What are human papillomaviruses (HPVs)?

There are over 100 types of papillomaviruses (HPVs) that infect humans. Of these, more than 40 types can infect the anogenital tract (genital tract and anus) of men and women and cause genital warts (known as condylomata acuminata or venereal warts). A subgroup of the HPVs that infect the anogenital tract (genital tract and anus) can lead to precancerous changes in the uterine cervix and cause uterine, cervical cancer. HPV infection also is associated with the development of other anogenital cancers in women. The HPV types that cause cevical cancer also have been linked with both anal and penile cancer in men as well as a subgroup of head and neck cancers in both women and men. Genital warts and HPV infection are transmitted primarily by sexual intimacy, and the risk of infection increases as the number of sexual partners increase.

The most common HPV types that infect the anogenital tract are HPV types 6, 11, 16, and 18 (HPV-6, HPV-11, HPV-16, and HPV-18), although other HPV types can also infect the anogenital tract. Among these, HPV-6 and HPV-11 are most commonly associated with benign lesions such as genital warts and mild dysplasia of the cervix (potentially precancerous changes in the appearance of cervical cells under a microscope) and are termed "low-risk" HPV types. In contrast, HPV-16 and HPV-18 are the types found in the majority of cervical and anogenital cancers as well as severe dysplasia of the cervix. These belong to the so-called "high-risk" group of HPVs.
Other, different HPV types infect the skin and cause common warts elsewhere on the body. Some types of HPVs (e.g., HPV 5 and 8) frequently cause skin cancers in people who have a condition known as epidermodysplasia verruciformis.

HPV Symptoms and Tests

Genital HPV infection is very common. At least half of people who have had sex will contract the HPV virus (human papillomovirus) at some point in their lives. Yet many will not know it because they will not have any HPVsymptoms.
Whether HPV symptoms occur or not can depend on the HPV type involved in the infection. There are more than 100 types of HPV. Some HPV types are associated with genital warts, although the warts are not always visible.

Some types of HPV are associated with cervical and other cancers, and no warts occur, and no other symptoms may be noticed. Some HPV types also cause common warts that you can find on other areas of the body such as your hands or feet.
Many people who get genital HPV will clear it without treatment and without symptoms, and no health problems will occur. The longer the virus is in the body, however, the higher your risk of developing health problems such as cervical cancer or anal cancer.

Here's what you need to know about genital HPV infection, HPV symptoms, and the HPV test:

HPV Symptoms

The HPV virus lives in mucous membranes, such as those in the genital area, or on the skin. If genital warts show up, it's an indication of HPV infection. Genital warts take on many different appearances. They can be raised, flat, pink, or flesh-colored. They can even be shaped like cauliflower. Sometimes there is a single wart; other times multiple warts appear. They can be small or large. They can be on the anus, cervix, scrotum, groin, thigh, anus, or the penis.
Genital warts can show up weeks or even months after sexual contact with a person infected with HPV virus. That person may not know he or she is infected and is responsible for HPV transmission.

Some types of genital HPV infection are associated with cancer, including cervical cancer and cancer of the vulva, anus, or penis. If infection occurs with one of these virus types, precancerous changes can occur in cells in the tissue without causing any symptoms.

How Is HPV Infection Diagnosed?

The appearance of genital warts is one way HPV infection is diagnosed. A doctor simply does a visual inspection. The HPV types associated with warts, however, are not generally the types associated with cancer.
Women infected with the type of HPV that can cause cancer may first be told their Pap test results are abnormal. Pap tests are the main way doctors find cervical cancer or precancerous changes in the cervix.
To find out for sure if the changes are related to HPV, a doctor may decide to perform a DNA test on the virus in women who have an abnormal Pap smear. This tells you and your doctor whether the HPV virus you have can cause cancer. Only certain strains of HPV cause cancer. Indeed, HPV 16 and 18 account for 70% of all cervical cancers. This DNA test is often given to women who have mild Pap test abnormalities. It may also be given as part of a routine Pap test to women over age 30.

In the HPV test, a doctor takes a swab of cells from the cervix, just as for the Pap test. The cells are then analyzed in the laboratory. The test can identify 13 of the high-risk HPV types associated with cervical cancer.

This test is rarely given routinely to women under 30 because so many younger women are exposed to HPV and their bodies typically clear the infection without treatment. The DNA test could cause unnecessary worry and concern. Some experts also believe that in younger women the cervix is more susceptible to the HPV virus and that as women get older the cervix may become less susceptible.
In men, as in women, genital warts reflect HPV infection. But no specific test for the strains of HPV that cause cancer is available at this time for men.

When Is the Best Time to Test?

Combining the Pap test with the HPV test is appropriate for women aged 30 and over, according to the American College of Obstetricians and Gynecologists.
This test helps women and their doctors learn if a woman is at high risk or low risk for developing cervical cancer. If the HPV test is positive, the doctor can then decide if more testing is needed. One test that may be ordered next is a colposcopy, in which a special magnifying device is used to examine the cervix, vagina, and vulva.
If a woman is trying to get pregnant, there's no need to have the HPV test unless her doctor orders it based on an abnormal Pap test. During the first prenatal visit, a Pap smear is taken, and if the results are suspicious of HPVinfection, the doctor can order the HPV test then.

HPV and other cancers

Some types of HPV can increase your risk of developing cancers in other parts of the body, not just the cervix. Not everyone with these types of HPV will go on to develop cancer. These cancers are rare and other factors are necessary before cancer will develop.

History of papillomavirus research

Papillomavirus research has passed through several phases. The field began slowly with the experimental transmission of human and animal warts prior to 1930. Greater interest in these viruses was stimulated in the 1930s by the demonstration that filtered extracts from cutaneous papillomas of wild cottontail rabbits could induce lesions with malignant potential in cottontail and domestic rabbits. Although investigations in the 1930s and 1940s were limited to in vivo studies in outbred rabbits, many principles of papillomavirus biology were estab­lished by observations made during this period.

The availability of infectious extracts permitted the reproducible induction of lesions whose natural history could be followed or be experimentally modified. Interest in papillomaviruses diminished during the 1950s and 1960s. This change was attributable to several factors, including the inability of papillomaviruses to propagate in culture at a time when the life-cycle and transforming activity of other oncogenic viruses could be studied in vitro, permitting rapid advances in molecular understanding of these processes in the more tractable systems. In addition, human papillomaviruses (HPV) were believed to have limited medical importance because the conditions they induced were thought to be limited to benign lesions with little or no potential for malignant progression.

The advent of molecular cloning during the 1970s led to a resurgence in papillomavirus research. As in other areas of biology, this technical revolution was critical to progress in the investigation of papillomaviruses. The unlimited availability of wild-type and mutant viral genomes made it possible to study the function of viral genes and their products, to use viral sequences as molecular probes to detect papillomavirus sequences in tissue, and to identify and molecularly clone new viral genotypes. Application of these molecular techniques led to the identification of HPV as the necessary infectious cause of a major public health problem, cervical cancer. These studies also provided insight into the pathogenesis of HPV-induced disease, established new paradigms for cellular transformation by viral genes, and identified candidate antigens for protection against papillomavirus infection.