Oral human papillomavirus (HPV) infection is more common among men than women, leading to an increased risk for men of head and neck cancers, a US study suggests.
The Journal of the American Medical Association (JAMA) study assessed around 5,500 people aged 14 to 69.
Around 10% of men had oral HPV, compared with 3.6% of women.
HPV causes the majority of cervical cancers, as well as genital and anal - and head and neck cancers.
Smoking and drinking are significant known risk factors for head and neck cancers. But oral HPV infection increases cancer risk by around 50%, according to the research team from Ohio State University Comprehensive Cancer Center.
They say the incidence of head and neck cancers has significantly increased over the last three decades, and HPV has been directly implicated as an underlying cause.
The researchers used data from a cross-sectional study as part of the 2009-10 National Health and Nutrition Examination Survey.
They all provided a skin cell samples for testing from their mouths, and were interviewed about their lifestyles and sexual history.
Overall prevalence of oral HPV infection was 7%.
Prevalence of HPV increased with lifetime or recent number of partners for any kind of sex, vaginal sex, or oral sex.
Writing in JAMA, the team led by Dr Maura Gillison, said their findings should influence research into the existing HPV vaccines and how effective they could be in preventing oral cancers.
"Vaccine efficacy against oral HPV infection is unknown, and therefore vaccination cannot currently be recommended for the primary prevention of oropharyngeal cancer.
"Given an analysis of US cancer registry data recently projected that the number of HPV-positive oropharyngeal cancers diagnosed each year will surpass that of invasive cervical cancers by the year 2020, perhaps such vaccine trials are warranted."
Jessica Harris, health information manager at Cancer Research UK, said: "As we learn how common HPV infections in the mouth are, and how they are passed on, we can understand more about who is most at risk and how people can reduce the risk of HPV-related cancers.
"Although there isn't yet any evidence to show whether HPV vaccination is effective at preventing oral HPV infections, results like these are vital to help inform prevention programmes in the future."