The human papillomavirus, or HPV, is the most common sexually transmitted infection in the United States. According to the Centers for Disease Control and Prevention (CDC), about 43 million Americans had a sexually transmitted form of HPV in 2018, the latest year for which statistics are available, and 13 million become newly infected that year.

For most people infected with HPV, the virus doesn’t cause any health problems, but for some, it leads to genital warts or cancer. Of particular concern is the growing rate of oropharyngeal (mouth and throat) cancer caused by HPV, as reported in an investigation published December 16, 2021, in JAMA Otolaryngology Head and Neck Surgery. But HPV plays a significant role in multiple kinds of cancer, including cervical cancer and anal cancer.

In many cases, HPV infection is vaccine-preventable, but as of 2020, less than 60 percent of adolescents in the United States were fully vaccinated against HPV, according to an article published September 3, 2021, in the CDC's Morbidity and Mortality Weekly Report.

Experts worry that many people are still fuzzy on details about the virus — including how it’s transmitted, who is most at risk, and how to protect yourself from infection.

“There’s so much that people don’t know or misunderstand about HPV,” says William Robinson, MD, a gynecologic oncologist at the University of Mississippi Medical Center in Jackson. Here’s what leading experts say about some aspects of HPV that may surprise you.

1. Odds Are You’ve Probably Had HPV

“If you’ve been sexually active, you’ve got at least a 50 percent chance of having had the virus,” says Dr. Robinson. But not all forms of HPV carry the same health risks.

HPV is actually an umbrella term for more than 150 strains of related viruses, most of which are relatively harmless. About 40 of them can infect the genital areas, and a smaller number can cause genital warts or cancer.

Most of the time, you’ll never even know you’ve had HPV, because most strains (except those that cause warts) don’t cause any symptoms. And in about 90 percent of cases, the immune system clears the virus naturally within two years, according to the CDC. But when HPV does not go away on its own, some HPV strains can cause a variety of types of cancer.

People who have HIV are more likely to have HPV infections that persist, raising their chances of developing an HPV-related cancer.

2. Condoms Can’t Completely Protect You From HPV

While using condoms can reduce your risk of HPV infection, it can’t eliminate this risk entirely.

“The virus can live in the scrotum and the hair-bearing areas of the genitals,” says Barbara Goff, MD, a gynecologic oncologist and surgeon-in-chief at the University of Washington Medical Center in Seattle. This means that any skin-to-skin genital contact can transmit the virus, as can oral, vaginal, and anal sex.

“That’s why it’s so important for young people to get vaccinated for HPV well before they become sexually active,” says Dr. Goff.

3. If You Have HPV, Your Current Partner May Not Be to Blame

If you learn that you have HPV — which is most likely to occur after a cervical HPV test or Pap smear — don’t jump to conclusions about how you got the infection.

“Some patients assume that their current sexual partner gave it to them,” says Robinson. “But that’s probably not the case. The women who develop cervical cancer at age 40 probably got infected shortly after [having sex] with their first sexual partner.”

That’s because HPV can stay dormant for years before it starts causing the cell damage that can lead to cancer. HPV-triggered cancers can take years, or even decades, to develop.

4. Cervical Cancer Isn’t the Only Cancer Caused by HPV

Most people who know about HPV associate it with cervical cancer, but the virus is increasingly implicated in other forms of cancer — including oropharyngeal cancers, as well as cancers of the vulva, vagina, anus, and penis. Evidence suggests that women who have had cervical cancer or precancerous changes (known as dysplasia) in the cervix are at greater risk for HPV-related cancers in other areas of the body, according to Goff.

The CDC estimates, based on data from 2014 to 2018, that each year in the United States:

25,719 women and 20,424 men develop some form of HPV-associated cancer
20,236 men and women develop oropharyngeal (mouth and throat) cancer
12,200 women develop cervical cancer
7,288 women and men develop anal cancer
4,191 women develop vulvar cancer
1,365 men develop penile cancer
863 women develop vaginal cancer

Not all cases of cancer in these areas of the body are caused by HPV, but the majority are. The CDC estimates that 91 percent of cervical cancer cases are caused by HPV, as are 91 percent of anal cancer cases, as well as 69 percent of vulvar cancers and 63 percent of penile cancer cases.

There are currently no established screening guidelines for HPV-related cancers other than cervical cancer. But researchers are exploring how to identify people at high risk for other HPV-associated cancers, so that these cancer cases can be identified and treated early.

For people at risk for anal cancer, anal cytology testing (also called the anal Pap test) can be used to check for abnormal cells in the anal canal. Some medical societies recommend this test for sexually active adults with HIV starting around ages 25 to 30, but anyone with a suppressed immune system — such as organ transplant recipients — may be at higher risk for anal cancer. You don’t need to have receptive anal sex to be at higher risk for anal cancer, since HPV can make its way into the anal canal from nearby areas.

5. Smoking Raises Your Risk for HPV-Related Cancer

“Smoking weakens the immune system, which can allow HPV to grow more rampantly,” says Sharyn Lewin, MD, the medical director of gynecologic oncology at Holy Name Medical Center in Teaneck, New Jersey. If you want to prevent a dormant HPV infection from turning into a precancerous or cancerous growth, kick your cigarette habit today.

6. The HPV Vaccine Isn’t Just for Girls

The HPV vaccine not only provides women with nearly 100 percent protection against cervical cancer caused by HPV types 16 and 18 — which cause 70 percent of cervical cancer cases — but it also provides direct health benefits for men, including prevention of genital warts. And although conclusive studies have yet to be done, many researchers believe that vaccination of boys will eventually reduce rates of oropharyngeal and other cancers as well.

Gardasil 9, the HPV vaccine currently available in the United States, is approved by the U.S. Food and Drug Administration (FDA) for use in all people ages 9 to 45.

The CDC recommends HPV vaccination for all preteens at age 11 or 12, or starting at age 9 if desired.
Vaccination is also recommended for all people up to age 26 if they haven’t already been vaccinated.
For adults ages 27 to 45, the CDC recommends discussing your risk for new HPV infections and the potential benefits of vaccination with your healthcare provider.

7. You Still Need Cervical Screening Even If You’ve Gotten the HPV Vaccine

The HPV vaccine doesn’t protect against all potentially high-risk types of HPV, nor does it protect against any strains of the virus a person was exposed to before vaccination. So periodic cervical HPV tests or Pap tests are still recommended for women who have had the HPV vaccine.

Gardasil 9, the HPV vaccine, protects against HPV types 16, 18, 31, 33, 45, 52, and 58, all of which can cause cancer, as well as types 6 and 11, which can cause genital warts. Two earlier HPV vaccines, Cervarix and Gardasil, protect against fewer HPV strains.

8. The HPV Vaccine Doesn't Treat HPV

This may seem obvious, but it bears repeating: The HPV vaccine is only preventive. It doesn’t fight the virus in people who already have it. That’s partly why it’s recommended primarily for children and young adults — chances are that if you’re older, you’ve already been exposed to at least some of the HPV strains the vaccine protects against. But this isn’t always the case, of course, which is why Gardasil 9 is approved for adults up to age 45.

There’s no treatment for HPV infection, although it can go away on its own. Women who have abnormal HPV or Pap test results may be advised to have additional tests to further examine any abnormality, to undergo treatment to remove the abnormal cells, or to wait and get retested in three to six months, according to the American College of Obstetricians and Gynecologists.

Additional reporting by Quinn Phillips.

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