The sexually transmitted human papillomavirus, already shown to cause nearly all cases of cervical cancer, also may cause cancer of the mouth and oropharynx, the part of the throat including part of the tongue and the tonsils, Reuters Health reports. Researchers in Costa Rica discovered HPV genetic material in about 4% of mouth cancer tumors and 18% of oropharynx tumors during a study of more than 1,400 oral cancer patients. Almost all of the HPV DNA was shown to be from the HPV-16 strain of the virus, which is the viral strain also linked with cervical cancer development. HPV DNA was detected at a high frequency among cancer patients who said they regularly practiced unprotected oral sex, suggesting that bodily fluids shared during oral sex may expose mouth tissues to the STD and fuel the development of oral cancers. The researchers say they hope HPV vaccines currently in development will be effective at preventing both cervical and oral cancers. Their full study can be seen in the latest edition of the Journal of the National Cancer Institute.