HPV (human papillomavirus) can cause genital warts, six types of cancer, and a rare condition involving growths in the airway. Most HPV infections clear on their own without ever causing problems, but certain strains carry serious long-term risks. What happens depends largely on which type of HPV you’re infected with.
High-Risk vs. Low-Risk Strains
There are over 100 strains of HPV, but they fall into two broad categories: low-risk and high-risk. Low-risk strains, primarily types 6 and 11, cause non-cancerous conditions like genital warts and growths in the respiratory tract. They don’t lead to cancer.
High-risk strains are a different story. Types 16 and 18 are the most dangerous, together 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 and 11% of all HPV-related cancers. High-risk HPV is detected in 99% of cervical precancers.
Genital Warts
Genital warts are the most visible and common non-cancerous consequence of HPV. Over 90% of cases are caused by low-risk HPV types 6 or 11. The warts appear as flesh-colored bumps in the genital or anal area and can be flat, raised, or cauliflower-shaped. They’re not dangerous in themselves, but they can be uncomfortable and tend to recur. Treatments range from topical medications to procedures that remove the warts, though none eliminate the underlying virus.
Cervical Cancer
Cervical cancer is the condition most closely tied to HPV. The progression from initial infection to cancer is slow. It typically takes 15 to 20 years for abnormal cervical cells to become cancerous, giving screening programs a wide window to catch changes early. In people with weakened immune systems, such as those with untreated HIV, that timeline can compress to 5 to 10 years.
The way high-risk HPV causes cancer comes down to two viral proteins that hijack the cell’s normal safety mechanisms. One protein targets and destroys a key molecule (p53) that normally tells damaged cells to stop dividing or die. The other disables a separate molecule (pRb) that acts as a brake on cell growth. With both of these protective systems knocked out, infected cells accumulate genetic damage and keep dividing unchecked. Over years, this can progress from precancerous changes to invasive cancer.
Because the timeline is long and detectable precancers precede actual cancer, screening is highly effective. Current guidelines from the U.S. Preventive Services Task Force recommend that people aged 30 to 65 get an HPV test every 5 years, an HPV/Pap cotest every 5 years, or a Pap test every 3 years. The American Cancer Society recommends starting HPV testing at age 25 and repeating every 5 years through age 65.
Oropharyngeal Cancer
HPV-related throat cancer, specifically cancer of the oropharynx (the back of the throat, base of the tongue, and tonsils), has been rising sharply and is now more common than cervical cancer in the United States. About 22,585 oropharyngeal cancers are diagnosed annually, and roughly 70% of them, around 16,000 cases, are attributable to HPV. Men are disproportionately affected: 72% of oropharyngeal cancers in men are HPV-related, compared to 63% in women. In raw numbers, that’s about 13,600 cases in men versus 2,400 in women each year.
Unlike cervical cancer, there’s currently no routine screening test for HPV-related throat cancer. Symptoms often include a persistent sore throat, difficulty swallowing, ear pain on one side, or a lump in the neck. The good news is that HPV-positive oropharyngeal cancers tend to respond better to treatment and have higher survival rates than those caused by tobacco and alcohol.
Anal, Penile, Vulvar, and Vaginal Cancers
Beyond the cervix and throat, high-risk HPV causes cancers of the anus, penis, vulva, and vagina. These are less common individually, but collectively they add thousands of cases each year. Anal cancer has a particularly strong HPV connection. People at higher risk include those with HIV, men who have sex with men, and anyone with a history of persistent HPV infection in the anal area.
Vulvar and vaginal cancers affect a smaller number of people but follow the same pattern: high-risk HPV strains drive precancerous changes that can progress over years. Penile cancer is rare overall, but HPV is a significant contributor in the cases that do occur.
Recurrent Respiratory Papillomatosis
One of the lesser-known consequences of HPV is recurrent respiratory papillomatosis (RRP), a condition where non-cancerous growths called papillomas develop in the airway, most often on or near the vocal cords. HPV types 6 and 11, the same low-risk strains behind genital warts, are the usual cause. HPV 11 tends to produce more aggressive growths.
RRP can appear in children or adults. Children typically acquire the virus from their mother during vaginal delivery if she has active genital warts, though transmission has also been documented during cesarean delivery, suggesting the fetus can be exposed before birth. Adults with RRP may have been exposed to HPV at birth, with the virus lying dormant in healthy cells for years before something triggers it.
Symptoms include a persistently raspy voice, noisy or high-pitched breathing, chronic cough, difficulty swallowing, and snoring. In children, the condition can affect growth and cause recurrent pneumonia. The growths can be surgically removed, but they frequently come back, sometimes requiring dozens of procedures over a lifetime.
How Vaccination Reduces These Risks
The HPV vaccine (Gardasil 9, the only version currently used in the U.S.) protects against nine HPV types, including the two highest-risk cancer-causing strains and the two strains responsible for most genital warts and RRP. Early vaccination has resulted in a 40% reduction in cervical precancers and more than an 80% reduction in the overall risk of developing cervical cancer. Because the vaccine targets the strains behind the majority of HPV-related cancers across all affected body sites, these protective effects extend beyond the cervix to the throat, anus, vulva, vagina, and penis.
The vaccine works best when given before any exposure to HPV, which is why it’s recommended for preteens at age 11 or 12. It can be given as early as age 9 and is available through age 26 for anyone not previously vaccinated. Adults aged 27 to 45 can discuss catch-up vaccination with their healthcare provider, though the benefit decreases with age since prior exposure becomes more likely.