HPV; about 100 types of DNA virus; infecting epithelial cells only; gynecologically important types HPV-6, -11, -16 and -18. Incubation period: 1 - 20 months, 2 - 3 months on average.

Epidemiology. Infections by HPV have been identified most commonly in women between 20 and 24 years of age. Large studies have found that on average more than 40% of all sexually active adolescents are infected with HPV compared with less than half of this percentage for all sexually active women.

If one relies on the presence of visible warts, only about 1% of sexually active teenagers are infected. Using the PAP smear, evidence of cervical infection has been found in 2 - 12%, with the highest rates having been observed in groups of adolescents attending STD clinics. Studies employing a more sensitive diagnostic tool such as DNA hybridization have shown that 9 - 18% of unselected sexually active women have HPV. Finally, using a DNA amplification technique such as PCR, 46% of unselected sexually active women had evidence of infection (

table 11).

Symptoms, Diseases and Sequelae. Most HPV infections are asymptomatic and without clinical manifestations. But a latent infection in one sexual partner may lead to active infection in the other by sexual transmission.

The benign types, HPV-6 and -11, usually infect the ano-urogenital region, causing visible warts that are very painful and connected with high rates of recidivism.

The potentially malignant types HPV-16 and -18, which are far rarer, infect the cervix and are associated with a higher risk for cervical cancer. However, there are no clinical signs of being infected or discomfort.

Moreover, about 90% of young women overcome these asymptomatic infections within 8 - 30 months, and this is not dependent on infection by low- or high-risk type HPV. Identified as having the high-risk HPV type, persistently infected adolescents have an increasing risk of high-grade intraepithelial lesions.

Diagnosis. Visible ano-urogenital warts are diagnosed by inspection. HPV-DNA tests may be indicated to clarify presumptive diagnosis. Histological investigations should be done in cases of pigmented and ulcerating warts.

Cervical anomalies are best screened routinely both by colposcopy under acetic acid application and PAP smear. However, PAP smears are not perfect because of false-negative rates of 20 - 60%. HPV tests are recommended for adolescents in cases of suspicious colposcopic findings and/or abnormal PAP smears (PAPIIw, PAPIII). The available methods are DNA hybridization and DNA amplification PCR techniques, and a new method was recently published that identifies HPV antigens by means of monoclonal antibodies. The latter test proves active HPV infections only.

Histological investigations should be carried out in cases of more than 1 year in adolescence with persistent high-risk types of infection as detected by colposcopic and/or cytologic data. Most reliable results are obtained using a conization specimen.

Treatment. Ano-urogenital warts which do not cause discomfort and may resolve spontaneously should first be observed. During this time girls should avoid sexual intercourse. For treatment, excision of warts by CO2 laser is recommended. Self-treatment locally with podophyllotoxin or imiquimod is not suitable for adolescents because of the risk of noncompliance. None of the available therapeutic methods protect from recidivism of HPV.

In cases of high-risk cervical infections with more than 1 year of persistence in adolescence, reliable data from superficially obtained conization specimens suggest that a decision has to be made about the possibility of an additional surgical procedure. In most cases, the superficial conization itself is sufficient treatment in adolescents.