The National Youth Risk Behavior Survey, released by the Centers for Disease Control and Prevention on Tuesday, analyzed 20 years of national HIV-related risk behavior data on U.S. high school students primarily between the ages of 14 and 17.

It found that while progress was made in the 1990s, when a decline was seen in the number of students who admitted to having multiple sexual partners, those rates have largely held steady since 2001.

The proportion of high school students who said they had ever had sex declined from 54 percent to 46 percent between 1991 and 2001, and then flat-lined at 47 percent in 2011. Among sexually active teens, condom use stabilized to about 60 percent in the years 2003 to 2011, compared with 46 percent in 1991.

The data was released in conjunction with the International AIDS Society's annual conference in Washington.

"We have to think about opportunities either to redouble our efforts or refine our efforts to get back on track," said Kevin Fenton, director of CDC's National Center for HIV/AIDS/Viral Hepatitis, STD and Tuberculosis Prevention.

Laura Kann, a senior CDC scientist who has led the survey since its inception in 1987, said the latest results gave reason for concern, as recent statistics showed that 40 percent of all new HIV infections are occurring among people under the age of 30.

In all, an estimated 1.1 million Americans are living with the human immunodeficiency virus that causes AIDS.

"Too many high school students in this country are at risk for HIV because they have had sexual intercourse, had multiple sex partners and are having unprotected sexual intercourse without a condom," she said. "Any kid that is practicing those behaviors is putting themselves at risk."

IMPROVEMENT AMONG BLACK STUDENTS

The survey data pointed to one area of improvement - a significant decline in sexually risky behavior among black high school students in the past 20 years.

While black youth still show higher rates of risky behavior than their peers, the narrowing gap between black and white youth shows that investments in sexual education and HIV prevention efforts can have an effect, Fenton said.

In 1991, 82 percent of black students said they had had sex, and that figure declined to 60 percent by 2011. The number who reported multiple sexual partners fell from 43 percent to 25 percent.

In that same period, the proportion of white students who reported ever having sex fell from 50 percent to 44 percent, and those who said they had multiple partners fell from 15 percent to 13 percent.

At the same time, Hispanic students have seen little change in the number who reported having had sex - from 53 percent in 1991 to 49 percent in 2011 - or who said they have had multiple sex partners.

"At a time when we know there are tremendous health inequities associated with HIV, data that suggests that we are moving in the right direction to reduce some of these inequities - that's a good-news story and we need to learn why this is occurring and see what more we can do to support that trend," he told Reuters.

However, such efforts already are threatened. In the past decade, the number of U.S. high school students who have been taught about HIV and received sexual education in schools has declined steadily due to budget cutbacks.

Also, in a society where HIV is no longer seen as the major public health threat it once was, it is easy for complacency to set in, Fenton and Kann said.

The CDC also is grappling with spending cuts and is expected to reduce its budget for HIV and sexual education programs by 25 percent next year.

"School-based investments have taken a hit," Fenton said. "Clearly with a cut of that nature you have to make some tough choices and we're going to have to be creative about how we think of funding programs in the future."

(Editing by Michele Gershberg, David Brunnstrom and Bill Trott)

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