A new study about the prevalence of oral HPV infection in the U.S. population may help health experts understand why rates of oropharyngeal cancer have skyrocketed in recent years.

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LOS ANGELES — An estimated 7 percent of American teens and adults — about 16 million people — carry the human papilloma virus (HPV) in their mouths, an infection that puts them at heightened risk of developing cancer of the mouth and throat, researchers said Thursday.

The study, the first to assess the prevalence of oral HPV infection in the U.S. population, may help health experts understand why rates of oropharyngeal cancer — a type of head and neck cancer — have skyrocketed in recent years, increasing 225 percent between 1988 and 2004. Smoking and heavy drinking are also key causes.

Until now, it was not known how many people have oral HPV infections.

The findings also indicate that the virus is not likely to spread through kissing or casual contact and that most cases of oral HPV can be traced to oral sex.

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“There is a strong association for sexual behavior, and that has important implications for public-health officials who teach sexual education,” said Dr. Maura Gillison of The Ohio State University Comprehensive Cancer Center, who led the study.

The study results were published online by the Journal of the American Medical Association on Thursday.

HPV is best-known as the cause of cervical cancer, which kills 4,220 women in the United States each year, according to the National Cancer Institute.

The virus can also cause vulvar, anal, penile and various head and neck cancers. A study published in October in the Journal of Clinical Oncology traced more than 70 percent of new cases of oral cancers to HPV infection, putting it ahead of tobacco use as the leading cause of such cancers.

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

If present trends continue, HPV will cause more cases of oral cancers than cervical cancer by 2020, according to the October study.

HPV infection is common; an estimated 80 percent of Americans have contracted the virus, Gillison said. It usually produces no symptoms and is typically cleared from the body through natural processes.

But persistent infections can cause cancer. Vaccines are available for children and young adults to prevent cervical and anal cancers caused by the most troublesome HPV strains.

The data raise a number of important issues, experts said. For example, while Pap tests can detect HPV infection and precancerous cells in the cervix, there is no such test for precancerous cells in the mouth. Researchers also wonder whether the HPV vaccine will protect against oral cancers, a question that could take years to answer.

Gillison has consulted with Merck and GlaxoSmithKline, makers of HPV vaccines. Ohio State, Merck and the National Cancer Institute helped pay for the study.

Material from The Associated Press is included in this report.

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