So funds and campaigning against HIV is finally showing its results.
Countries in Sub-Saharan Africa are leading a global decline in new HIV infections, the UN has said.
UNAids said 22 countries in the world's worst affected region had seen a drop in new cases of more than 25%.
The fall was because of greater awareness and better use of preventative measures, it said.
But UNAids also noted that cases of HIV were increasing in Eastern Europe and Central Asia, and among gay men in developed countries.
Michel Sidibe, UNAids executive director, said the world was making "real progress" towards achieving the sixth Millennium Development Goal (MDG6) of halting and reversing the spread of HIV/Aids by 2015.
"For the first time change is happening at the heart of the epidemic. In places where HIV was stealing away dreams, we now have hope," he said.
UNAids says there are now 5.2 million people worldwide receiving treatment for HIV/Aids, which has helped to ensure that 200,000 fewer people died from the virus in 2008 than in 2004.
The agency said young people "are leading the prevention revolution by choosing to have sex later, having fewer multiple partners and using condoms, resulting in significantly fewer new HIV infections in many countries highly affected by Aids".
The use of male condoms has also doubled in the past five years, while the report notes that "tradition is giving space to pragmatism" in many communities as they embrace male circumcision, which research shows has the potential to reduce HIV infections among men by nearly 60%