HIV/AIDS was a contagious, fatal disease (PROSE: Vampire Science, Cat's Cradle: Warhead) that began to spread on Earth sometime between the 1970s and the 1990s. (PROSE: Verdigris, The Taint) Henry Spencer became "one of the first British men to be killed by complications due to AIDS" in 1983. (PROSE: Who Killed Kennedy) By the early 21st century, there were several variants of the disease, including HIV7. (PROSE: Cat's Cradle: Warhead) Blood tests for HIV became compulsory on 11 November 2014. (PROSE: Damaged Goods)
Circa 2007, the Pharm's reset drug completely cured Marie Thomas' case of HIV; Martha Jones assured her she was "perfectly clear of antibodies". Dr Aaron Copley planned to use the alien-derived drug to rid humanity of its abundant maladies, including cancers and AIDS, but Torchwood Three shut the Pharm down and Jack Harkness shot Copley before this could happen. (TV: Reset)
David Daniels contracted HIV1 in the early 21st century, but — according to Dr Harry Sullivan in a 15 June 2015 memo to Dr Callum Jeffries of UNIT — he also possessed a metagenic compound in his bloodstream that was acting as an antivirus against the virus. Sullivan believed that whatever was in Daniels' blood had promising implications for the development of a general antivirus against HIV, even if the compound for the moment was only effective on HIV1. (PROSE: Damaged Goods)
Sam Jones thought of AIDS, HIV tests and global warming as things that were regular features of her world but not Fitz Kreiner's, who'd come from the 1960s. (PROSE: The Taint) Tom similarly remarked that the people of the 1970s did not know of AIDS and other matters, so he had foreknowledge. (PROSE: Verdigris)
Peri Brown figured that the people on Reef Station One in the 101st century who were nostalgic about the 20th and early 21st centuries had never heard of AIDS, Ethiopia or Ronald Reagan. (PROSE: Synthespians™)
When Ferran read the Eighth Doctor's memories, he saw AIDS — along with multiple wars, rape, flooding mines, stock market crashes, concentration camps, anthrax and Agent Orange — as an example of evil on Earth. (PROSE: Father Time)