Although certain human papillomavirus (HPV) strains are linked to anal cancer, contracting one doesn’t necessarily mean you’ll go on to develop cancer.

“An overwhelming majority of anal cancers are caused by infection with human papillomavirus [HPV],” says Syed G. Husain, a colorectal surgeon at The Ohio State University Comprehensive Cancer Center.

According to the Centers for Disease Control and Prevention (CDC), about 7,531 people receive an anal cancer diagnosis each year.

Approximately 91% of anal cancer diagnoses are said to be caused by HPV. That means about 6,900 people per year develop HPV-related anal cancer.

Ahead, read more about the connection between HPV and anal cancer. Plus, learn how you can protect yourself from HPV more generally, as well as how to reduce your risk of anal cancer if you currently have HPV.

“The HPV virus can infect the anal cells,” explains Michelle Forcier, MD, a gender affirming clinician with the virtual healthcare service FOLX. “When this happens, the anal cells can mutate and some become cancerous.”

To be clear: Not everyone who has HPV will develop anal cancer.

“The vast majority of patients who get [develop] HPV will clear the virus naturally, and thus will not have the virus lead to or progress to cancer,” she explains.

People who have a compromised immune system may be less likely to clear the virus without treatment and may be more likely to develop complications as a result of an HPV infection.

Some research suggests that people who have HIV and develop HPV, for example, have a higher risk of developing HPV-related anal cancer than people who don’t have HIV.

It’s unclear what exactly causes the other 9% percent of anal cancer cases.

But there are a number of known factors that can increase your risk, explains Jennifer Chuy, MD, an oncologist at NYU Langone’s Perlmutter Cancer Center.

According to Chuy, you may be more likely to develop anal cancer if you:

There are certain strains of HPV that can increase your risk of developing anal cancer, and there are certain lifestyle choices that may also increase your risk.

But developing anal cancer is never the fault of any individual.

Making a few lifestyle changes may reduce your risk of developing anal cancer if you have HPV.

For starters, consider quitting smoking if you smoke, says Chuy. “Certainly, you shouldn’t start smoking or using other tobacco products if you don’t already,” she says.

You may also want to get the HPV vaccine if you’re still eligible. (Most people under the age of 45 are.)

“Even if you already have HPV, getting the HPV vaccination can still protect you from other strains that may cause harm,” says Chuy.

“Limiting the number of sexual partners and using barrier protection to prevent other sexually transmitted infections can also lower your risk,” she says.

You can also make it a point to be checked for anal cancer regularly.

“Routine anal cancer screenings via an anal Pap smear or high resolution anoscopy have been shown to reduce cancer risk in patients with HPV,” says Husain.

If you have questions about your STI status or are experiencing any unusual symptoms, consult with a healthcare professional.

This includes any of the following symptoms related to anal cancer:

A healthcare professional will be able to discuss your individual risk factors and advise you on what STI tests you need, if any.

People with vulvas and vaginas can get tested for HPV, but there isn’t a test for people with penises at this time.

No matter your anatomy, if you’re experiencing symptoms linked to anal cancer or have had receptive anal sex, a clinician may recommend an anal Pap test.

An anal Pap test allows your clinician to collect a tissue sample from inside of your anal canal. They’ll send this sample to a lab to check for abnormalities.

Depending on your set of symptoms, your clinician may also recommend a visual rectal exam, a digital rectal exam, or anal ultrasound.

What strains of HPV can cause or increase your risk of anal cancer?

HPV strains 16 and 18 are the strains most likely to increase your risk of cancer, says Chuy.

“Other strains, like 31, 33, 35, 39, 45, 51, 52, 56, 58, 59, 66, and 68, are also occasionally implicated in cancer formation,” she says.

Can HPV cause or increase your risk of other cancers?

Anal cancer isn’t the only cancer linked to HPV.

HPV may also increase your risk of cancers affecting the:

What causes HPV?

HPV is a sexually transmitted virus that, as of 2018, affects 43 million people. There are more than 100 different strains of the HPV virus.

Most people who have genital, oral, or anal sex will come in contact with one or more strains of the virus at some point, says Forcier.

But you can still take measures to reduce your risk of contracting the virus.

What can you do to reduce your risk of or prevent HPV?

Getting the HPV vaccine, using barriers during sexual activity, talking with potential partners about their STI status, and limiting your number of sexual partners can reduce your risk, says Forcier.

“The more partners an individual has, the more potential an individual has at being exposed to HPV,” she says.

It’s important to note that, while condoms and other barrier methods provide some protection, they aren’t 100% preventive.

“Currently, the best way to reduce your risk of getting HPV is by getting the HPV vaccine,” says Husain.

All HPV vaccines are effective at reducing the risk of HPV strains 16 and 18, which are the two strains most commonly linked to cancer.

What can you do to reduce your risk of or prevent anal cancer?

If you smoke, consider quitting. Also consider using a condom or other barrier method during sex, getting the HPV vaccine, and getting checked for anal cancer regularly if you have HPV.

There’s a connection between HPV strains 16 and 18 and anal cancer.

But not everyone who contracts these strains will develop anal cancer. Similarly, many people who have anal cancer don’t have HPV.

If you have questions about your STI status or your anal cancer risk, talk with a healthcare professional.

Gabrielle Kassel (she/her) is a queer sex educator and wellness journalist who is committed to helping people feel the best they can in their bodies. In addition to Healthline, her work has appeared in publications such as Shape, Cosmopolitan, Well+Good, Health, Self, Women’s Health, Greatist, and more! In her free time, Gabrielle can be found coaching CrossFit, reviewing pleasure products, hiking with her border collie, or recording episodes of the podcast she co-hosts called Bad In Bed. Follow her on Instagram @Gabriellekassel.