it is safest for that person to refrain from sexual activity until the warts are treated. Fortunately, it is extremely unusual for HPV or genital warts to pose any significant problem for the health of a mother or baby during pregnancy. A baby that is exposed to HPV during vaginal delivery, however, may rarely develop warts in the throat or voice box.

Over the past 50 years, screening with Pap smears has reduced the death rate from cervical cancer in the United States by 70 percent. Unfortunately, many women miss out on the screening or do not seek it out, and screening programs are less well established in other countries. No test is perfect, however, and cervical cancer still occurs. With the availability of a new vaccine, it now becomes preventable.

HPV Vaccine: Immunization Against Cancer

In one of the most significant preventive healthcare achievements of the last decade, a vaccine (Gardasil) has been developed to prevent cervical cancer due to HPV. After years of clinical study, the vaccine was approved by the U.S. Food and Drug Administration (FDA) in June, 2006 for use in girls and women aged 9 to 26 to prevent diseases caused by HPV types 6, 11, 16, and 18. Gardasil is given in 3 separate injections: at the first visit, then 2 and 6 months later. The cost of the 3-dose course, around $360, is expected to be covered by most insurers. Another vaccine (Cervarix) will probably become available soon, targeting HPV types 16 and 18 only.

HPV vaccine is now recommended routinely for girls 11 and 12 years old and on a "catch-up" basis for girls 13 to 18 years old. It is licensed to be given safely to girls as young as 9. However, for women 19 to 26 years old, or older, data are inadequate at this time to support universal HPV vaccination. The vaccine is expected to be less beneficial in older women with more lifetime sexual partners and greater chance of prior exposure to HPV. It has not yet been studied sufficiently to be administered to men, but studies in progress suggest a protective immune response to the vaccine.

The vaccine was found to be quite safe in clinical studies, and almost 100 percent effective at preventing persistent infection or precancerous changes associated with HPV types 6, 11, 16, and 18. It is estimated that vaccination of all 11- and 12-year-old girls in the United States would prevent more than 200,000 HPV infections, 100,000 abnormal Pap smears, and 3,300 cases of cervical cancer. This safe, effective intervention promises to make a major impact on the second most common cancer in women, and may pave the way for additional vaccines against cancer in the future.

For more information:

American Social Health Association, 800-230-6039, www.ashastd.org

National HPV and Cervical Cancer Public Education Campaign, 866-280-6605, www.cervicalcancercampaign.org

American Cancer Society, www.cancer.org

Centers for Disease Control and Prevention, www.cdc.gov/std/HPV/STDFact-HPV.htm