LAST YEAR, the Centers for Disease Control and Prevention declared a shift in HIV prevention strategy, placing more emphasis on reaching those already infected by the virus. The approach has some merit: It is now easier to identify HIV-positive people using newer, faster tests, and it is vital to educate them on how to avoid spreading the virus. But the CDC's implementation of its shift has resulted in halting federal support for key local HIV-prevention programs for teenagers, a shortsighted strategy that fails to acknowledge the importance of teaching young people how to be smart about HIV and AIDS -- before they are infected.

The problem is particularly worrisome in the Washington region, which has been hit hard by the AIDS epidemic. As reported by The Post's Arielle Levin Becker, four local youth-oriented HIV-prevention groups recently failed to win renewal of CDC grant funding; each had been receiving at least $200,000 annually. For Metro TeenAIDS, the rejection means fewer full-time staffers to go into schools; for the Sasha Bruce Youthwork agency, suspending an educational play about AIDS. The National Organization of Concerned Black Men has had to suspend its prevention programs primarily serving 15 Southeast District public schools. The Northern Virginia AIDS Ministry was forced to pull back its high school peer outreach and health education programs from Prince William County, affecting 6,400 teenagers. These valuable HIV-prevention programs are seeking help from city and county governments, along with private companies and nonprofits.

Preventing HIV infection requires that both HIV-positive and HIV-negative individuals know how to prevent the spread of the virus. Teenagers can't simply put their trust in people who are HIV positive to take the responsibility of getting tested, informing partners and preventing the infection of others. Educational programs that inform teens about the risks of HIV and AIDS are a critical part of any prevention strategy, especially in a city where three out of five high school students have sex and at a time when half of all new infections occur in people under the age of 25.

The CDC's Divisions of HIV/AIDS Prevention says that it has had to manage without any increases in funding for several years, despite increasing infection rates in certain at-risk populations. That should be a sign to Congress to increase funding. But in the meantime, even with limited resources, it is shortsighted to limit prevention efforts for young people. If the CDC says its goal is to focus prevention for people at high risk for HIV infection, surely that effort should include teenagers.