Human papillomavirus, or HPV, is the most common sexually transmitted infection in the United States. Around 79 million Americans currently have it, and roughly 80% of women will contract at least one type during their lifetime. Most people who get HPV never develop symptoms, and in many cases the immune system clears the virus on its own. But certain strains can cause genital warts, and others can lead to cancer years or even decades after the initial infection.
How HPV Infects the Body
HPV is a family of small, double-stranded DNA viruses that specifically target epithelial cells, the thin layer of tissue covering your skin and lining your mucous membranes. The virus enters through tiny breaks or micro-abrasions in that surface layer and lodges in the basal cells underneath, where new skin cells are produced. Once inside, it hijacks the cell’s machinery to make copies of itself as those cells divide and move toward the surface.
This is why HPV thrives in areas where skin-to-skin contact is common during sex: the genital area, the anus, the mouth, and the throat. The virus doesn’t travel through the bloodstream like HIV or hepatitis. It stays in the epithelial tissue, which also explains why condoms reduce but don’t eliminate the risk, since they don’t cover all the skin that can carry the virus.
How HPV Spreads
HPV spreads most commonly during vaginal or anal sex, but it can also be transmitted through oral sex and close skin-to-skin touching during sexual contact. A person can pass the virus to a partner even when they have no visible warts or any other signs of infection. This makes HPV particularly easy to transmit without either partner knowing. There’s no way to determine exactly when or from whom you contracted the virus, since it can remain dormant for months or years before anything shows up on a test or on your body.
Not All Strains Are Equal
There are over 200 types of HPV, but only a fraction cause serious health problems. Scientists divide the sexually transmitted types into two broad categories: low-risk and high-risk.
The low-risk types, especially HPV 6 and HPV 11, are responsible for about 90% of genital warts. These warts are usually painless, flat or slightly raised growths that appear on or around the genitals and anus. They can show up as a single bump or in clusters, and while they’re often more of a cosmetic and emotional concern than a medical one, they can occasionally be uncomfortable depending on their size and location. Low-risk HPV types don’t cause cancer.
The high-risk types are a different story. There are 12 of them: HPV 16, 18, 31, 33, 35, 39, 45, 51, 52, 56, 58, and 59. These strains can cause cells to change in ways that, over time, lead to cancer. HPV 16 and 18 are the most dangerous of the group, responsible for the majority of HPV-related cancers. A high-risk HPV infection produces no symptoms on its own. You won’t feel it, and the only way to detect it is through screening.
Cancers Linked to HPV
More than 9 out of every 10 cervical cancers are caused by HPV, making it the most well-known consequence of the virus. But cervical cancer is far from the only one. Based on U.S. cancer registry data from 2018 to 2022, HPV causes an estimated 16,000 cases of throat cancer (specifically oropharyngeal cancer) each year, making it the most common HPV-related cancer in terms of raw numbers. It also accounts for roughly 7,600 anal cancers, 3,000 vulvar cancers, 900 penile cancers, and 700 vaginal cancers annually.
Cancer doesn’t develop quickly after infection. It typically takes years, often decades, for a persistent high-risk HPV infection to progress through precancerous cell changes and eventually become cancer. Most people’s immune systems clear even high-risk HPV before it ever reaches that point. The danger comes when the virus persists in the same cells for a long time, gradually accumulating the kind of damage that turns normal tissue into cancerous tissue.
How HPV Is Detected
For people with a cervix, screening is the primary tool for catching HPV-related problems early. There are three main approaches: an HPV test that checks cells for high-risk strains, a Pap test that looks for abnormal cell changes, and a combination of both (called a cotest).
The American Cancer Society recommends starting cervical cancer screening at age 25 with an HPV test every five years through age 65. The U.S. Preventive Services Task Force starts screening at age 30 for HPV testing alone (every five years) or a cotest (every five years), while allowing Pap tests every three years starting at age 21. Either set of guidelines catches precancerous changes early enough to treat them before they progress.
There is currently no approved screening test for HPV-related cancers of the throat, anus, or penis. For these sites, detection relies on noticing symptoms like persistent sores, lumps, or difficulty swallowing and getting evaluated. This gap is one reason the vaccine is so important for prevention.
The HPV Vaccine
The current HPV vaccine, Gardasil 9, protects against nine HPV types: the seven high-risk strains responsible for most HPV-related cancers (types 16, 18, 31, 33, 45, 52, and 58) and the two low-risk types that cause most genital warts (types 6 and 11).
The CDC recommends two doses at ages 11 to 12, given 6 to 12 months apart. Vaccination can start as early as age 9. If you get your first dose before your 15th birthday, two doses are all you need. People who start the series between ages 15 and 26 need three doses spread over six months. The same three-dose schedule applies to anyone with a weakened immune system between ages 9 and 26.
The vaccine works best when given before any exposure to the virus, which is why it’s recommended before most people become sexually active. But even if you’ve already been exposed to one or two HPV types, the vaccine still protects against the remaining types it covers. It does not treat existing infections or clear an HPV strain you’ve already contracted.
What Happens After a Diagnosis
If you test positive for HPV, the most important thing to understand is that most infections resolve on their own. Your immune system will typically suppress or clear the virus within one to two years. A positive HPV test doesn’t mean you have cancer or will develop it. It means your screening is working and your doctor can monitor for any cell changes over time.
If your screening shows abnormal cell changes, your doctor may recommend more frequent monitoring or a procedure to examine the cervix more closely. Precancerous changes caught at this stage are highly treatable, which is exactly why regular screening matters.
For genital warts, several treatment options can remove the visible growths, though the underlying virus may still be present and warts can recur. Treating warts doesn’t eliminate the infection itself, and the virus can still be transmitted to partners even after warts are removed.
Because HPV spreads through skin contact and can be transmitted without any visible signs, there’s no guaranteed way to prevent passing it to a sexual partner other than abstaining from contact. Condoms lower the risk but don’t eliminate it entirely. There’s no blood test for HPV and no approved test for the virus in men, which means many people carry and transmit it without ever knowing.