16 million Americans have HPV in their mouths, mostly men

(CBS/AP) At least 50 percent of sexually active Americans will have genital HPV in their lives, according to government estimates. A new study suggests a lot of them might also have human papilloma virus in their mouths.

The study - which was the first nationwide estimate of how many people in the U.S. have oral human papilloma virus - found that 7 percent of Americans aged 14 to 69 are infected. That's 16 million people.

HPV is increasingly recognized as a major cause of oral cancers affecting the back of the tongue and tonsil area. Smoking and heavy drinking are also key causes.

Are the results cause for alarm? Not quite, according to experts. While mouth cancers are on the rise - probably from oral sex, HealthPop reported - most people with oral HPV will never develop cancer. And most don't have the kind most strongly linked to cancer. Also, tests for oral HPV are costly and mainly used for research purposes.

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Still, experts say the study provides important information for future research that could increase knowledge about who is most at risk for oral cancer and ways to prevent the disease.

For the nationally representative study - published in the Jan. 26 issue of the Journal of the American Medical Association - researchers gave 30-second gargle tests given to about 5,500 people during a 2009-10 government health survey. Their mouthwash samples were tested for HPV.

There are many types of HPV, but one strain in particular known as HPV-16 is most strongly linked with oral cancer and also is a common cause of cervical cancer. That strain was found in about 1 percent of people studied, translating to about 2 million Americans.

The study "provides us some reassurance" that most people with oral HPV will not get oral cancer, said Dr. Maura Gillison, the lead author and a researcher at Ohio State University. Millions may have oral HPV, but fewer than 15,000 Americans get HPV-linked oral cancer each year.

Gillison said the study should prompt research into whether the existing vaccines for cervical cancer protect against oral HPV, too. She has consulted with Merck & Co., and GlaxoSmithKline, makers of HPV vaccines. Ohio State, Merck and the National Cancer Institute helped pay for the study.

Dr. Ezra Cohen, a head and neck cancer specialist at the University of Chicago, said the study confirms similarities in risk factors for HPV oral infections and oral cancer. For example, oral HPV was more common in men than women - 10 percent versus almost 4 percent; in smokers; and in people who had many sexual partners. People aged 55 to 59 were most at risk.

Sexual activity was a strong risk factor, including oral sex.

Oral HPV infection rates were much lower than previous estimates for HPV affecting the cervix and other genital areas, suggesting that the mouth might somehow be more resistant to infection, according to an editorial in the journal.

The editorial's author, Dr. Hans Schlecht, an infectious disease specialist at Drexel University in Philadelphia, said the study provides fodder for researching how some infections lead to cancer and identifying ways to detect and treat HPV-related oral lesions before they turn into cancer.

Unlike non-HPV cancers easily seen in the front of the mouth, HPV-linked tumors in the rear tongue and tonsil area are often hard to detect.

Schlecht emphasized the importance of knowing symptoms of these cancers, which can include a sore throat, difficulty swallowing, ear pain and swollen lymph nodes in the neck. According to the National Cancer Institute, more than 39,000 new cases of oral cancer are diagnosed each year.