ATLANTA (AP) — The sexually transmitted virus that causes cervical cancer in women is poised to become one of the leading causes of oral cancer in men, according to a new study published Friday in the Journal of Clinical Oncology.

HPV now causes as many cancers of the upper throat as tobacco and alcohol, probably due both to an increase in oral sex and the decline in smoking, researchers say.

The only available vaccine against HPV, made by Merck & Co. Inc., is currently given only to girls and young women. But Merck plans this year to ask government permission to offer the shot to boys.

Experts say a primary reason for male vaccinations would be to prevent men from spreading the virus and help reduce the nearly 12,000 cases of cervical cancer diagnosed in U.S. women each year.

Merck's vaccine, approved for girls in 2006, is a three-dose series priced at about $360. Government officials and the American Cancer Society say they don't know yet whether Merck's vaccine will be successful at preventing disease in men. No data from the company's study are available yet.