HPV (Human Papillomavirus) Infection
HPV (Human Papillomavirus) Infection
Disease History, Characteristics, and Transmission
Introduction
The human papillomavirus (HPV) grows exclusively in the epithelial cells making up the surface of the skin, including the cervix, vagina, and anus. While HPV infection often causes no symptoms, it sometimes triggers benign tumors known as papillomas or warts on the hands and feet, or in the genital area. Most HPV infections clear up on their own, but they are also capable of causing cancers in the cervix and, more rarely, in the vagina, vulva, penis, and anus. The link between HPV and cancer is not well understood, but the virus could trigger abnormal growth and multiplication in the cells it infects. The genetic material (DNA) of HPV has been found in the majority of cervical cancers studied and the disease is a major killer of women in certain parts of the world. However, there is now a vaccine that can protect girls and young women against the main types of HPV causing both genital warts and cervical cancer.
Disease History, Characteristics, and Transmission
Over 100 types of HPV have been identified—about 60 of them cause skin warts, while another 40 or so cause genital warts. Most people with HPV infection will not have symptoms, although they can still transmit the infection to others. Skin warts are either flat (shallow) or plantar (deep), occurring mainly on the hands and feet in children and young adults. Sometimes papillomas grow in the mouth or on the larynx (voicebox). Anogenital warts can occur anywhere in the external genitalia, in the vagina, on the cervix, or around the anus. They consist of soft, moist, pink or flesh-colored swellings. In an otherwise healthy person, these warts are benign. Ninety percent of anogenital warts are caused by HPV type 6 or HPV type 11.
HPV can also cause cervical cancer, with HPV type 16 or HPV type 18 being involved in around 70% of cases. Microscopic evaluation of cells from the cervix taken in a Pap test (a routine screen for cervical cancer) can reveal a series of changes that may lead to cervical cancer. The first stage is known as dysplasia, an abnormality that often reverts to normal by the time a second test is taken. However, these changes may progress to a condition known as cervical intraepithelial dysplasia (CIN), which is generally regarded as being precancerous and likely to develop into cervical cancer within ten years, if left untreated. Most genital HPV infections do not develop into cervical cancer, however.
HPV infection is transmitted by skin contact and, in the case of genital warts, through sexual contact, usually involving intercourse. Rarely, a mother can transmit an HPV infection to her newborn baby, who may then develop warts in the throat or larynx.
WORDS TO KNOW
DYSPLASIA: Abnormal changes in tissue or cell development.
MORTALITY: Mortality is the condition of being susceptible to death. The term “mortality” comes from the Latin word mors, which means “death.” Mortality can also refer to the rate of deaths caused by an illness or injury, i.e., “Rabies has a high mortality.”
PREVALENCE: The actual number of cases of disease (or injury) that exist in a population.
SEXUALLY TRANSMITTED DISEASE (STD): Sexually transmitted diseases (STDs) vary in their susceptibility to treatment, their signs and symptoms, and the consequences if they are left untreated. Some are caused by bacteria. These usually can be treated and cured. Others are caused by viruses and can typically be treated but not cured. More than 15 million new cases of STD are diagnosed annually in the United States.
Scope and Distribution
Infection with HPV is very common around the world. It is estimated that 50–75% of all those who have ever had sexual intercourse will have HPV infection at some time in their lives, although this will usually not cause symptoms. About 1% of sexually active men and women have genital warts. A recent study for the Centers for Disease Control and Prevention (CDC) revealed that the prevalence of HPV infection among women aged 14–59 in the United States is probably higher than previously estimated. Vaginal swabs were tested for the presence of HPV DNA and found to be positive in 27% of the group. In women aged 20–24, the rate of HPV infection was 44.8% and in the 14–24 age group, the rate was 33.8%. When the infections were analyzed by HPV type, 3.4% of the women were infected with type 6, 11, 16, and 18, which are responsible for the majority of genital warts and cervical cancer. If extrapolated to the whole U.S. population, this study suggests that the number of HPV infections among women aged 14–59 is 7.5 million, rather than the 4.5 million previously estimated.
Men also can get HPV and, for both sexes, the risk of infection goes up as the number of sexual partners increases. Having sex with someone who has had many sexual partners is also risky. In other words, the risk of HPV goes up with the number of possible exposures to the virus.
Globally, HPV infection exacts a significant toll in the form of cervical cancer. One in ten of all cancers in women, worldwide, are cervical cancer. It is the most commonly diagnosed cancer among women in southern Africa and Central America. The disease causes more than 273,000 deaths every year, accounting for 9% of cancer mortality in women.
Treatment and Prevention
Often, no treatment is needed for the symptoms of HPV infection, because both skin and genital warts tend to disappear over time. Ninety percent are gone within two years. If warts are large or painful, they can be destroyed by burning (electrocautery), freezing (cryotherapy), and chemical treatment. Laryngeal papillomas can be surgically removed.
Sexual abstinence is the only sure way of avoiding genital HPV infection. Limiting the number of sexual contacts and using condoms will provide some protection. Women who are sexually active should have regular Pap smears to check for the early signs of cervical cancer. In countries that have a national screening program, cervical cancer has become far less common than previously and cases tend to occur among women who have never had a Pap test. Finally, a vaccine against HPV types 6, 11, 16 and 18 has recently (2006) become available.
IN CONTEXT: SOCIAL AND PERSONAL RESPONSIBILITY
The Division of Sexually Transmitted Disease (STD) Prevention of the Centers for Disease Control (CDC) states that “the surest way to eliminate risk for genital HPV infection is to refrain from any genital contact with another individual.”
For individuals who take the risks of sexual activity the CDC states that “a long-term, mutually monogamous relationship with an uninfected partner is the strategy most likely to prevent future genital HPV infections. However, it is difficult to determine whether a partner who has been sexually active in the past is currently infected.”
The CDC further recommends that “for those choosing to be sexually active and who are not in long-term mutually monogamous relationships, reducing the number of sexual partners and choosing a partner less likely to be infected may reduce the risk of genital HPV infection. Partners less likely to be infected include those who have had no or few prior sex partners.”
With regard to condom use, the CDC states “HPV infection can occur in both male and female genital areas that are covered or protected by a latex condom, as well as in areas that are not covered. While the effect of condoms in preventing HPV infection is unknown, condom use has been associated with a lower rate of cervical cancer, an HPV-associated disease.”
SOURCE: Centers for Disease Control and Prevention, Division of Sexually Transmitted Disease (STD)
IN CONTEXT: TRENDS AND STATISTICS
The Division of Sexually Transmitted Disease (STD) Prevention of the Centers for Disease Control (CDC) states that “every year, about 5.5 million people acquire a genital HPV infection. While there is no way to know for sure if HPV is increasing, there are no signs of a significant decline. With improved testing technology, researchers have been able to get a much clearer picture of the true extent of HPV in certain groups in recent years, and the infection is even more common than originally asserted.”
SOURCE: Centers for Disease Control and Prevention, Division of Sexually Transmitted Disease (STD)
Impacts and Issues
Gardasil®, the HPV vaccine, was approved for use in the United States in June 2006, and is recommended for use in girls aged 11–12. The vaccine has been shown to be safe and effective in female saged 9–26. Research is ongoing into whether the vaccine works for older women and boys, and how long the protection lasts. The vaccine is made from the proteins that compose the outer coat of the HPV virus. Research has shown that it affords the highest level of protection against genital warts and cervical cancer among those who have not been exposed to HPV infection already— that is, those who have not become sexually active. Females who have been exposed may gain some protection, but the vaccine cannot cure any existing infection. It is important for those who have been vaccinated to still receive regular Pap tests, because the current vaccine does not protect against all the HPV types that can cause cervical cancer. If Pap screening and the HPV vaccine became available worldwide, it is possible that cervical cancer might be eradicated.
In early 2007, Texas Governor Rick Perry issued an executive order requiring HPV vaccination for all schoolgirls entering the sixth grade for the 2008–2009 school year. With this order, Texas became the first state to require vaccination against HPV. The governor's order was intended to bypass political objections in the state legislature and local some communities, including objections by parents’ groups to giving young girls a vaccine that prevents a complication of a sexually transmitted disease before the girls become sexually active. Perry also ordered Texas health agencies to provide the vaccine free or at a reduced cost to girls without health insurance, as well as to those without health coverage for routine vaccinations. As of April 2007, the state legislature was considering a new bill that would remove the HPV vaccine from the list of required vaccinations for Texas school children, and the debate about mandatory HPV vaccination remains unresolved.
See AlsoCancer and Infectious Disease; Sexually Transmitted Diseases.
BIBLIOGRAPHY
Books
Wilson, Walter R., and Merle A. Sande. Current Diagnosis & Treatment in Infectious Diseases. New York: McGraw Hill, 2001.
Periodicals
Dunne, E.F., et al. “Prevalence of HPV Infection Among Females in the United States.” Journal of the American Medical Association 297 (February 28, 2007): 813–819.
Web Sites
American Cancer Society. “Frequently Asked Questions About Human Papilloma Virus (HPV) Vaccines.” <http://www.cancer.org/docroot/CRI/content/CRI_2_6x_FAQ_HPV_Vaccines.asp> (accessed February 25, 2007).
Cancer Research UK. “Cervical Cancer. International
Statistics.” <http://info.cancerresearchuk.org/cancerstats/types/cervix/international/> (accessed February 25, 2007).
Centers for Disease Control and Prevention. “Genital HPV Infection—CDC Fact Sheet.” May 2004. <http://www.cdc.gov/std/hpv/STDFact-HPV.htm> (accessed February 25, 2007).
Susan Aldridge