According to data from the U.S. Centers for Disease Control and Prevention for 2001 to 2005 (the latest years available), the number of new cases of HIV infection diagnosed among 15-to-19-year-olds in the United States rose from 1,010 in 2001, held steady for the next three years, then jumped 20 percent in 2005, to 1,213 cases.
For young people aged 20 to 24, cases of new infection have climbed steadily, from 3,184 in 2001 to 3,876 in 2005.
Experts say a number of factors may be at play, including the fact that many HIV-infected patients are now being kept healthy with powerful drugs -- making AIDS seem like less of a threat to young people than it did in the past.
"Certainly the 'scare factor' isn't there anymore," said Rowena Johnston, vice president of research at the Foundation for AIDS Research (amfAR) in New York City.
In the 1980s and early 1990s, the ravages of AIDS were apparent to most Americans -- either on their TV screens as high-profile celebrities succumbed to the disease, or as individuals lost friends or family members to HIV.
"To see people looking gaunt, skinny and skeletal, and to know that they were going to be dead soon," Johnston said. "It had a sobering effect."
The advent of antiretroviral drugs in the mid-1990s changed all that, however. "These days, for the most part, you can look at a person and not know that they even have AIDS," Johnston said.
That's making HIV seem like less of a threat to young people, said Martha Chono-Helsley. She's executive director of REACH LA, a Los Angeles-based nonprofit that helps disadvantaged youth understand and defend against threats like poverty, drug abuse and HIV.
"They're in this age group that feels they are invincible -- that it's never going to happen to them," she said. "Yes, they're getting all these messages from public schools on HIV and AIDS, but they've never actually seen what HIV has done, up close and personal."
Chris Blades, one of REACH LA's young, black "peer educators," said he's seen a kind of nonchalance towards HIV among the gay or bisexual men of color that he counsels.
"On a daily basis, they don't see their friends suffering from it, so it's not a major threat to them," said Blades, 21. "They're in that whole mindset of 'Oh, it can't happen to me, it will never happen to me.'"
But there has been a recent, troubling spike in new infections among gay men, young and old alike. According to the CDC, the rate of new cases of HIV infection linked to male-male sex held steady at around 16,000 cases between 2001-2004, then suddenly jumped to 18,296 in 2005.
Johnston and Chono-Helsley both point to advertisements for HIV-suppressing medicines as one possible contributing factor.
"In gay magazines, you now see [ads with] buff, handsome men climbing mountains, with some kind of quote about how 'I'm not letting HIV get in my way,'" Johnston said. "It sends the message that you, too, can be hot, buff and handsome, even with HIV."
HIV continues to cut a wide swath through young men and women in the black community, too. According to the CDC, the number of new infections actually dipped slightly for black Americans between 2001 (20,868 cases) and 2005 (18,121 cases). However, black men are still six times more likely than white men to contract HIV, and black women are 20 times more likely to acquire the virus compared to white women.