The Centers for Disease Control and Prevention
The Centers for Disease Control and Prevention (CDC) is one of the 13 major operating components of the Department of Health and Human Services (HHS), which is the principal agency in the United States government for protecting the health and safety of all Americans and for providing essential human services, especially for those people who are least able to help themselves.
The CDC has two useful entry pages for infromation about HIV/AIDS:
http://www.cdc.gov/hiv/resources/qa – Questions and Answers about AIDS and HIV Prevention
http://www.cdc.gov/hiv – The CDCs topic area about AIDS and HIV.
This information is free for public use.