One in four U.S. teenage girls has the virus that can cause cervical cancer or three other sexually transmitted infections, the Centers for Disease Control and Prevention found in the first such study of ages 14-19.

The data from a 2003-04 government survey indicated 3.2 million teenage girls are infected with either bacterial chlamydia (4 percent), parasitic trichomoniasis (2.5 percent), herpes simplex virus (2 percent) or human papillomavirus (HPV, 18 percent), which is associated with cervical cancer and genital warts.

The infection rate was 48 percent for blacks and 20 percent for both whites and Mexican-Americans, said the report released Tuesday, March 11.

"Those numbers are consistent with our numbers locally," said Bill Wharton of Public Health—Dayton and Montgomery County. "And in the four years since the survey, it's been pretty steady."

"We must continue developing ways to reach those most at risk," said Dr. John Douglas, who directs the CDC's division of preventing STIs. People's immune systems eliminate the HPV infection naturally within two years "in 90 percent of cases," the CDC Web site says, but the virus can be transmitted during that time even without symptoms. The other infections can cause infertility and pelvic inflammatory disease if untreated.

"One of our greatest frustrations in public health is the difficulty in getting through to people when we explain how these infections are acquired and how to prevent them," Wharton said. "We tell them exactly how to have protected sex, and they're back in a few weeks with a new infection from the same partner."

There are two options for prevention, he said — abstinence or protected sex, in order of effectiveness. "We understand that most people prefer the protected-sex option. But if that's the option you choose, you have to follow the what you have to do for protected sex. You can't use the same practices as before and expect different results."

Contact this reporter at (937) 225-2129 or klamb@DaytonDailyNews.com.