You might have seen the television advertisement: A teenage girl smiles as she picks up her cell phone. It's her friend, sending her a text message with the question, "Did you hear about Kim?"

It could be an ad for phones, except it turns out that Kim has HIV. How she got it is a bit unclear. "She got high, she got stupid, and now she has HIV."

The idea behind the public service announcement, which is sponsored by the National Institute on Drug Abuse, is that alcohol and any drug use, not just intravenous drug use, increase the risk for contracting HIV because people under the influence of drugs might be more likely to engage in risky sexual behavior.

"Text Message" features Zaibaa Mahdi and Rebecca Hollingsworth, students at the Duke Ellington School of the Arts. Hollingsworth got the part on her first day at school after moving from Metairie, La., after Hurricane Katrina. It began running a week ago as the institute launched a national public awareness campaign at the school on World AIDS Day. The institute wants the ad to reach people ages 13 to 24, a group it has identified as facing a growing risk of contracting HIV.

The ad is running on TV stations nationwide and at the Avalon Theatre in Northwest Washington. It will be shown in January on Times Square's Astrovision screen and in Circuit City, Best Buy, Costco and Sears stores. Print ads are up on Metrobuses and in transit systems in Chicago and Dallas.

The target age group represents a relatively small portion -- 4.7 percent in 2003 -- of new AIDS cases. After senior citizens, young people have the lowest incidence of AIDS diagnoses.

But 4.7 percent is a significant increase from the 3.9 percent measured in 1999. Ten people in the age group are diagnosed with HIV every day, according to a report by the institute.

Don Vereen, special assistant to the institute's director, said in an interview that dozens of studies have shown that drugs are involved in the lives of many people who contract HIV and that people younger than 20 use drugs the most.

The institute wants to stress the impact drugs can have on judgment about sexual practices before the rate of infection among the young gets worse. "We want to introduce this information early, not when the rate [of increase over one year] is 10 percent," he said.

In people 13 and older, intravenous drug use is responsible for 20 to 25 percent of new cases, according to the Centers for Disease Control and Prevention. The remaining new cases stem from other behaviors, primarily unprotected sex.

"When you talk to some of these folks, when the unprotected sex happens, it's often under the influence," Vereen said. "Teens are involved in sexual activity. They are involved in drug activity. When you put those together, you get a lot of the risks for contracting HIV."

The District has been hit particularly hard by AIDS. For every 100,000 city residents, 162 were diagnosed with the disease in 2002, compared with 15 nationally, according to the U.S. Health Department. An estimated one in 20 city residents is infected with the virus.

To illustrate the prevalence of HIV, volunteers from City Year AmeriCorps and Metro TeenAIDS called CSX HIV Outreach Prevention and Education conducted a "transmission game" at Duke Ellington's AIDS Day assembly.

Nine students were given a stack of colored stickers and yellow wristbands, which indicated they had HIV. The stickers meant exposure to the virus through different means: sharing of needles at a tattoo party, unprotected sex, getting high or drunk before having unprotected sex, and mother-to-child transmission.

Those with yellow wristbands were told to give three other students a sticker, then pass the stack of stickers to the third person to continue the cycle. Those who asked questions during discussions were given red wristbands to indicate that they used condoms and that their stickers did not mean they had contracted the virus. At the end of the game, more than 100 teenagers had been infected.

Volunteer Jeremy Kress said the game was based on actual infection rates in the District. "Sixty-five percent of high school students are sexually active. Sixty-five percent of those use condoms," he said.

Ruthie Yow, a volunteer who teaches HIV/AIDS awareness at Dunbar Senior High School and Hart Middle School, said that her experience indicates that middle and high schoolers often are in the dark about sex and the risks involved.

"I think one of the big problems is young people see themselves as immune or not at risk for something they don't often associate with heterosexual behaviors," Yow said. "High schoolers are overwhelmingly sexually active, and they're at risk. They're not aware how it's transmitted. We have high schoolers that don't know you can't get pregnant" from giving fellatio.

Although Mahdi knows a number of people who engage in unprotected sex, she doesn't think her classmates at Duke Ellington are ignorant about AIDS. "People I hang around with at my school know about it as much as I do," she said. "I was ignorant about it when I was much younger."

Although she believes the ad in which she starred is effective, Mahdi also took special note of a message delivered by Karlene Mighty, who is HIV-positive, during the program: "You don't have to be into drugs" to contract HIV, Mahdi said. "It could be someone really close to you. She said someone she was intimate with just didn't tell her."

Laughter and joking about the sexual habits of teenagers gave way to silence as Ellington students heard from an HIV-positive woman.A national public service announcement features Zaibaa Mahdi, a student at the Duke Ellington School of the Arts. She portrays a teenager who learns via a text message that a friend has HIV. Zaibaa Mahdi, left, and Rebecca Hollingsworth starred in the ad, which was screened at Duke Ellington. Alexander Duff, above, participates in a "transmission game" at the World AIDS Day program at the Duke Ellington School of the Arts. The red bracelets represented using a condom and thereby being protected from HIV. At left, Karlene Mighty, who is HIV-positive, talked about her experiences, warning students that they didn't have to be drug users to contract the disease.