SAO PAULO (AP) — The devastating news didn't make sense to Brazilian Pierre Freitaz. How was it possible that, at age 17, he was infected with HIV if his only boyfriend seemed fit and healthy?

Freitaz confesses he knew little about the virus when he was diagnosed in 2004. He didn't understand the difference between the infection and the disease it caused: AIDS. He was confused by the lack of obvious symptoms.

"It's like I was living in a different part of the world, and I felt immune."

While Brazil has long been seen as a global model in the fight against AIDS, activists and officials say more and more youths share Freitaz's unawareness of HIV risks, or are unconcerned about them. Even as HIV infection rates have begun declining in many other places, cases have been slowly rising in Brazil — with the sharpest jump among youths 15 to 24.