According to a new study, STD is a huge and hidden epidemic throughout California with 10,270 of 113,000 teenagers and young adults in Ventura County contracting sexually transmitted diseases in 2005.

Statistical formulas previously used by the federal government show that the number of cases of Chlamydia, gonorrhea, HIV, HPV and similar diseases could be nearly nine times greater than the actual cases reported to health officials, said researchers at the Public Health Institute in Oakland.

Their study, published in the California Journal of Health Promotion, indicated there might have been more than 1 million such cases affecting young people throughout the state in 2005. That's 10 times more than the number reported.

The study estimates the state spent more than $1.1 billion in treating and diagnosing sexually transmitted diseases in young people in 2005. Researchers said as much as $9.9 million was spent in Ventura County.

The study suggests there may have been 2,900 new cases of HIV in 2005 throughout California for people 15 to 24. But only 516 cases were reported to health officials. That's not only alarming but also a compelling reason to screen everyone for the disease.

County health officials said that 1,165 sexually transmitted diseases were reported in 2005 for people 15 to 24, compared to the study's estimate of more than 10,000 total cases. The gap was even bigger statewide. Researchers estimated 1.1 million sexually transmitted diseases during the year, compared to about 102,000 reported cases.