ATLANTA - Doctors have known for some time that a sexually spread virus can cause some types of oral cancer. But actor Michael Douglas' comments on his own throat cancer in a newspaper story Monday threw a spotlight on the subject. And it raises a lot of questions:

• What virus can cause oral cancer?

HPV, the human papillomavirus. It's best known for causing cervical cancer and genital warts. It also can be spread by oral sex, and men are more susceptible than women. It is a growing cause of certain types of oral cancer - those in the upper throat, at the base of the tongue and in the tonsils.

Indeed, studies suggest that HPV can be blamed for 60 percent to 80 percent of cancers of the upper throat.

• What happened to Douglas?

In 2010, Douglas announced that after seeking treatment for a very sore throat, he was diagnosed with a tumor at the base of his tongue. Because of the location of the cancer, some experts had wondered if it was related to HPV, but Douglas had a history of smoking and drinking and did not go into detail.

The 68-year-old Douglas has been free of cancer for more than two years after receiving extensive chemotherapy and has returned to acting. On Monday, The Guardian newspaper in England published an interview Monday in which Douglas said HPV is a cause of his cancer.

• What's the risk of getting oral cancer from performing oral sex?

About 2.5 million Americans are estimated to have oral HPV infections. But only about 14,000 cases of that type of cancer are expected this year, suggesting the risk of developing this cancer is low.

The virus is hard to avoid. As many as 75 percent of sexually active men and women will be infected with it at some point. Most people clear the infection on their own within two years. Some, however, have difficulty ridding themselves of HPV. And in some cases, the virus creeps down through tiny fissures in the base of the tongue or in the tonsils to lodge deep in the tissue.

• Men are at greater risk?

Apparently, yes. A small study in Baltimore found men accounted for about 85 percent of recent HPV-related oral cancers, said Dr. Sara Pai, a Johns Hopkins University researcher.

Experts believe men have lower amounts of antibody protection against HPV, she added.

• What should I do if my girlfriend or boyfriend has an HPV infection?

Abstain from oral sex, experts advise, though if you've had sex you likely were already infected. And use condoms during vaginal intercourse.

• Isn't there a vaccine against HPV that's available to males?

Yes, but it's recommended for boys before they first have sex. Experts say it generally doesn't work after someone's already been exposed to HPV. There is some work being done on a therapeutic vaccine against HPV.

• Is the risk for oral cancer greater from tobacco or alcohol?

Tobacco especially has been fingered as the cause of most cancers in the head and neck, including in the voice box and at the front of the tongue. Alcohol is believed to be a contributor, too. But cancers of the upper throat are mainly tied to HPV.