A study out yesterday in The Lancet by Moffitt Cancer Center researcher Anna Giuliano, Ph.D., and her colleagues finds that 50 percent of men ages 18 to 70 in Brazil, Mexico, and the U.S. have genital infection with human papillomavirus, or HPV. HPV is the virus that causes cervical cancer in women. It also causes warts and cancer of the genitals and anus in both men and women. Over the past several years, researchers have realized that the virus can also cause cancer of the head and neck.

Aimee R. Kreimer, Ph.D., of the National Cancer Institute, estimates that about 65 percent of the approximately 8,000 cancers of the oropharynx (tonsils and base of the tongue) seen in the U.S. in 2010 were from HPV infection; 80 percent of these are in men. The rates for HPV-associated cancers like these are increasing; for sites like the mouth and larynx that are associated with tobacco and alcohol use, the rates are decreasing (though still too high since too many people still smoke and abuse alcohol).

An infection rate of 50 percent for a virus that can cause cancer sounds scary. But knowing a few more facts about HPV helps put the risk in perspective. About 90 percent of men and women infected with HPV virus get rid of it on their own within about two years. There are many different strains of HPV -- some that cause cancer and some that don't. Only about 6 percent of men have genital infection with HPV 16 -- the strain linked to more than 90 percent of cancers of the head and neck. And only about 0.6 percent of men have HPV 16 in specimens taken from their mouths; what percentage of those men go on to develop head and neck cancer is unknown.

Right now, there are many more questions than answers. How exactly does HPV get from the genitals to the mouth? Oral sex is one obvious answer but the virus may also be spread by the fingers, kissing, or some other unsuspected route. Why does the infection persist in 10 percent of people?

What's urgently needed is some way of detecting the virus early -- the oral equivalent of a Pap smear. Researchers are trying to develop such a test at centers like Johns Hopkins, where earlier this month I interviewed a 64-year-old man whose HPV-linked tongue cancer was picked up only incidentally because he happened to go to an ear, nose, and throat doctor to get ear wax removed. There's got to be a better way of picking up asymptomatic HPV infection of the head and neck - before it progresses to cancer.

Finally, today's study is sure to provoke discussion about whether an HPV vaccine like Gardasil should be routinely recommended by public health officials for males as it is for females. The vaccine covers four strains of HPV, including strain 16, the one most commonly linked to head and neck cancer. Right now, the CDC supports "permissive use" of the vaccine in males 9-26 but stops short of actually recommending its use.

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