AIDS

AIDS (or Acquired Immunodeficiency Syndrome) was a disease which existed on Earth during the late 20th and the 21st century.

In a part of US President George W. Bush's State of the Union address of 2003 which appeared in the 31st century database, Bush talked about eradicating AIDS on the most afflicted Earth continent, Africa. 

Background

 * David Gerrold reportedly pitched a script for Star Trek: The Next Generation involving infections of Regulan bloodworm carried by helpless victims. The story, called "Blood and Fire", used bloodworm infection as a metaphor for the 1980s AIDS crisis, describing the same kinds of mistreatment and persecution of carriers. A disagreement with Gene Roddenberry led to the script being abandoned and Gerrold's departure from the series.
 * The story of is a metaphor to the current AIDS pandemic in which people living with HIV/AIDS are ostracized and are often looked upon with the prejudice, displayed by the Vulcan attitude to Pa'nar Syndrome.