The dramatic increases in U.S. incidence of throat cancer can be attributed to infection with the human papillomavirus, U.S. researchers say. Senior author Dr. Maura Gillison of Ohio State University Comprehensive Cancer Center in Columbus and collected data from registries in three states. The researchers showed that the proportion of oral or throat cancers -- particularly among men -- tested positive for HPV increased from 16 percent of such cancers diagnosed during the 1980s to more than 70 percent diagnosed during the 2000s. Previous research showed oral cancers can be divided into two separate diseases with distinct causes -- HPV-negative cancers, which are associated with tobacco and alcohol use; and HPV-positive cancers, which are linked to certain types of HPV, a sexually transmitted virus. \"We used to think of oropharyngeal cancer as one cancer, and now we know the disease is comprised of two biologically and epidemiologically distinct cancers,\" Gillison said in a statement. On a population level, the research team discovered from 1988 to 2004, the incidence of HPV-positive cancers rose from 0.8 per 100,000 to 2.6 per 100,000 -- an increase of 225 percent, while HPV-negative oral cancer declined by 50 percent, probably due to declines in smoking and tobacco use, Gillison said. \"These increases may reflect increases in sexual behavior, including increases in oral sex,\" Gillison said.