The sexually transmitted human papillomavirus causes some throat cancers in men and women, and oral sex increases the risk, U.S. researchers say. 

In Thursday's New England Journal of Medicine, Dr. Maura Gillison of Johns Hopkins Bloomberg School of Public Health in Baltimore, Md., and her colleagues studied 100 men and women newly diagnosed with oropharyngeal cancer in the tonsils, back of the tongue and throat.

The group was compared with 200 others without cancer.

Participants showing evidence of prior infection with HPV were up to 32 times more likely to develop the cancer, based on an analysis of blood and saliva samples.

Evidence of the HPV-16 strain of the virus was found in 72 per cent of tumours. Most HPV infections clear with little or no symptoms.

"People should be reassured that oropharyngeal cancer is relatively uncommon, and the overwhelming majority of people with an oral HPV infection probably will not get throat cancer," Gillison said in a release.

Consistent condom use may reduce risk, the team said.

In an anonymous survey, those who reported having more than six oral sex partners in their lifetime were the most likely to develop the HPV-linked cancer, the researchers found.

Oral sex is the main way oral HPV infection spreads, but mouth-to-mouth transmission has not been ruled out.