Among the world's youth, HIV infection dropped by 12 percent over the last decade, says UNICEF report.
"Is it progress? Yes. Is it enough? Absolutely not," said Elhadj As Sy, UNICEF director for eastern and southern Africa, at the launch of the report in Johannesburg.
Five million people aged 15-24 have HIV, down 12 percent from 2001, but with 2,500 new infections daily, the report said.
Young women are hardest hit, representing more than 60 percent of all young people living with HIV -- a figure that jumps to 72 percent in sub-Saharan Africa.
African youth generally bear a staggering share of the burden and risk: close to four of the five million young people living with HIV are in sub-Saharan Africa, it said.
As Sy said early sexual debut, pregnancy and drug use are driving the spread of HIV among youth, and called on communities to address issues of teen sex and drug use.
"For too long, communities have turned a blind eye to some of the most difficult determinants of risk," he said.
"Here is now the time that we have the collective responsibility... to address these very difficult issues head-on."
The study also found most adolescents living with HIV do not know their status -- particularly troubling after a new research last month found that HIV-positive people who take anti-retroviral drugs cut their risk of spreading the virus by 96 percent.
Researchers said the report is the first study to look at HIV among young people.
It was published by seven international organisations including UN children's organisation UNICEF, the World Health Organisation and the World Bank, and comes a week before a UN high-level meeting on AIDS that will review progress in fighting the disease 30 years into the epidemic.