One of the most confusing sexually transmitted diseases (STDs) out there is human papillomavirus, or HPV. Despite the fact that it’s the most common STD in the United States, most Americans don’t know very much about it. So, whenever I wade into conversations about HPV on Internet message boards, I prepare myself to enter an ocean of misinformation and misunderstandings.

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The strains of HPV that cause genital warts are different from those that cause cancer.

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This post, in fact, was inspired by some particularly egregious falsehoods spouted by quite confident-sounding message-board denizens who were dispensing advice to a distraught man with genital warts. He had read that the virus responsible for genital warts was also responsible for cervical cancer, and was upset that he might have “given” cancer to his beloved girlfriend. While some commenters gave good advice, others shared ideas that were not factually correct — and in a forum devoid of sources or citations, it would have been difficult for him to distinguish the bad information from the good.

Situations such as these highlight why it’s not a great idea to get medical advice from the “hive mind” of the World Wide Web. I know American health-care access still isn’t all it can be, but dang — I hope most people know to use reputable sources, like the Centers for Disease Control and Prevention (CDC), whenever they take to the ’net in search of health information.

The first thing to know about HPV is that it can be spread by any type of sexual contact — penetrative and non-penetrative. It can be transmitted by vaginal sex and anal sex, as well as by oral sex or rubbing genitals together, even without penetration.

The second thing to understand about HPV infection is that it’s caused by a virus. There are 150 strains of this virus, numbered in the order of their discovery, such as HPV-6 or HPV-18. Most HPV strains cause warts on the hands or feet and are not transmitted sexually. But some strains of HPV can infect the genital, anal, and oral regions, and they are transmitted sexually. Of the sexually transmitted strains of HPV, some can cause warts, while others can cause cancer.

Let’s talk about warts that aren’t transmitted sexually. These are the warts that might appear on your face, hands, or feet. These strains of HPV, called cutaneous HPV, don’t consider the genital, anal, or oral regions to be part of their habitat, and they won’t set up camp there. So, if you have a wart on your finger, you cannot transfer the virus that caused it to your or your partner’s genital region.

Now let’s talk about warts that are transmitted by sexual contact. The sexually transmitted strains of HPV, called mucosal HPV, consider their habitat to be in the mucous membranes that make up your genital, anal, and oral regions. There are more than 40 sexually transmitted strains of HPV, and these viruses fall into one of two categories: “low risk” and “high risk.” Most sexually transmitted strains of HPV are low risk, but at least 13 high-risk strains of HPV have been identified.

A low-risk HPV strain can cause warts in the genital, anal, and oral regions. Most people who are infected with low-risk HPV don’t actually develop warts, but if they do, the warts usually go away once the immune system has defeated the infection, which can take up to two years. Only rarely do these infections persist, in which case someone could possibly see recurring genital warts throughout his or her life.

A high-risk HPV strain can lead to cancers of the cervix, throat, anus, vulva, vagina, or penis. These viral strains are genetically different from the low-risk strains, and are able to interfere with your cell cycle, which can possibly lead to cancer — a process that usually takes a decade or more.

Nine out of 10 people who are infected with a high-risk HPV strain are able to clear the virus in one to two years, meaning that their immune system defeats it. However, some people develop persistent infections, and in a percentage of those cases, these infections can develop into precancerous lesions — which can be caught and treated, for example by a Pap test. Untreated, up to half of these precancerous lesions will progress into cancer. But the majority of people infected with high-risk HPV do not develop cancer as a result — which is good news, given that an estimated 79 million Americans are currently infected with HPV, and that pretty much every sexually active person is expected to get it at least once.

Some people are confused by this terminology, thinking that a “low-risk” HPV strain isn’t as likely to cause cancer as a “high-risk” strain, but still could. That is incorrect. A wart-causing HPV strain is called “low risk” simply because warts pose less risk to one’s health than cancer. Of course, it’s possible to be simultaneously infected with more than one HPV strain. Just because you have genital warts doesn’t mean you’re not also infected with a high-risk HPV strain. But you also don’t need to worry about “giving” your partner cancer as if it’s some foregone conclusion.

Vaccination is the best way for sexually active people to be protected from HPV. Gardasil immunizes against the HPV strains responsible for most genital warts and HPV-associated cancers. The newest version, Gardasil 9, protects recipients from seven high-risk HPV strains that cause 90 percent of cervical and anal cancers, as well as two low-risk HPV strains that together cause 90 percent of genital warts. The reason vaccination is so great is because, while condoms offer some protection against HPV, they’re limited by the amount of skin they cover — and HPV is transmitted by skin-to-skin contact. There is also no test to tell you what your HPV status is, so vaccination can give you some peace of mind.

Planned Parenthood health centers offer Gardasil. Learn more from Planned Parenthood and the CDC.

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