From Planned Parenthood -

HPV — The Most Common Sexually Transmitted Virus

In their efforts to discredit the effectiveness of condoms, right-wing ideologues who want to institute sexual abstinence until marriage as a standard for all Americans have instigated an alarmist and misleading public policy and media campaign about very common, and usually benign, sexually transmitted infections - the human papilloma viruses (HPVs). State and federal legislative bills have been introduced, misinformation has been disseminated, and lawsuits have been threatened to inspire public doubt about condom use and unnecessary alarm among the many sexually active women and men - as many as three out of four - who have been infected with this extremely common, and most often harmless, infection (Cal. SB 977, 2001; Cates, 1999; "House Approves…", 2000; Leishman, 2001; Schneider & Cirmo, 2000).

While a handful of sexually transmitted HPVs can cause a variety of conditions that can lead to dangerous cancers if they remain untreated, it is a gross and dangerous exaggeration to typify HPV as a "dreaded virus" and safer-sex, public health messages advocating condom use as a "conspiracy" ("House Approves…", 2000). This fact sheet will give sexually active women and men the facts they need to understand the real nature of HPVs, what conditions HPVs cause, how those conditions can be effectively managed, and how one may reduce one's own risk of becoming infected.

Human Papilloma Virus (HPV) is a common infection that affects skin and mucous membranes, and is the cause of warts. Some types cause warts in the genital area - others cause common skin warts in other areas such as the hands or feet. Approximately 100 viral types of HPV have been identified, and about one third of these are associated with sexually transmitted genital infections (Koutsky & Kiviat, 1999). HPV has affected humans for thousands of years - ancient Greek and Roman medical records described genital lesions consistent with genital warts and associated them with sexual activity (Jay & Moscicki, 2000).

Today HPV is the most common sexually transmitted infection in the U.S. - yet 70 percent of Americans have never heard of it (Jay, 2000; KFF, 2000). Up to 20 million Americans are currently infected with sexually transmitted HPV, and it is estimated that 75 percent of reproductive age women and men have been infected with genital HPV at some point in their lives (Cates, 1999). The highest rates of genital HPV infection are found in adults between the ages of 18 and 28 (Koutsky, 1997). HPV is also prevalent among people with immunosuppressive disorders, such as HIV (Koutsky & Kiviat, 1999). HPV is believed to be widespread across racial groups and to have very little variation in prevalence across regions in the U.S. (CDC, 2000).


HPV is transmitted by direct skin-to-skin contact with an infected individual. Transmission is usually from vaginal, oral, or anal sexual contact, and can occur whether or not warts or other symptoms are present (McDermott-Webster, 1999). The virus can also be transmitted from mother to infant during childbirth (Puranen, 1997). Very rarely, this "vertical" transmission is associated with development of recurrent laryngeal papillomatosis (warts on the throat) for the child - about 2,000 out of every 4 million newborns (Jay & Moscicki, 2000). This is a serious condition that may require frequent laser surgery to prevent obstruction of the infant's airways (NIAID, 2001). Some research also suggests that genital HPV can be transmitted through nonsexual routes, via fomites - inanimate objects such as towels or underwear - but more research must be conducted to examine these modes of transmission (Carson, 1997; Keller, et al., 1995; Stevens-Simon, et al., 2000).

Natural History

Although there is currently no "cure" for genital HPV infection, most cases are transient and clear themselves without medical intervention (CDC, 2001; Elfgren, et al., 2000; Ho, et al., 1998). One study designed to determine the natural history of genital HPV infection followed college women for three years (Ho, et al., 1998). HPV was detected using a sensitive DNA test that detects small amounts of HPV, even when there are no symptoms present. While there was a high rate of HPV infection (43 percent tested positive for HPV at some point over the study period), the average duration of HPV infection was eight months. Repeated HPV DNA testing showed that seventy percent of the women cleared their HPV infections within one year through the natural immune process, and only nine percent continued to be infected after two years. Another study conducted in Sweden supported these findings, with a five-year clearance rate of 92 percent (Elfgren, et al., 2000). In both studies, the viral type of HPV was a major determinant in the duration of infection, with types 16, AE7, 61, 18, and 73 having the longest average duration (Elfgren, et al., 2000; Ho, et al., 1998).

Subclinical HPV

HPV infection can be clinical (symptomatic) or subclinical (asymptomatic), and many people with HPV never know they have it (Verdon, 1997). HPV targets the deep, basal level of the skin and most often causes no clinical or microscopic changes in the cells of the skin (Keller, et al., 1995; Verdon, 1997). In some cases, subclinical HPV may cause cellular changes that are only detectable using clinical instruments or the study of cervical cells. These changes may be, in rare instances, the precursor to cancer cells (Lytwyn & Sellors, 1997).

HPV infections that cannot be seen with the naked eye may be seen with a variety of clinical tools:

* During a pelvic exam, a hand lens or colposcope may be used to magnify cervical and vaginal tissue (Verdon, 1997).

* Pap tests may reveal precancerous conditions of the cervix that are caused by HPV. Most often, early treatment can prevent cervical cancer (Keller, et al., 1995).

* In March 1999, the U.S. Food and Drug Administration approved the Hybrid Capture II HPV test to be used as a secondary test when Pap tests are inconclusive about whether or not there have been changes in the cells of the cervix. This test uses DNA-based technology to detect 13 high-risk types of HPV (those associated with an increased risk of cancer) ("HPV DNA Tests", 2000). The Hybrid Capture II has a sensitivity of about 90 percent, meaning that it is highly likely to detect HPV in the cervix if it is present (Cuzick, 2000). Consequently, in some cases, the Hybrid Capture II can help clinicians judge a woman's risk of HPV-related cervical disease. 

Genital Warts

Genital warts (condylomata acuminata) are the clinical, visible manifestation of genital HPV. In more than 90 percent of cases, they are caused by HPV types 6 and 11, which are considered low-risk types because they are not associated with increased risk of cancer (Jay & Moscicki, 2000). However, a person may be infected with more than one type of HPV at the same time.

It is estimated that one percent of the American population has genital warts, and women and men have similar rates, with a female to male ratio of 1.4:1 (Jay & Moscicki, 2000; Cockerell, 1995).

Genital warts usually start as small bumps that appear in the genital area or anus. They may be single or clusters and have a cauliflower-like appearance as they grow larger. In women, genital warts appear on the vulva, in the vagina, on the cervix, or in the anal area. In men, they appear on the foreskin, head or shaft of the penis, and in the anal area, urethra, and scrotum (Cockerell, 1995). Rarely, warts may also develop in the mouth or throat of a person who has had sexual contact with an infected person (Koutsky & Kiviat, 1999).

Genital warts usually are painless, but they may cause itching or irritation (Cockerell, 1995). Genital warts are very contagious, with an estimated rate of infection of between 30 and 60 percent from unprotected exposure (Jay & Mosicicki, 2000). The incubation period for genital warts is usually between three and six months, but it may last for years after exposure (ASHA, 1998; ASHA 2000).

Treating Genital Warts

Because there is no cure for HPV infections, the purpose of treatment is to control outbreaks of warts. Some clinicians choose not to treat warts immediately in certain individuals because it has been found that in 20-to-30 percent of people, genital warts clear spontaneously within three months (Verdon, 1997; Crabb, 1997).

Genital wart treatments fall into three categories:

* prescription topical chemicals designed to destroy wart tissue
* surgical methods to remove wart tissue
* approaches that target the underlying virus causing the wart

There are several chemicals that can be applied directly to genital warts. Some are prescribed for use at home, such as podofilox. Whenever these chemicals are used, the clinician's instructions must be followed precisely to reduce adverse side effects. Other chemical treatments include podophyllin, trichloroacetic acid (TCA), and bichloroacetic acid (BCA). Side effects of using chemicals to treat genital warts may include pain, redness, itching, burning, and swelling. Patients who are pregnant, have diabetes, are taking steroid drugs, or have poor circulation may be poor candidates for using some of these topical chemicals (Lewis, 1995).

There are several surgical methods to remove genital warts, including cryotherapy, in which individual warts are frozen off with liquid nitrogen. Another procedure is electrocautery, in which a high-frequency electric current from a wire is used to destroy the warts. Less commonly used surgical treatments include removal using scissors, scalpel, or lasers (Wright, 1998).

Least commonly used, interferon therapy is an expensive course of therapy that is designed to help the immune system target the underlying HPV infection. Interferon is a natural immune system biochemical and is injected directly into the warts. However, its effectiveness has been challenged, and it often produces side effects including flu-like symptoms (McDermott-Webster, 1999). Imiquimod is a topical treatment that a patient can apply to external genital warts at home. It stimulates the immune system to produce interferon and other immune factors to fight warts (Lamb, 2001). Imiquimod seems to produce fewer and milder side effects than other treatments (HPV Treatment and Prevention Resource, 2001).

HPV and Cancer

It is estimated that in 2001 there will be about 12,900 new cases of invasive cervical cancer in the United States, which will result in about 4,400 deaths (ACS, 2000). Worldwide, about 400,000 new cases are diagnosed each year (NCI, 1999a). The median age of diagnosis for cervical cancer for all races is 48 years (Kiviat, et al., 1999).

Due largely to routine screening using Pap tests, the number of deaths attributed to cervical cancer in the United States dropped 45 percent between the periods 1972-1974 and 1992-1994, and the number of cases declined 43 percent between 1973 and 1995 (NCI, 1999a). The five-year survival rate is nearly 100 percent for pre-invasive cervical cancer, and 91 percent for early invasive cancer. The overall five-year survival rate for all stages of cervical cancer is about 70 percent (ACS, 2000).

African-Americans experience a disproportionate number of deaths from cervical cancer. The death rate is 6.7 per 100,000 for black women, compared to 2.5 per 100,000 for white women (NCI, 1999a). Latinas and Native Americans also have cervical cancer death rates that are above average (ACS, 2000).

Since the late 1800s, researchers have suspected that cervical cancer was sexually transmitted. Medical reports noted that nuns and virgins were not likely to have cervical cancer, and that women who were married to men who traveled a great deal or who had previous wives who died of cervical cancer were more likely to develop cervical cancer ("The Cervical Cancer Virus," 1995). Today, certain types of HPV have been established as causal agents in the development of the cellular changes that may lead to cervical cancer (Janicek & Averette, 2001). An international study found that HPV was present in 93 percent of cervical cancer tumors. HPV 16 was found in 50 percent of the cases, HPV 18 accounted for 14 percent, HPV 45 for eight percent of cases, HPV 31 for five percent , and other HPV types accounted for 23 percent of all cases (Bosch, et al., 1995).

Even though HPV is considered a cause of cervical cancer, only one out of 1,000 women with HPV develops invasive cervical cancer (ACOG, 2000). Most HPV infection never leads to the development of cervical cancer - even in the absence of medical intervention - and treating precancerous cervical lesions detected by Pap tests has greatly reduced the rate of invasive cervical cancer (Ho, et al., 1998; NCI, 1999a).

HPV appears to be necessary, but not sufficient, to the development of cervical cancer. Besides HPV type, researchers believe there are several cofactors that may contribute to the development of cervical cancer. These may include smoking, HIV infection, diet, hormonal factors, and the presence of other sexually transmitted infections, such as chlamydia and/or herpes simplex virus 2 (Anttila, et al., 2001; CDC, 1999; NCI, 1999b).

Certain types of genital HPV are also now considered to be a cause of most cancers of the vagina, vulva, anus, and penis. Although each of these cancers occurs less frequently than does cervical cancer, taken together they equal nearly half the number of cases of cervical cancer in the U.S. (Eng & Butler, 1997). The average age for diagnosis of these cancers is significantly later than for cervical cancer. The median age of diagnosis for vaginal cancer is 67 years and 70 years for vulvar cancer. Anal cancer is typically diagnosed at 66 years of age for women and 63 years for men, and the average age of diagnosis for cancer of the penis is 66 years (Kiviat, et al., 1999). As is the case with cervical cancer, HPV 16 and HPV 18 are most often associated with vaginal, vulvar, anal, and penile cancers (Eng & Butler, 1997). An association has also been made between HPV and oral, head, and neck cancers, although further research needs to be conducted to establish a causal relationship (Mork, et al., 2001; Schwartz, et al., 1998). Men are three times more likely than women to develop head and neck cancers (HPV Treatment and Prevention Resource, 2001).


Abstinence or lifelong monogamy are the most effective ways to avoid HPV infection. However, for most sexually active women, the most important preventive measure women can take to protect themselves from developing cervical cancer is having regular Pap tests (Janicek & Averette, 2001). Avoiding skin-to-skin contact with someone with HPV is the most effective strategy to prevent HPV infection. And although condoms may not eliminate the risk of transmitting HPV, the CDC recommends them for risk reduction (CDC, 2001). Since HPV sheds beyond the covered area, however, condoms do not provide as complete protection as they do for some other pathogens, such as HIV and gonorrhea (Stone, et al., 1999). The claims of condom-use opponents who suggest that condom use leads to increased numbers of HPV infections are false and alarmist. Condom use cannot be blamed for the high prevalence of HPV infection or the incidence of cervical cancer among women in the U.S.

Vaccines against HPV are currently being developed but are still years away from being available (HPV Treatment and Prevention Resource, 2001). Both prophylactic vaccines that prevent HPV infection (most vaccines being developed target HPV 16) and therapeutic vaccines designed to prevent the development of precancerous cells are being developed. Other vaccines in development are both prophylactic and therapeutic in nature (Austell, 2000).

While HPV is endemic among sexually active women and men in the U.S., it is reassuring to know that these infections most often remain asymptomatic and symptoms, if they occur, are usually manageable. Equally reassuring is the fact that condom use is likely to reduce the risk of infection. To reduce the risk of developing the most dangerous conditions associated with HPVs, women and men who are sexually active should have annual physical checkups including evaluation of any symptoms of sexually transmitted infections. Sexually active women should be sure to have an annual Pap test as well.

Additional Resources

American Social Health Association (ASHA)
P.O. Box 13827
Research Triangle Park, NC 27709
(919) 361-8400
(919) 361-8425 (fax)

American Cancer Society (ACS)
1599 Clifton Rd. NE
Atlanta, GA 30329
(404) 329-7530

National Center for HIV, STD, & TB Prevention
Centers for Disease Control and Prevention
Atlanta, GA 30333
Toll-free voice information: 888-232-3228
CDC STI Hotline: 800-227-8922

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Current as of November 2001