About 25,000 scientists, policymakers and physicians met here for the 17th International AIDS Conference in search of better ways to curb the spread of the epidemic.
It is the first time the biennial conference is held in Latin America. The gathering, with Universal Action Now as its theme, runs through Friday.
Some 2.1 million people died of AIDS last year and about 33 million people worldwide have the HIV infection, according to the UN.
In Latin America, at least 500,000 people aged between 15 and 24 are HIV carriers, a 5-percent increase over 2006 figures, the United Nations Population Fund (UNFPA) says.
Among the 33 million people in the world living with HIV/AIDS, 5.5 percent are teenagers and young adults, and about one third of them are Latin American, according to the UNFPA.