Human papilloma virus (HPV) is the virus that causes most cervical, vaginal, and anal cancers. It also causes cancer of the vulva, and penis. More recently, HPV has been identified as an increasing cause of head and neck cancers, especially for men. From 1984 to 2004 the percentage of head and neck cancers related to HPV jumped from 16% to 70%.
While there are more than a 100 types of HPV, there are several strains (HPV 16 and HPV 18 in particular) that are particularly cancer causing both above or below the belt.
HPV is ubiquitous in the genital tract. If you are a woman and you are sexually active there is a 70% chance you will have been infected by the age of 22. The good news is most people clear their HPV infection. It’s the infections that the immune system can’t clear that are at risk of progressing to disease (either cancer or genital warts, the other manifestation of genital HPV infection). Regardless, while your body is working to get the infection under control you can spread the virus through sexual contact.
So what about the mouth?
We know oral sex is a risk factor for HPV-related head and neck cancers. If you have had oral sex with 6 or more partners your risk of head and neck cancer increases 8-fold.
A study just published in JAMA (Gillison et al, January 26, 2012) evaluated more than 5,000 people for oral HPV. They collected a lot of demographic data to try to determine risk factors.
- 6.9% of people ages 14-69 have an active HPV in their mouth
- The peak prevalence of oral HPV infection is ages 30-34 and 60-64
- Men are more likely to have oral HPV than women (10.1% vs. 3.6%)
- Sexual contact is a risk factor for oral HPV: 0.9% of people who have never had sexual contact had HPV versus 7.5% who had ever been sexually active.
- The number of oral sex partners has a big effect on oral HPV. The prevalence is basically the same for 0 or 1 oral sex partner (3.5% and 3.3% respectively), but by the time you hit 21 or more sexual partners the prevalence of oral HPV jumps to 21.5%
So what about kissing? (Sometimes when I pull these studies I think, gosh, I’d just rather not know…).
To me, the data in the JAMA study suggests oral sex is not the only method of transmission because 0.7% of those had never been sexually active at all and 3.5% of those who said they had never had oral sex were HPV positive. I suppose it’s possible that participants weren’t completely honest about whether they had engaged in sex or oral sex, but the study used NHANES participants and the data is generally high quality. So if oral sex wasn’t involved in transmission for the non sexually active/non oral sexually active participants, well, what was?
The studies are sparse. One small study looking at men only, published in 2009 (Journal of Infectious Diseases), tells us that for men “open mouth kissing” with 10 or more partners is associated with an increased prevalence of oral HPV. It’s not a huge study and it has limitations, but, well, there you have it. By no means am I saying that open mouth kissing is a major route for oral HPV transmission, but it definitely suggests we need more studies.
Whether the HPV vaccine will help with prevention of oral HPV remains to be seen; however, the editorial that accompanied the JAMA article pointed out that in an animal study a HPV vaccine was able to prevent oral infections. In addition, fewer genital infections (due to vaccination) should translate into fewer oral infections given the known oral sex connection.
Why are we seeing more HPV-related head and neck cancers? I have a hard time accepting it’s all oral sex, since I’m pretty sure oral sex wasn’t invented in the last 20-30 years. Although, studies suggest there is more oral sex happening earlier (20% of kids in grade 9 have tried oral sex!), so perhaps adolescence is a more vulnerable time for oral HPV exposure. Smoking was also major cause of head and neck cancer and there are fewer smoking related cancers, so percentage wise HPV is now a bigger player. It is also possible other environmental co-factors are involved. Again, more studies are needed.
What we know for sure:
The more oral sex partners you have, the more likely you are to get HPV in the mouth. Like genital infections, most oral HPV will clear, but persistent infections increase your risk of head and neck cancer. Seventy percent of head and neck cancers in men are now HPV related.
Where STDs are concerned, fewer partners is safer. If you are going to have multiple oral sex partners, use a barrier method. Studies are conflicting about their effectiveness, but some protection is better than no protection.
The HPV vaccine reduces your chance of having cervical and anal cancers.
And while oral sex might not get you pregnant, it should be considered sex because it certainly has all the same infection related risks.