At least one in four teenage American girls has a sexually transmitted disease, suggests a first-of-its-kind federal study that startled some adolescent-health experts.
Some doctors said the numbers might be a reflection of both abstinence-only sex education and teenagers' own sense of invulnerability. Because some sexually transmitted infections can cause infertility and cancer, U.S. health officials called for better screening, vaccination and prevention.
"STDs are occurring in teenagers, and they're occurring here in Tampa," said Dr. Catherine Lynch, director of the general obstetrics and gynecology division at the University of South Florida. "It's unfortunate that these things do happen. But as parents, we need to counsel our children, and counsel them appropriately so they can make good choices."
Only about half of the girls in the study acknowledged having sex. Some teens define sex as only intercourse, yet other types of intimate behavior including oral sex can spread some diseases.
Among those who admitted having sex, the rate was even more disturbing — 40 percent had an STD.
"This is pretty shocking," said Dr. Elizabeth Alderman, an adolescent medicine specialist at Montefiore Medical Center's Children's Hospital in New York. "To talk about abstinence is not a bad thing," but teen girls — and boys too — need to be informed about how to protect themselves if they do have sex, she said.
The overall STD rate among the 838 girls in the study was 26 percent, which translates to more than 3-million girls nationwide, researchers with the U.S. Centers for Disease Control and Prevention found. They released the results Tuesday at an STD prevention conference in Chicago.
Dr. Marcy Baker, a Tampa pediatrician, said the study may prompt more parents to get their daughters vaccinated for HPV, the human papillomavirus, which can cause cervical cancer and was the most common STD found in the study.
"This is an eye-opener for parents," Baker said. "These stats bring home the whole point of why we want to give the HPV vaccine early. … You don't want to gamble your child's health on when you think she might be sexually active."
Teens need to know specific information about preventing STDs, Lynch said.
"It's obvious to say that abstinence is your best choice," she said. "You need to be clear on what you're abstaining from. Oral sex is sex. Coming close, but not quite there, can transmit STDs."
Lynch said people underestimate their risk. "You see it in all socioeconomic segments of our society," she said.
Just last week, she treated a pregnant teenager who is HIV-positive.
Cecile Richards, president of Planned Parenthood Federation of America, said the study shows that "the national policy of promoting abstinence-only programs is a $1.5-billion failure, and teenage girls are paying the real price."
The new study by Dr. Sara Forhan, a CDC researcher, is an analysis of nationally representative records on girls ages 14 to 19 who participated in a 2003-04 government health survey.
The teens were tested for four infections: HPV, which affected 18 percent of girls studied; chlamydia, which affected 4 percent; trichomoniasis, 2.5 percent; and genital herpes, 2 percent.
Disease rates were significantly higher among black girls — nearly half had at least one STD, compared to 20 percent among both whites and Mexican-Americans.
The numbers in the CDC study are much higher than actual reported cases. For example, in Florida, the state says only 250 of 100,000 people have chlamydia, or 0.25 percent, a fraction of the 4 percent in the study.
But because so few people get tested for the disease, studies that screen all participants usually show much higher disease rates. Only about 1 in 10 people exposed to herpes know they've been exposed, Lynch said.
CDC spokeswoman Nikki Kay said, "Generally, we do see that many STDs do go undiagnosed, and screening is an under-used tool."
HPV, the cancer-causing virus, can also cause genital warts but often has no symptoms.
The CDC recommends the three-dose HPV vaccine for girls ages 11-12 and catchup shots for ages 13-26.
Chlamydia, which often has no symptoms but can lead to infertility, can be treated with antibiotics. The CDC recommends annual chlamydia screening for all sexually active women under age 25.
Trichomoniasis, also treatable with antibiotics, can cause abnormal discharge and painful urination. Genital herpes can cause blisters but often has no symptoms. It's not curable but medicine can help.
Teens need to hear the dual message that STDs can be prevented by abstinence and condoms, said Dr. Ellen Kruger, an obstetrician-gynecologist at Ochsner Medical Center in New Orleans.
"You've got to hammer at them," with appropriate information at each stage of teen development to make sure it sinks in, she said.
Times staff writer Lisa Greene contributed to this report.