Human Papillomavirus, or HPV, is a widespread virus that most sexually active individuals will encounter at some point in their lives. With more than 200 strains, it is the most common sexually transmitted infection in the United States. Approximately 42 million Americans are currently infected with types of HPV known to cause disease, with about 13 million new infections occurring annually. The vast majority of these infections, about nine out of ten, are cleared by the body’s immune system within two years and cause no lasting health issues.
However, some infections persist and can lead to health complications. These viruses are categorized as either low-risk or high-risk depending on their potential to cause disease.
HPV Transmission and Health Risks
Human Papillomavirus is highly contagious and spreads primarily through intimate skin-to-skin contact. This includes vaginal, anal, and oral sex, as well as genital-to-genital and hand-to-genital contact. It’s also possible, though less common, for the virus to spread from a pregnant person to their baby during delivery or through contact with contaminated objects.
The various strains of HPV are broadly classified into two groups: low-risk and high-risk. Low-risk strains, such as HPV types 6 and 11, are responsible for approximately 90% of all genital warts. These warts can appear as small, cauliflower-like bumps on the genital or anal areas and, while uncomfortable, are not associated with cancer.
Persistent infections with high-risk HPV strains, however, can lead to the development of cancer over many years. There are at least 14 high-risk strains, with HPV types 16 and 18 being the most common, accounting for about 70% of all invasive cervical cancers. These high-risk types are also linked to cancers of the anus, vagina, vulva, penis, and oropharynx, which includes the back of the throat, base of the tongue, and tonsils. It is estimated that HPV is responsible for about 91% of anal cancers and 70% of oropharyngeal cancers.
An infection with a high-risk HPV type often does not produce any initial symptoms. The virus can cause changes in the cells it infects, a process that can take 5 to 10 years to develop into precancerous cells. If not detected and treated, these changes can progress to cancer over a period of about 20 years. Factors that can increase the likelihood of a high-risk HPV infection persisting and leading to cancer include having a weakened immune system or smoking.
Prevention Through Vaccination
Vaccination is the primary method of preventing HPV-related health issues. The vaccine stimulates the body to produce antibodies that fight the virus upon future exposure. The currently available vaccine in the U.S., Gardasil 9, protects against nine HPV types: 6, 11, 16, 18, 31, 33, 45, 52, and 58.
For maximum effectiveness, the vaccine series should be administered before an individual becomes sexually active. The Centers for Disease Control and Prevention (CDC) recommends routine vaccination for both boys and girls at age 11 or 12, though the series can be started as early as age 9. A two-dose schedule is recommended for those who start the vaccination series before their 15th birthday, with the second dose given 6 to 12 months after the first.
Individuals starting at age 15 or older require a three-dose schedule. Catch-up vaccination is recommended for everyone through age 26 who was not adequately vaccinated when younger. Some adults between 27 and 45 may get the vaccine after discussing their risk of new infection with their healthcare provider.
The HPV vaccine has a well-established safety profile, confirmed by over 15 years of monitoring and extensive safety testing before FDA licensure. The most common side effects are mild and include pain, redness, or swelling at the injection site. The vaccine’s protection is long-lasting, with studies showing effectiveness for more than 10 years without any evidence of waning protection.
Screening and Early Detection
Screening for HPV-related disease focuses on detecting cellular changes on the cervix before they can develop into cancer. There are two primary tools used for cervical cancer screening: the Pap test and the HPV test. The Pap test, or Pap smear, involves collecting cells from the cervix to be examined under a microscope for any abnormalities.
The HPV test detects the DNA of high-risk HPV strains in cervical cells. This test can identify the presence of the virus even before any cellular changes are visible. Guidelines from organizations like the U.S. Preventive Services Task Force (USPSTF) and the American Cancer Society (ACS) provide recommendations on who should be screened and how often.
Current recommendations suggest that individuals with a cervix begin screening at age 25. The preferred screening strategy is a primary HPV test every five years. If primary HPV testing is not available, other options include a co-test, which combines an HPV test and a Pap test, every five years, or a Pap test alone every three years. Screening is generally recommended to continue through age 65.
Individuals who have had a total hysterectomy (removal of the uterus and cervix) for non-cancerous reasons do not need to continue screening. However, those with a history of a serious precancerous lesion should continue testing for at least 25 years after its detection, even if this extends beyond age 65. Similarly, individuals with a weakened immune system may require a more frequent screening schedule as advised by their healthcare provider.
Managing HPV-Related Conditions
While there is no treatment for the HPV virus, the health conditions it causes can be managed. When needed, treatment addresses the specific conditions caused by the virus, like genital warts or abnormal cell changes.
Genital warts can be treated with a variety of methods. These include:
- Topical prescription creams like imiquimod, which helps the body’s immune system fight the warts, or podofilox, which destroys the wart tissue.
- Chemical treatments applied by a healthcare provider, such as trichloroacetic acid, to burn off the warts.
- Cryotherapy, which freezes the warts with liquid nitrogen.
- Surgical removal of the warts.
If screening tests reveal abnormal cells on the cervix, a colposcopy is often the next step. During this procedure, a provider uses a magnifying instrument to examine the cervix and may take a small tissue sample, or biopsy, for further examination. If precancerous cells must be removed, procedures like the Loop Electrosurgical Excision Procedure (LEEP), cryosurgery, or a cold knife cone biopsy are available. These treatments use an electric current, freezing, or surgical removal, respectively, and are highly effective at preventing cervical cancer.