One in four teenage girls in the United States - and nearly half of African-American girls - has at least one sexually transmitted disease, according to a study released yesterday, providing the first national snapshot of infection rates among this age group.
Those numbers translate into an estimated 3.2 million adolescent females infected with one of the four most common STDs - many of whom may not even know they have a disease or that they are passing it to their sex partners.
"What we found is alarming," said Dr. Sara Forhan, a researcher with the Centers for Disease Control and Prevention and the study's lead author. "This means that far too many young women are at risk for the serious health effects of untreated STDs, including infertility and cervical cancer."
The study's authors analyzed data on 838 14- to 19-year-old females who participated in the 2003-2004 National Health and Nutrition Examination Survey, an annual study that assesses a broad range of health issues. For the analysis, the teens were tested for human papillomavirus, chlamydia, trichomoniasis and herpes. By far, the most common sexually transmitted disease was HPV. Of those infected, 15 percent had more than one STD.
"It shows that what people have always suspected is true," said Dr. Emily J. Erbelding, an infectious diseases specialist at Johns Hopkins Bayview Medical Center. "Sexually transmitted infections have been called a hidden epidemic because a lot of these conditions are going to be asymptomatic when they're diagnosed. ... But they're highly common."
The overall figures could be slightly higher since some sexually transmitted diseases - syphilis, HIV and gonorrhea - were not included in the study, though experts say the prevalence is low for those infections among adolescents. The study did not include teenage boys.
The paper is being presented tomorrow at a CDC conference on STD prevention in Chicago.
Forhan said she was surprised to see how readily the risk to young women appears. Of those in the study who said they had one sexual partner in their lifetime, the prevalence of STDs was 20 percent, she said.
While parents might be surprised by the study, it's a reflection of what doctors have been seeing in their practices in recent years, said Dr. Ligia Peralta, chief of the Division of Adolescent and Young Adult Medicine at the University of Maryland School of Medicine. In a small study in 2000 among girls at her university clinic, which serves primarily black teens, 90 percent of the sexually active teens had HPV.
Still, she called the CDC study "critical information for parents" and encouraged them to use this knowledge to be sure their daughters are being properly screened and taught about protection and prevention. She said parents need to know that the average age of a girl's first sexual intercourse is 15.
"Parents do not come with a manual to know exactly how to discuss this with their kids," she said. "This is the opportunity to do it. You just open up the door for communication." She said doctors are there to also have these conversations with teenage girls.
There are 19 million sexually transmitted diseases in the United States - costing the health care system $15 billion a year - and almost half occur among the 14 to 25 age group, said Dr. Kevin Fenton, director of the CDC's National Center for HIV/AIDS, Viral Hepatitis, STD and TB Prevention. CDC officials called STDs a public health epidemic and said efforts must be made to improve screening, education and other prevention strategies for sexually active teens.
"While the burden of STD is significant, it doesn't have to be," said Dr. John Douglas, director of the CDC's division of STD prevention.
He said the report highlights "extraordinary racial disparities" among those with sexually transmitted diseases. African-Americans make up 13 percent of the population, but make up 46 percent of the chlamydia cases, for example. He said the higher rates of infection do not necessarily mean there is more risky behavior among black teens, just that the teens are more likely to come into contact with a person with an STD because there is so much of it in the community.
The higher rates could be because of limited access to health care, which may result in delays in seeking care or in fewer visits to doctors for screening, he said.
Dr. Avril Melissa Houston, medical director of the Baltimore Health Department's division of youth and families, said that teenage girls are biologically more susceptible to sexually transmitted infections and that their bodies change as they become adults to make them less so. She said teens are also more likely to spread diseases around their social networks through short-lived relationships.
While abstinence is the safest option, she said teens need to be told about consistent and correct condom use, which can prevent many sexually transmitted infections.
Dr. Peter L. Beilenson, Howard County's health commissioner, said abstinence-only education isn't always realistic.
"Teenagers from time immemorial have been sexually active and we need as a society to help protect them," Beilenson said.
At least 50 percent of sexually active men and women have an HPV infection at some point in their lives, and much of it clears up on its own. Most people with HPV do not develop symptoms or health problems. But sometimes, certain types of HPV can cause genital warts in men and women while other HPV types can cause cervical or other cancers.
The CDC recommends that girls and women ages 11 to 26 be vaccinated against HPV.
The CDC also recommends annual chlamydia screening for sexually active women under the age of 25. The symptoms are often silent, and women might not know they have it. But left untreated, it can cause irreversible damage, particularly to fertility.
There are misperceptions about who is at risk - both among teens and health care providers, Douglas said. And there remains a taboo in many circles about discussing these infections.
Erbelding, at Bayview, said the results of the study should remind doctors and parents that girls as young as middle school age need to be prepared for all that comes with becoming sexually active.
"If their kids are going to be armed with the tools to protect themselves from pregnancy and STDs, the discussion needs to start before age 14," she said.