Infection: HPV Infection

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Infection: HPV Infection

Causes and Symptoms
The Future
For more information


HPV infection is a sexually transmitted disease (STD) caused by thirty to forty of the 130 or so known strains of human papillomavirus, the name of a group of viruses that infect the skin and mucous membranes of humans and some animals. In humans these sexually transmitted strains can cause genital warts, precancerous changes in the tissues of the female vagina, or cervical cancer. Other strains of HPV are responsible for warts on the soles of the feet (plantar warts), common warts on the hands, and flat warts on the face or legs.


HPV infection is one of the most common sexually transmitted diseases in the United States. Most people who are infected with one of the sexually transmitted strains of the virus, however, do not know that they have it because they have no symptoms. They can easily transmit the infection to a partner.

The various strains of HPV are classified as either low-risk or high-risk according to their potential for causing cancer or other serious health

problems. Low-risk strains of HPV may produce genital warts but do not cause cancer. Low-risk types 6 and 11 are responsible for 90 percent of cases of genital warts. High-risk strains of the virus, which include types 16, 18, 31, and 45, may cause cervical cancer in women as well as cancers of the anus and penis in men. These high-risk strains can also cause cancer of the mouth and throat in people who have oral sex. HPV types 16 and 18 are found in more than 70 percent of cervical cancers in women.


In recent years HPV infection has become one of the most common STDs in the United States. Approximately 20 million Americans were infected with HPV as of 2008, and another 6.2 million people become newly infected each year. According to one study, 27 percent of women between the ages of fourteen and fifty-nine are infected with one or more types of HPV. The Centers for Disease Control and Prevention (CDC) estimates that more than 80 percent of American women will contract at least one strain of genital HPV by age fifty. About 75–80 percent of sexually active Americans of either sex will be infected with HPV at some point in their lifetime.

As far as is known, men and women are at equal risk of being infected with HPV, as are members of all races and ethnic groups.

Some people are at greater risk of sexually transmitted HPV than others:

  • Gay and bisexual men.
  • People with HIV or other diseases that weaken the immune system.
  • Males or females below age twenty-five. Younger people appear to be more biologically vulnerable to the HPV virus.
  • People who have large numbers of sexual partners.
  • People in relationships with partners who have sex with many other people.

In terms of specific illnesses associated with HPV, 11,000 women are diagnosed with cervical cancer each year in the United States and 3,900 women die annually of the disease. Another 5,800 women are diagnosed with cancers of the vagina and the external female genitals, while 3,300 men are diagnosed with cancer of the penis or the anal area. The risk of anal cancer is seventeen to thirty-one times higher among gay and bisexual men than among heterosexual men.

Causes and Symptoms

The cause of sexually transmitted HPV infection is one or more strains of the human papillomavirus. The virus enters the body through small breaks in the skin surface or in the mucous membranes lining the genitals. In most cases the body fights off the virus within a few weeks. In some people, however, HPV remains dormant for a period ranging from a few weeks to several years in one of the lower layers of skin cells. The virus then begins to replicate (copy itself) when these cells mature and move upward to the surface of the skin. The virus affects the shape of the cells, leading to the formation of noticeable warts, precancerous changes in skin cells, or cervical cancer. About 1 percent of sexually active adults in the United States have genital warts at any one time; about 10 percent of women with high-risk HPV in the tissues of their cervix will develop long-lasting HPV infections that put them at risk for cervical cancer.

Symptoms of sexually transmitted HPV infection may include:

  • Genital warts. These appear as bumps or clusters of fleshy outgrowths around the anus or on the genitals. Some may grow into larger cauliflower-shaped masses. Genital warts usually appear within weeks or months after sexual contact with an infected person. If left untreated, genital warts may go away, remain unchanged, or increase in size or number but will not turn into cancers. It is possible, however, for a person to be infected with a high-risk strain of HPV as well as one of the strains that cause genital warts; therefore the appearance of genital warts does not necessarily mean that the person is not at risk of cancer.
  • Precancerous changes in the tissues of the female cervix. These are flat growths on the cervix that cannot be seen or felt by the infected woman.
  • Cancer. High-risk strains of HPV can cause cancers of the mouth and throat as well as cancers of the anal area and the male and female genitals. These typically take years to develop after infection. In men, symptoms of anal cancer may include bleeding, pain, or a discharge from the anus, or changes in bowel habits. Early signs of cancer of the penis may include thickening of the skin, tissue growths, or sores.


There is no general blood, urine, or imaging test for HPV infection. The diagnosis of genital warts is obvious based on their location and appearance. The doctor may, however, use a vinegar solution to identify HPV-infected areas on the skin of the genitals. The vinegar solution may turn white if HPV is present. Since genital warts are caused by low-risk strains of HPV, the doctor does not need to identify the specific strain of the virus that is present.

Sexually active women should be screened periodically for the presence of changes in the tissues of the cervix. The most common test is the Papanikolaou test or Pap smear, invented by a Greek physician in the 1940s. To perform a Pap smear, the doctor takes a small spatula to obtain cells from the outer surface of the cervix and smears the collected cells on a slide that is then examined in a laboratory for signs of any abnormal cells. If abnormal or questionable cells are found, the doctor may order an HPV DNA test, which can identify the DNA of 13 high-risk types of HPV in cells taken from the cervix.

There are no HPV screening tests for men.


Patients with genital warts should never use over-the counter-preparations designed to remove common or flat warts from the hands or face.

Doctors can treat genital warts with various medical or surgical techniques:

  • Cryotherapy. Cryotherapy uses liquid nitrogen to freeze the warts. The dead tissue in the wart falls away from the skin beneath in about a week.
  • Imiquimod. Imiquimod is a topical cream that gets rid of genital warts by stimulating the body's immune system to fight the virus that causes the warts.
  • Podofilox. This is a topical medication available in liquid or gel form that destroys the wart tissue.
  • Surgery. The doctor can remove the wart by drying it out with an electric needle and then scraping the tissue with a sharp instrument called a curette. Lasers can also be used to remove genital warts.

Low-grade precancerous changes in the tissue of the female cervix are not usually treated directly, because most of them will eventually go away on their own without developing into cancer. The patient should, however, see the doctor for follow-up Pap smears to make sure that the tissues are returning to normal. High-risk precancerous lesions are removed, usually by surgery, cryotherapy, or laser surgery.


Cervix: The narrow neck or outlet of a woman's uterus.

Cryotherapy: The use of liquid nitrogen or other forms of extreme cold to treat a skin disorder.

Mucous membrane: Soft tissues that line the nose, throat, stomach, and intestines.

Pap test: A screening test for cervical cancer devised by Giorgios Papanikolaou (1883–1962) in the 1940s.

Topical: Referring to a type of medication applied directly to the skin or outside of the body.


The prognosis of sexually transmitted HPV infections depends on the patient's age, number of sexual partners, gender, and the condition of their immune system. Women are significantly more likely than men to develop cancers following HPV infection. However, most people of either sex with normally functioning immune systems who are infected with HPV will clear the infection from their bodies within two years.


Preventive measures that people can take to lower their risk of HPV infection include:

  • Abstaining from sex, or having sex only with an uninfected partner who is faithful.
  • Reducing the number of sexual partners.
  • Using condoms regularly during sexual intercourse.
  • For women, using a new vaccine called Gardasil. Approved by the Food and Drug Administration in 2006, Gardasil is a vaccine that protects against the four types of HPV that cause most cervical cancers and genital warts. The vaccine is recommended for eleven-and twelve-year-old girls. It is also recommended for girls and women age thirteen through twenty-six who have not yet been vaccinated or completed the vaccine series. Gardasil works best in girls who have not yet been sexually active. It is given as a series of three shots over a six-month period.

The Future

Researchers are working on developing vaccines that protect against additional types of the HPV virus. Other scientists are studying the possibility that the transmission of HPV could be prevented by applying substances that would kill bacteria or viruses directly to the skin of the genitals or to condoms. Several different gels and creams were in clinical trials as of 2008.


For more information


Gonzales, Lissette. Frequently Asked Questions about Human Papillomavirus. New York: Rosen, 2007.

Marr, Lisa. Sexually Transmitted Diseases: A Physician Tells You What You Need to Know, 2nd ed. Baltimore, MD: Johns Hopkins University Press, 2007.

Nardo, Don. Human Papillomavirus (HPV). Detroit, MI: Lucent Books, 2007.


Brody, Jane. “Personal Health: HPV Vaccine; Few Risks, Many Benefits.” New York Times, May 15, 2007. Available online at (accessed July 8, 2008).


Centers for Disease Control and Prevention (CDC). Human Papillomavirus (HPV) Infection. Available online at (updated June 30, 2008; accessed July 8, 2008).

Centers for Disease Control and Prevention (CDC) Fact Sheet. HPV and Men. Available online at (updated August 14, 2007; accessed July 8, 2008).

Mayo Clinic. HPV Infection. Available online at (updated March 13, 2007; accessed July 8, 2008).

National Cancer Institute (NCI). Human Papillomaviruses and Cancer: Questions and Answers. Available online at (updated February 14, 2008; accessed July 8, 2008).

National Institute of Allergy and Infectious Diseases (NIAID). Human Papillomavirus and Genital Warts. Available online at (updated February 8, 2007; accessed July 8, 2008).

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Infection: HPV Infection

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