SAN DIEGO -- The cost of treating 15 - 24-year-olds for venereal disease in San Diego County in 2005 was $110 million, second only to Los Angeles County, it was reported Wednesday.

The estimated 85,000 teens and young adults diagnosed with sexually transmitted diseases were lower per capita in San Diego than the state average -- 17 percent, compared with 20 percent. However, diseases diagnosed in the county's youths and young adults are more expensive to treat, The San Diego Union-Tribune reported.

"San Diego (County) has a greater number of chlamydia, gonorrhea and AIDS cases in the state, and that drives the cost," Petra Jerman, a spokeswoman for the Oakland-based Public Health Institute, which issued the report, told the newspaper.

Those diseases are more expensive to treat than syphilis, human papillomavirus, genital herpes, hepatitis B and trichomoniasis, Jerman said.

She said 360,000 cases were reported in Los Angeles County, costing the county $390 million.

Statewide, an estimated 1.1 million STD cases were reported among young people in 2005, the last year for which figures were available. Direct medical costs totaled $1.1 billion, the Union-Tribune reported.

The research was funded by the California Wellness Foundation.

One oddity discovered by researchers: Orange County, similar to San Diego County in population and many other demographics, reported 53,566 STD cases among young people, almost 32,000 fewer than in San Diego County. The Researchers couldn't account for the difference, the Union-Tribune reported.

In Orange County, the cost of treating those patients was $57 million, the Union-Tribune reported.