AIDS
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 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 who were nostalgic about the 20th and early 21st centuries had never heard of AIDS, Africa 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)