Human Papillomavirus (HPV) is a widespread virus. Certain strains are categorized as “high-risk” (hrHPV) due to their ability to cause various cancers. While many HPV infections are temporary and clear on their own, high-risk types can persist and lead to cellular changes. Understanding high-risk HPV involves recognizing its characteristics, the diseases it can cause, and available screening, management, and protection strategies.
What Makes HPV High-Risk
High-risk HPV types are distinguished by their oncogenic potential, meaning they can lead to cancer. This occurs when the virus integrates its DNA into the host cell’s genome, disrupting normal cellular functions and promoting uncontrolled cell growth. Approximately 14 types of HPV are classified as high-risk, with HPV 16 and HPV 18 being the most prevalent, responsible for about 70% of HPV-related cancers globally. Other notable high-risk types include HPV 31, 33, 45, 52, and 58.
Transmission of high-risk HPV primarily occurs through intimate skin-to-skin contact, most commonly during vaginal, anal, or oral sex. The virus infects the thin, flat squamous cells lining the moist surfaces of organs and body cavities, such as the cervix, anus, mouth, and throat. Most high-risk HPV infections are asymptomatic, meaning they produce no noticeable symptoms, and the body’s immune system typically clears the virus within two years. However, if the infection persists, it can lead to precancerous changes.
Diseases Caused by High-Risk HPV
Persistent infection with high-risk HPV types can lead to the development of several cancers and precancerous conditions. Cervical cancer is the most well-known and common cancer linked to HPV, with nearly all cases attributed to these high-risk strains. The virus causes changes in cervical cells, which can progress from precancerous lesions to invasive cancer if not detected and treated.
Beyond cervical cancer, high-risk HPV is also associated with other cancers. These include anal cancer (over 90% of cases linked to HPV), and oropharyngeal cancers (about 70% of cases, specifically in the back of the throat, tonsils, and base of the tongue). High-risk HPV can also cause vaginal cancer (about 75% of cases), vulvar cancer (about 70% of cases), and penile cancer (about 60% of cases).
Screening and Managing High-Risk HPV
Detecting high-risk HPV and the cellular changes it causes primarily involves two screening methods: the Pap test (cytology) and the HPV DNA test. A Pap test examines cervical cells for abnormalities, while an HPV DNA test specifically identifies the presence of high-risk HPV types, including HPV 16 and 18. These tests are often used together in co-testing for individuals aged 30 and older, or an HPV test may be used as a primary screening method.
If a high-risk HPV result is positive, it signifies an increased risk for developing precancerous lesions or cancer, but it does not mean cancer is present. Management typically involves monitoring through more frequent follow-up testing, such as repeat Pap tests or HPV DNA tests, or a procedure called colposcopy. During a colposcopy, a healthcare provider uses a magnifying device to examine the cervix more closely and may take biopsies of any suspicious areas. If precancerous lesions are found, procedures like a Loop Electrosurgical Excision Procedure (LEEP) or cryotherapy may be performed to remove the abnormal cells, managing the cellular changes even though there is no direct “cure” for the virus itself.
Protecting Against High-Risk HPV
The most effective strategy for preventing high-risk HPV infection is vaccination. The HPV vaccine, such as Gardasil 9, protects against the most common high-risk types, including HPV 16 and 18, as well as other cancer-causing and low-risk types that cause genital warts. The vaccine is recommended for routine vaccination at ages 11 or 12, though it can be started as early as age 9. For individuals initiating the series before their 15th birthday, two doses are typically sufficient, given 6 to 12 months apart, offering close to 100% efficacy against vaccine-type related persistent infections.
Vaccination is also recommended for individuals through age 26 if they were not adequately vaccinated when younger. Some adults aged 27 through 45 years may also consider vaccination after discussion with their clinician, although benefits may be less due to prior exposure. While vaccination offers strong protection, other measures, such as condom use, can reduce the risk of HPV transmission. Condoms do not offer complete protection, as HPV can spread through skin-to-skin contact in areas not covered.