HPV, or human papillomavirus, is the most common sexually transmitted infection in the United States. More than 42 million Americans currently carry strains known to cause disease, and roughly 13 million new infections occur every year. Most people who get HPV never develop symptoms, and their immune systems clear the virus without treatment. But certain strains can cause genital warts, and others can lead to cancer years or even decades after the initial infection.
How HPV Spreads
HPV is a DNA virus that infects skin and mucous membrane cells. It spreads through skin-to-skin contact, most commonly during vaginal, anal, or oral sex. Condoms reduce the risk but don’t eliminate it, because the virus can infect areas a condom doesn’t cover. You can carry and transmit HPV without knowing it, since the infection rarely produces visible signs. Symptoms can also appear years after sexual contact with an infected person, making it nearly impossible to trace when or from whom you picked it up.
Low-Risk vs. High-Risk Strains
There are more than 200 types of HPV, but only a few dozen affect the genital area, and they fall into two broad categories.
Low-risk strains, especially types 6 and 11, cause genital warts. These account for more than 90% of wart cases. Warts typically appear as small bumps in the genital or anal area. They can be flat or raised, appear alone or in clusters, and sometimes have a cauliflower-like texture. They’re not dangerous, but they can be uncomfortable and distressing. Warts may go away on their own, stay the same, or grow in size or number.
High-risk strains are the ones that can cause cancer. Types 16 and 18 are the most significant: together they’re responsible for about 66% of cervical cancers worldwide. Five additional high-risk types (31, 33, 45, 52, and 58) account for another 15% of cervical cancers. FDA-approved HPV tests screen for up to 14 high-risk strains. These strains don’t cause warts. Instead, they quietly infect cells and, if the infection persists, can trigger changes that eventually become cancerous.
Cancers Linked to HPV
HPV doesn’t only cause cervical cancer. It’s connected to cancers across several body sites, and the percentages are striking:
- Cervical cancer: 91% of cases are caused by HPV
- Anal cancer: 91% (93% in women, 89% in men)
- Vaginal cancer: 75%
- Oropharyngeal cancer (back of the throat, base of the tongue, tonsils): 70% (72% in men, 63% in women)
- Vulvar cancer: 69%
- Penile cancer: 63%
Oropharyngeal cancer linked to HPV has been rising sharply in men over the past two decades. This is now one of the most common HPV-related cancers in the United States, a fact that surprises many people who associate HPV primarily with cervical cancer.
Why Most Infections Never Cause Problems
About 90% of HPV infections clear on their own within 6 to 18 months. Your immune system recognizes the virus and eliminates it before it causes lasting cell changes. During this time you likely won’t know you’re infected.
The remaining infections can persist, and that persistence is the real risk factor. When a high-risk strain lingers for years, it can gradually alter the DNA of infected cells, pushing them toward precancerous changes and, eventually, cancer. This process is slow. Cervical cancer, for example, typically takes 10 to 20 years to develop from an initial infection, which is why regular screening catches problems early in most cases. People with weakened immune systems are more likely to experience persistent infections and faster progression.
Screening and Early Detection
Cervical cancer screening is the primary tool for catching HPV-related disease before it becomes dangerous. The preferred approach is an HPV test, which checks cervical cells for the presence of high-risk strains. This can be done alone (primary HPV testing) or combined with a Pap test, which looks for abnormal cell changes under a microscope.
Current guidelines from the American Cancer Society recommend that people with a cervix and average cancer risk can stop screening after age 60 to 65 if they’ve had consistently negative HPV tests. If only Pap tests are available, three consecutive negative results at recommended intervals, with the last at age 65, are considered acceptable.
There is no approved screening test for HPV-related cancers of the throat, anus, or penis in the general population. These cancers are typically found when symptoms appear, such as persistent sore throat, difficulty swallowing, unexplained bleeding, or lumps that don’t go away.
The HPV Vaccine
Vaccination is the most effective way to prevent HPV infection. The current vaccine protects against nine HPV types, including the two that cause most cancers (16 and 18) and the two that cause most genital warts (6 and 11).
The CDC recommends routine vaccination at ages 11 or 12, though the series can start as early as age 9. Children who begin the series before their 15th birthday need only two doses, spaced 6 to 12 months apart. Those who start at 15 or older need three doses, given over about six months. The vaccine is recommended through age 26 for anyone who wasn’t fully vaccinated earlier, and it’s available up to age 45 for adults who discuss the decision with their healthcare provider.
The vaccine works best before any exposure to the virus, which is why it’s recommended well before most people become sexually active. But even people who’ve already been infected with one strain benefit from protection against the others. The vaccine does not treat existing infections or cell changes that have already occurred.
Treatment for HPV-Related Conditions
There is no antiviral medication that cures HPV itself. Treatment targets the problems the virus causes, not the virus directly.
Genital warts can be treated with prescription creams applied at home or removed in a clinic through freezing, burning, or minor surgical procedures. Warts sometimes recur even after treatment, because the underlying virus may still be present in nearby skin cells. Many people find that recurrences become less frequent over time as their immune system gains better control of the infection.
Precancerous cell changes found during screening are treated with procedures that remove or destroy the abnormal tissue. These are typically outpatient procedures with short recovery times. When caught at the precancerous stage, treatment is highly effective at preventing cancer from developing. HPV-related cancers that are diagnosed early also tend to respond well to treatment, which is why screening matters so much for the cancers where screening exists.