Human papillomavirus (HPV) is one of the most common sexually transmitted infections globally. There are over 100 strains of the virus, with around 40 strains that can be spread through intimate skin-to-skin contact. While most strains of HPV show no symptoms and will resolve on their own within 1-2 years, some strains are considered high-risk and can lead to cancer or other serious health problems.
What is HPV?
HPV is a viral infection that is passed through intimate skin-to-skin contact. It can be spread through vaginal, anal, and oral sex, but does not require penetration to be transmitted. HPV can also be spread by sharing sex toys. The virus infects epithelial tissues, such as the skin or mucous membranes, and often causes no symptoms at all as the immune system clears the infection. However, for some people HPV can persist and cause health problems.
There are over 100 known strains of HPV, with around 40 strains that are passed through sexual contact. Strains are categorized as either low-risk or high-risk based on their potential to cause cancer. Low-risk HPV strains, such as HPV-6 and HPV-11, can cause genital warts but will not lead to cancer. High-risk HPV strains can cause cell abnormalities that may develop into cancer over time if left untreated.
Common High-Risk HPV Strains
The high-risk HPV strains that are most likely to lead to cancer include:
- HPV 16 and 18 – these two strains cause around 70% of all cervical cancers and can also cause cancers of the anus, penis, vagina, vulva, and back of the throat.
- HPV 31, 33, 45, 52, and 58 – these strains account for around 20% of cervical cancers.
- HPV 35, 39, 51, 56, 59 – these strains are less common causes of cervical cancer.
In addition to cervical cancer, some of these high-risk HPV strains are linked to other types of cancer:
- HPV 16 is linked to cancer of the mouth/throat, anus, penis, and vulva.
- HPV 18 is associated with anal and lung cancers.
- HPV 6 and 11 can cause genital warts and respiratory papillomatosis (warts in the airway).
HPV Transmission and Symptoms
HPV is spread through intimate skin-to-skin contact, usually during vaginal, oral, or anal sex. Using condoms reduces, but does not eliminate, the risk of infection. HPV can infect areas not covered by a condom. The virus can also spread by sharing sex toys.
Most people with HPV will never know they are infected, as the virus often causes no symptoms. When HPV does cause symptoms, these may include:
- Genital warts (cauliflower-like bumps in the genital area caused by low-risk HPV strains).
- Abnormal cells on a Pap smear (cells infected with high-risk HPV).
- Abnormal vaginal bleeding between periods.
- Genital itching.
- Respiratory papillomatosis symptoms like hoarseness (caused by HPV 6 and 11).
Who is Most at Risk for HPV?
HPV is extremely common, with most sexually active adults getting infected at some point. Around 79 million Americans are currently infected. However, certain groups have a higher risk of contracting HPV and associated cancers:
- Women – cervical cancer risk, especially under 30.
- Men who have sex with men – increased anal cancer risk.
- People with weakened immune systems, like those with HIV.
- People who smoke cigarettes.
- Individuals taking oral contraceptives for over 5 years.
The highest rates of HPV infection affect sexually active adolescents and young adults in their late teens to early 20s. The immature cervix in younger women is more vulnerable to HPV infection and abnormal cell changes.
HPV and Cancer
Most HPV infections are cleared by the immune system within 1-2 years without causing health problems. However, sometimes the infection persists and causes cell changes that may gradually develop into cancer. It often takes 10-20 years after initial HPV infection for cancer to develop.
High-risk HPV strains can cause abnormal and precancerous cell changes that, if left untreated, may lead to cancers of the:
- Cervix
- Vulva
- Vagina
- Anus
- Penis
- Mouth/throat
HPV is responsible for over 90% of anal and cervical cancers, over 70% of vaginal and vulvar cancers, and over 60% of penile cancers. It also causes around 70% of oropharyngeal cancers (back of the throat, tonsils, base of tongue).
HPV 16 and 18 account for around 70% of cervical cancers. non-16/18 HPV types like 31, 33, 45, 52 and 58 account for another 20% of cases. The remaining 10% are not linked to HPV.
Cervical Cancer
Cervical cancer is the most serious HPV-associated cancer in women. Almost all cases of cervical cancer are caused by infection with high-risk HPV. Around 13,170 new cervical cancer cases are diagnosed yearly in the U.S., resulting in 4,250 deaths. Routine Pap smear screening has helped significantly reduce cervical cancer incidence and mortality.
Abnormal cell changes on the cervix (cervical dysplasia) can be detected through Pap smears before developing into cervical cancer. Most cases of mild dysplasia resolve without treatment as the immune system clears the HPV infection. However, more severe dysplasia may require excisional procedures to remove the affected tissue.
Other Cancers
While cervical cancer is the most prevalent, other cancers are also associated with high-risk HPV strains:
- Oropharyngeal cancers – Cancers of the tonsils, tongue base, soft palate, pharynx and other parts of the throat. HPV is linked to around 70% of these cancers in the U.S., or around 14,500 cases per year.
- Anal cancer – Around 91% of anal cancers (4,280 cases annually) are linked to HPV.
- Vulvar cancer – Around 75% of vulvar cancers (6,020 cases per year) are associated with HPV.
- Penile cancer – Around 63% of penile cancers (1,320 cases annually) are linked to HPV.
- Vaginal cancer – Around 78% of vaginal cancers (890 cases per year) are caused by HPV.
Rates of HPV-positive oropharyngeal cancers are increasing, likely due to changing sexual behaviors that have increased oral HPV exposure. HPV vaccination can help prevent infection and reduce these cancers in the future.
Testing for HPV
There are two main tests available for HPV:
1. HPV DNA Test
This test detects the genetic material (DNA) of high-risk HPV strains in a sample taken from the cervix or vagina. A positive HPV DNA test means you have a current HPV infection. It can identify women at increased risk of cell abnormalities on the cervix (precancerous changes) who may need more frequent screening.
The HPV DNA test is usually used together with a Pap smear (called co-testing). A negative HPV DNA test is also important, as it means any abnormal Pap results are not related to high-risk HPV and are likely to resolve on their own without treatment.
2. HPV Antibody Test
Unlike the DNA test, this blood test detects antibodies produced by the immune system in response to a previous HPV infection. It can determine if you have been exposed to HPV strains 16, 18 or others, but cannot tell if you have a current HPV infection. This test is not used for routine screening.
A positive antibody test means you were infected with HPV at some time. However, many sexually active adults will have a positive antibody test, so the results must be considered along with your other risk factors. The test can be useful when discussing HPV protection with partners.
Is HPV Treatment Necessary?
There is currently no medication or treatment that will get rid of HPV once infected. However, the immune system clears most infections naturally within 1-2 years. Since HPV often causes no symptoms, simply monitoring the infection is sometimes the best approach.
However, any abnormal cell changes caused by HPV do require treatment. This may include:
- Cryotherapy – Using extreme cold to destroy abnormal tissue.
- LEEP – Loop electrosurgical excision procedure that uses a thin wire loop with electrical current to remove abnormal cells.
- Cone biopsy – Surgery to remove a cone-shaped piece of tissue from the cervix.
Regular Pap testing allows early detection and treatment of any cell abnormalities before they possibly progress to cervical cancer. With early intervention, development of cervical cancer is very unlikely.
Preventing HPV Infection
There are steps you can take to avoid getting infected with HPV:
- Get vaccinated – HPV vaccines provide effective prevention against infection from high-risk strains most likely to cause cancers and genital warts.
- Use condoms – Condoms reduce HPV transmission, though they do not eliminate risk fully.
- Limit sexual partners – Having fewer partners lowers your odds of getting infected.
- Don’t smoke – Smoking weakens the immune system’s ability to clear HPV infections.
- Get screened – Women should have regular Pap tests to allow early treatment of any cervical cell changes before they develop into cancer.
HPV Vaccination
Safe and effective vaccines are available that protect against HPV infection from the cancer-causing strains. The CDC recommends routine HPV vaccination for girls and boys starting at ages 11-12. The vaccine is approved for use up to age 45.
The HPV vaccine is given as a series of shots over 6-12 months. The vaccines protect against infection from HPV types 16 and 18, which cause 70% of cervical cancers. The vaccines also provide protection against other cancer-linked strains like 31, 33, 45, 52 and 58.
HPV vaccination works best when administered before any exposure to HPV through sexual contact, as the vaccine does not treat existing HPV infections. However, vaccination can still benefit young women under age 26 and young men under 21, even if they have been exposed to HPV.
Conclusion
Most HPV infections will resolve on their own without causing health problems. However, some high-risk strains can lead to cancer over time if not treated. Cervical cancer is the most common HPV-related cancer in women. Other cancers linked to HPV include oropharyngeal, anal, vulvar, vaginal and penile cancers.
There is no cure for HPV once infected, but any abnormal cell changes can be detected through Pap smears and treated early to prevent progression to cervical cancer. HPV vaccines provide strong protection against the strains most likely to cause cancer. Using condoms, limiting sexual partners, not smoking and getting screened can also reduce your cancer risk.
While concerning, most cases of HPV do not become cancerous. With proper screening and vaccination efforts, the risks associated with HPV can be well managed.
| HPV Strain | Cancer Risk |
|---|---|
| HPV 16 and 18 | High – Cause 70% of cervical cancers |
| HPV 31, 33, 45, 52, 58 | Moderate – Cause 20% of cervical cancers |
| HPV 6, 11 | Low – Genital warts |
Key Points
- Over 100 HPV strains exist. Around 40 can be sexually transmitted.
- High-risk HPV can cause cancers of the cervix, anus, mouth/throat, penis, vulva, vagina.
- HPV 16 and 18 cause 70% of cervical cancers.
- Most people clear HPV within 1-2 years without health effects.
- Pap tests detect cervical cell changes for early treatment before cancer develops.
- HPV vaccines help prevent infection from high-risk cancer-causing strains.