An estimated 1 million young Californians had a sexually transmitted disease in 2005, including 1 in every 4 or 5 young people in Los Angeles County, researchers said Tuesday.
"We were expecting high numbers . . . but this was a shock even to us," said epidemiologist Petra Jerman of the Public Health Institute in Oakland, who led the new study reported in the California Journal of Health Promotion. "It is clear we are living in the dark about how common STDs are and how many kids acquire them in a given year."
The report also highlights the large number of new cases of chlamydia and gonorrhea -- which are associated with HIV and are considered to be among the most serious STDs -- among people age 15 to 24, said Dr. Jonathan Fielding, director of the Los Angeles County Department of Public Health.
"It's really disturbing that we have not been able to make more progress with that," he said. "We don't have young people using protection when they are having sex."
The new study, the first of its kind, also found that the direct cost of treating the new infections is more than $1 billion per year.
"We've seen the human toll, but this provides the first estimate of the enormous economic cost that is borne in California due to STDs," said Dr. Peter R. Kerndt, director of the county's sexually transmitted disease program.
The incidence of the infections was not known previously because many of them -- including genital herpes, human papilloma virus and trichomoniasis -- do not have to be reported to public health authorities.
Many that should be reported are not because of incomplete screening of at-risk populations, underreporting of infections by medical and laboratory providers, and infections that are treated without a confirmatory test.
Jerman and her colleagues used a new computer model developed by the U.S. Centers for Disease Control and Prevention to estimate the incidence of STDs. Using the technique, CDC researchers reported in 2004 that 9.1 million new STDs occurred nationwide among 15- to 24-year-olds in the year 2000 with a direct medical cost of $6.5 billion.
Using the technique, Jerman and her colleagues estimated that there were 1.1 million new cases of STDs in California in that age group in 2005, with a cost of $1.1 billion.
HPV (590,000) and trichomoniasis (250,000) infections accounted for most of the infections, with chlamydia (180,000) a distant third.
