Since 1987, the U.S. Census Bureau and the U.S. Agency for International Development have compiled "information from ... small-scale surveys on the AIDS pandemic and HIV seroprevalence (infection) in population groups in developing countries." Statistics on HIV/AIDS in the United States are available from the Centers for Disease Control.
PAHO "provides technical cooperation and mobilizes partnerships to improve health and quality of life in the countries of the Americas." This website includes links to data and statistics, health topics, and publications.
The GHO data repository contains an extensive list of indicators, which can be selected by theme or through a multi-dimension query functionality. It is the World Health Organization's main health statistics repository.