HPV, or human papillomavirus, is a group of more than 200 related viruses that infect skin and mucous membranes. Most strains do nothing you’d ever notice. Your immune system clears about 90% of infections within two years without any symptoms at all. But certain strains can cause genital warts, and a smaller subset can, over many years, lead to cancer. Almost all sexually active people will contract HPV at some point in their lives, making it the most common sexually transmitted infection worldwide.
How HPV Gets Into Your Body
HPV needs a way past your outer layer of skin to reach the cells it targets. It enters through tiny breaks or micro-abrasions in the skin or mucous membranes, the kind that occur naturally during sexual contact, minor friction, or small wounds. The virus doesn’t initially latch onto skin cells themselves. Instead, it binds to proteins on the exposed basement membrane, the structural layer just beneath the surface. This binding triggers a shape change in the virus that allows it to attach to the basal cells migrating in to heal the wound.
Once bound, the virus is remarkably slow. It takes 2 to 4 hours just to get inside a cell, and another 20 or so hours before it reaches the cell’s nucleus and starts producing its genetic instructions. From there, HPV essentially hitches a ride on your body’s natural skin renewal process. As basal cells divide and push upward toward the surface, the virus replicates along with them. It stays quiet in the lower layers and ramps up production of new viral particles only as cells reach the surface and are shed, which is how the virus spreads to new hosts without triggering a strong immune alarm.
Low-Risk vs. High-Risk Strains
Not all HPV strains behave the same way. Scientists divide them into two broad categories based on what they do in the body.
Low-risk strains, especially types 6 and 11, cause about 90% of genital warts. These warts are flat, raised, or stalk-like growths that appear on or around the genitals, anus, or surrounding skin. Common locations include the vaginal opening, the shaft of the penis, the foreskin, the perineum, and perianal skin. Warts can take months or even years to appear after initial infection, and while they can be uncomfortable or cosmetically bothersome, they don’t turn into cancer.
High-risk strains are a different story. There are 12 identified high-risk types: HPV 16, 18, 31, 33, 35, 39, 45, 51, 52, 56, 58, and 59. These strains rarely produce visible symptoms. Instead, they work silently inside cells, and in a small percentage of people whose infections persist, they can cause cellular changes that progress toward cancer.
How HPV Causes Cancer
Your cells have built-in brakes that prevent them from growing out of control. Two of the most important are tumor suppressor proteins called p53 and pRb. High-risk HPV strains produce two proteins that specifically disable these brakes.
The first viral protein hijacks a cellular recycling system to tag p53 for destruction. Without p53, damaged cells that would normally self-destruct instead survive and keep dividing. The second viral protein breaks apart the complex that keeps pRb functioning, releasing a signal that pushes cells into overdrive, forcing them to replicate far more aggressively than normal. With both brakes disabled simultaneously, cells accumulate genetic damage without any mechanism to stop, repair, or die. Over years, this can produce precancerous lesions and eventually invasive cancer.
This process is slow. The median HPV infection lasts about 11.5 months before the immune system clears it. At 24 months, 77% of infections have resolved. By 48 months, 89% are gone. Cancer only develops from infections that persist for years and are never cleared. Among women with infections lasting at least 6 months, roughly 7% developed moderate or severe precancerous cervical changes within 4 years. The progression from persistent infection to actual cancer typically takes a decade or longer.
Which Cancers HPV Causes
Cervical cancer is the most well-known consequence, but HPV causes cancer at several sites in the body. These include cancers of the vulva, vagina, penis, anus, and the oropharynx (the back of the throat, including the base of the tongue and tonsils). Most cancers of the vagina and the oropharynx contain HPV. HPV 16 alone is responsible for the majority of HPV-related cancers across all of these sites.
Oropharyngeal cancer linked to HPV has been rising sharply in recent decades, particularly among men. Unlike cervical cancer, there is no routine screening test for throat or anal HPV infections, which means these cancers are typically caught based on symptoms rather than early detection.
How Most Infections Resolve on Their Own
The immune system clears HPV without treatment in the vast majority of cases. At 12 months, 66% of infections are undetectable. By 24 months, that number reaches 90%. People with healthy immune function are especially likely to clear the virus completely, often without ever knowing they were infected.
What determines whether an infection clears or persists isn’t fully understood, but immune suppression (from HIV, organ transplant medications, or other causes) significantly raises the risk of persistence. Smoking also appears to impair the local immune response in cervical tissue, making clearance slower. When the immune system does succeed, it eliminates detectable virus, though whether small amounts of dormant HPV DNA remain in cells long-term is still debated.
Screening and Detection
There is no blood test for HPV. For cervical cancer screening, two main tools exist: the Pap smear (which looks for abnormal cells) and the HPV DNA test (which checks for the presence of high-risk strains directly).
Current U.S. guidelines recommend that women aged 21 to 29 get a Pap smear every 3 years. Starting at age 30, you have three options: a Pap smear every 3 years, an HPV test alone every 5 years, or both tests together every 5 years. The 5-year interval for HPV testing reflects the slow pace at which HPV-related changes develop, meaning less frequent screening still catches problems early.
There is no approved HPV screening test for men, and no routine screening exists for HPV-related cancers of the throat, anus, or penis in the general population.
How Vaccination Changes the Picture
The HPV vaccine protects against nine strains: the seven high-risk types responsible for most HPV cancers (16, 18, 31, 33, 45, 52, and 58) and the two low-risk types behind most genital warts (6 and 11). It is most effective when given before any exposure to the virus, which is why it’s recommended for preteens, though it’s approved for people up to age 45.
The real-world results have been dramatic. Within 12 years of the vaccine’s introduction in the U.S., infections with the targeted HPV types dropped 88% among females aged 14 to 19 and 81% among those aged 20 to 24. Cervical precancer rates among screened 18- to 20-year-olds fell by 50% compared to pre-vaccine levels. The vaccine can prevent more than 90% of HPV-related cancers when given at the recommended ages.